Should you avoid meat for good health? How to slice off the facts from the fiction



Meat is a very popular food for most Americans. Its nutritional value is a topic of much debate.
puhhha/Shutterstock.com

Dariush Mozaffarian, Tufts University

More than half of Americans who make New Year’s resolutions resolve to “eat healthier.” If you’re one, you might be confused about the role meat should play in your health.

It’s no wonder you’re confused. One group of scientists says that reducing red and processed meat is a top priority for your health and the planet’s. Another says these foods pose no problems for health. Some of your friends may say it depends, and that grass-fed beef and “nitrite-free” processed meats are fine. At the same time, plant-based meat alternatives are surging in popularity, but with uncertain health effects.

As a cardiologist and professor of nutrition, I’d like to clear up some of the confusion with five myths and five facts about meat.

First, the myths.

Red meat, while very popular, has not been shown to have health benefits.
Natalia Lisovskaya/Shutterstock.com

Myth: Red meat is good for health

Long-term observational studies of heart disease, cancers or death and controlled trials of risk factors like blood cholesterol, glucose and inflammation suggest that modest intake of unprocessed red meat is relatively neutral for health. But, no major studies suggest that eating it provides benefits.

So, while an occasional serving of steak, lamb or pork may not worsen your health, it also won’t improve it. And, too much heme iron, which gives red meat its color, may explain why red meat increases risk of Type 2 diabetes. Eating red meat often, and eating processed meat even occasionally, is also strongly linked to colorectal cancer.

Myth: You should prioritize lean meats

For decades, dietary guidance has focused on lean meats because of their lower fat, saturated fat and cholesterol contents. But these nutrients don’t have strong associations with heart attacks, cancers or other major health outcomes.

Other factors appear more important. Processed meats, such as bacon, sausage, salami and cold cuts, contain high levels of preservatives. Sodium, for example, raises blood pressure and stroke risk, while the body converts nitrites to cancer-causing nitrosamines. Lean or not, these products aren’t healthy.

Myth: Focus on a ‘plant-based’ diet

“Plant-based” has quickly, but somewhat misleadingly, become a shorthand for “healthy.” First, not all animal-based foods are bad. Poultry and eggs appear relatively neutral. Dairy may have metabolic benefits, especially for reducing body fat and Type 2 diabetes. And, seafood is linked to several health benefits.

Conversely, many of the worst foods are plant-based. Consider white rice, white bread, fries, refined breakfast cereals, cookies and so on. These foods are high in refined starch and sugar, representing 42% of all calories in the U.S., compared to about 5% of U.S. calories from unprocessed red meats, and 3% from processed meats.

Either a “plant-based” or omnivore diet is not healthy by default. It depends on what you choose to eat.

Myth: Grass-fed beef is better for your health

Conventional livestock eat a combination of forage (grass, other greens, legumes) plus hay with added corn, soy, barley or grain. “Grass-fed,” or “pasture-raised,” livestock eat primarily, but not exclusively, forage. “Grass-finished” livestock should, in theory, only eat forage. But no agency regulates industry’s use of these terms. And “free range” describes where an animal lives, not what it eats.

“Grass-fed” may sound better, but no studies have compared health effects of eating grass-fed versus conventional beef. Nutrient analyses show very modest differences between grass-fed and conventionally raised livestock. You might eat grass-fed beef for personal, environmental or philosophical reasons. But don’t expect health benefits.

Myth: Plant-based meat alternatives are healthier

Products like Impossible Burger and Beyond Meat are clearly better for the environment than conventionally raised beef, but their health effects remain uncertain. Most nutrients in plant-based alternatives are, by design, similar to meat. Using genetically engineered yeast, Impossible even adds heme iron. These products also pack a lot of salt. And, like many other ultra-processed foods, they may lead to higher calorie intake and weight gain.

So, what are the facts?

Sausages wrapped in bacon are a double whammy of unhealthy meat, as both bacon and sausage are processed meats.
MShev/Shutterstock.com

Fact: Processed meats are bad for health

Processed meats contain problematic preservatives. Even those labeled “no nitrates or nitrites added” contain nitrite-rich fermented celery powder. A current petition by the Center for Science in the Public Interest asks the FDA to ban the misleading labeling.

Besides the sodium, nitrites and heme, processed meats can contain other carcinogens, produced by charring, smoking or high-temperature frying or grilling. These compounds may not only harm the person who eats these products; they can also cross the placenta and harm a fetus.

Fact: A meatless diet is not, by itself, a healthy diet

Most diet-related diseases are caused by too few health-promoting foods like fruits, nuts, seeds, beans, vegetables, whole grains, plant oils, seafood and yogurt. Additional health problems come from too much soda and ultra-processed foods high in salt, refined starch or added sugar. Compared to these major factors, avoiding or occasionally eating unprocessed red meat, by itself, has modest health implications.

Fact: Beef production is devastating the environment

In terms of land use, water use, water pollution and greenhouse gases, unprocessed red meat production causes about five times the environmental impact of fish, dairy or poultry. This impact is about 20 times higher than that of eggs, nuts or legumes, and 45 to 75 times higher than the impact of fruits, vegetables or whole grains. A 2013 UN report concluded that livestock production creates about 15% of all global greenhouse gas emissions, with nearly half coming from beef alone.

Fact: Plant-based meats are better for the environment

Production of plant-based meat alternatives, compared to conventional beef, uses half the energy, one-tenth of the land and water, and produces 90% less greenhouse gas. But, no studies have yet compared plant-based meat alternatives to more natural, less processed options, such as mushrooms or tofu.

Fact: Many questions remain

Which preservatives or other toxins in processed meat cause the most harm? Can we eliminate them? In unprocessed red meats, what exactly increases risk of Type 2 diabetes? What innovations, like feeding cows special strains of seaweed or using regenerative grazing, can reduce the large environmental impacts of meat, even grass-fed beef? What are the health implications of grass-fed beef and plant-based meat alternatives?

Like much in science, the truth about meat is nuanced. Current evidence suggests that people shouldn’t eat unprocessed red meat more than once or twice a week. Grass-fed beef may be modestly better for the environment than traditional production, but environmental harms are still large. Data don’t support major health differences between grass fed and conventional beef.

Similarly, plant-based meat alternatives are better for the planet but not necessarily for our health. Fruits, nuts, beans, vegetables, plant oils and whole grains are still the best bet for both human and planetary health.

[ You’re smart and curious about the world. So are The Conversation’s authors and editors. You can read us daily by subscribing to our newsletter. ]The Conversation

Dariush Mozaffarian, Dean of Nutrition Science and Policy, Tufts University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Hot and bothered: heat affects all of us, but older people face the highest health risks



Older people’s bodies can’t regulate their temperature as well as younger people’s.
From shutterstock.com

Arnagretta Hunter, Australian National University

Australian summer temperatures have risen by 1.66℃ over the past 20 years. In the past century we’ve seen a significant increase in the number, intensity and duration of heatwaves during our summers.

Heat is the natural hazard associated with the highest mortality in Australia. When heatwaves occur, the death toll routinely reaches into the hundreds. For example, the 2009 heatwave across southeast Australia resulted in close to 500 deaths.

Heat is more likely to endanger the health of people with pre-existing conditions, people who are socially isolated, and people who have limited access to air conditioning. These are often older members of the community.




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Heat affects people of different ages in different ways

Human body temperature is set at 36.8℃, although our normal temperature can vary slightly and may marginally decrease as we age.

Ambient temperatures well below this prompt us to keep ourselves warm, and as the temperature rises we look for ways to keep ourselves cool.

An important mechanism of cooling is perspiration. As sweat evaporates, it cools our skin. However, humid weather impedes our capacity to cool ourselves in this way.

Heat stress occurs when the body can’t cool itself and maintain a healthy temperature. Heat stress can begin at temperatures around 30℃ when the humidity is high, and at temperatures closer to 40℃ in dry heat.




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Babies and young children are highly vulnerable to the heat because of their small size. They can become dehydrated and develop heat stress more quickly than adults.

This is because they absorb heat faster, and often cannot remove themselves from hot environments. So little ones need to be kept cool and well hydrated (with milk for babies and water for small children) during hot periods.

Babies and young children can become dehydrated more quickly than adults.
From shutterstock.com

While young people and adults face lower health risks from the heat, extended periods of hot weather can adversely affect our mood. One recent study pointed to increased intimate partner violence during heatwaves.

This effect appears to be exacerbated when night time temperatures are also high. High overnight temperatures are associated with increased crime rates, decreased productivity and poorer academic results.

But generally, it’s people over 65 who are at highest risk from the heat.

How does heat affect older people’s health?

The ageing body doesn’t cope with sudden stresses as quickly or effectively as a younger body. For example, an elderly person’s skin does not produce sweat and cool the body as efficiently as a younger person’s skin.

Importantly, heat stress can exacerbate existing health conditions common in older people, such as diabetes, kidney disease, and heart disease. Many heat deaths are recorded as heart attacks.

In short, this is because heat requires our hearts to work harder. In very hot conditions, our blood vessels dilate, increasing our heart rate. For people with abnormal heart function, these hot periods can lead to worsening of their heart failure.

With severe, prolonged heat stroke, heart failure can even develop in people without pre-existing heart disease.




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For people with pre-existing kidney disease, dehydration during hot periods can impact their kidney function. So people with kidney disease need to take extra care to stay hydrated during hot periods.

Dehydration can also affect older people’s blood pressure, making falls more likely.

Further, hot weather can affect blood sugar control for people with diabetes. Heat stress can increase blood sugar levels even in people without diabetes, but is most concerning in those with the condition. Poor blood sugar control is associated with many different diabetes complications including increased risk of infections.

Hot weather can indirectly affect health if the heat means not being able to exercise.
From shutterstock.com

Older people with chronic medical problems usually take regular medications. Some medications can hinder the body’s ability to regulate temperature and make people more susceptible to heat stress.

For example, people with heart failure often take diuretic medications to manage symptoms like swelling and shortness of breath. But increasing diuretic medications in hot weather can cause dehydration, worsening heart failure and often affecting the kidneys.

Added to this, heat stress may cause disorientation, confusion and delirium. This risk is more pronounced for older people with cognitive conditions and dementia.

Social factors and exercise

Socioeconomic factors and isolation can magnify the risk of heat exposure among older people. For example, some pensioners may not be able to afford air conditioning at home.

Being part of social networks can help. One person may recognise if another is unwell, increasing the likelihood of their friend getting medical attention.




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Further, extended periods of hot weather can interrupt our exercise routines. This can be particularly problematic for older people who may be using exercise to manage chronic health conditions.

Regular exercise correlates with improved quality of life in many conditions, including heart failure, chronic obstructive pulmonary disease, depression, diabetes, cognitive impairment and osteoporosis.

When our activity is disrupted for weeks at a time it can be hard to regain previous fitness. This can be especially true for older people, as muscle mass is commonly lost as we age. Periods of inactivity accelerate muscle loss, and regaining strength and endurance is often more difficult in this context.




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Australia’s climate is changing. We’re likely to experience longer periods of hot temperatures, with hotter summers and some extraordinarily high temperatures. This will test our health and our health-care systems. Understanding the challenge ahead can help to reduce the risks.

On a practical level, be aware of spending too much time in hot temperatures, stay hydrated, and know where you can access air conditioning – particularly if power fails. Consider vulnerable relatives, friends and neighbours, especially those of advanced age.The Conversation

Arnagretta Hunter, Physician & Cardiologist, The Canberra Hospital; Clinical Senior Lecturer, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

What causes hangovers, blackouts and ‘hangxiety’? Everything you need to know about alcohol these holidays



There’s no way to cure a hangover, even with ‘hair of the dog’.
Louis Hansel

Nicole Lee, Curtin University and Brigid Clancy, University of Newcastle

With the holiday season well underway and New Year’s Eve approaching, you might find yourself drinking more alcohol than usual.

So what actually happens to our body as we drink alcohol and wake up with a hangover?

What about memory blackouts and “hangxiety”, when you can’t remember what happened the night before or wake up with an awful feeling of anxiety?

Let’s look at what the science says – and bust some long-standing myths.

What happens when you drink alcohol?

It doesn’t matter what type of alcohol you drink – or even whether you mix drinks – the effects are basically the same with the same amount of alcohol.




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When you drink alcohol it goes into the stomach and passes into the small intestine where it’s quickly absorbed into the bloodstream.

If you have eaten something, it slows the absorption of alcohol so you don’t get drunk so quickly. That’s why it’s a good idea to eat before and during drinking.

It takes your body about an hour to metabolise 10g, or one standard drink, of alcohol.

(There are calculators that help you estimate your blood alcohol level but everybody breaks down alcohol at a different rate. So these calculators should only be used as a guide.)

What causes memory blackouts?

We all have that friend who has woken up after a big night out and not been able to remember half the night. That’s a “blackout”.

It’s different to “passing out” – you’re still conscious and able to carry out conversation, you just can’t remember it later.

The more alcohol you drink and the faster you drink it, the more likely you are to experience blackouts.

Once alcohol in your blood reaches a certain level, your brain simply stops forming new memories. If you think of your brain like a filing cabinet, files are going straight to the bin, so when you later try to look for them they are lost.

How do I sober up?

If you’ve had too much, there’s no way to sober up quickly. The only thing that can sober you up is time, so that the alcohol can be eliminated from your body.

The caffeine in coffee may make you feel more awake, but it doesn’t help break down alcohol. You will be just as intoxicated and impaired, even if you feel a little less drunk.

The same goes for cold showers, exercise, sweating it out, drinking water, and getting fresh air. These things might help you feel more alert, but they have no impact on your blood alcohol concentration or on the effects of alcohol.

What causes hangovers?

Researchers haven’t identified one single cause of hangovers, but there are a few possible culprits.

Alcohol is a diuretic, so it makes you urinate more often, which can lead to dehydration. This is especially the case if you’re in a hot, sweaty venue or dancing a lot. Dehydration can make you feel dizzy, sleepy and lethargic.

Alcohol can irritate your stomach lining, causing vomiting and diarrhoea, and electrolyte imbalance.

An imbalance of electrolytes (the minerals our body need to function properly) can make you feel tired, nauseated, and cause muscle weakness and cramps.

Hangovers can leave you tired, dehydrated, and with an irritated stomach.
Adrian Swancar/Unsplash

Too much alcohol can cause your blood vessels to dilate (expand), causing a headache. Electrolyte imbalance and dehydration can also contribute to that thumping head the next morning.

Alcohol also interferes with glucose production, resulting in low blood sugar. Not producing enough glucose can leave you feeling sluggish and weak.

Alcohol also disrupts sleep. It can make you feel sleepy at first but it interrupts the circadian cycle, sleep rhythms and REM (rapid eye movement) sleep, so later in the night you might wake up.

It can stop you from getting the quality of sleep you need to wake feeling refreshed.

Why ‘hair of the dog’ doesn’t work

There’s no way to cure a hangover, even with “hair of the dog” (having a drink the morning after). But drinking the next morning might delay the onset of symptoms, and therefore make you feel better temporarily.




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Your body needs time to rest, metabolise the alcohol you have already had, and repair any damage from a heavy night of drinking. So it’s not a good idea.

If you drink regularly and you find yourself needing a drink the next morning, this may be a sign of alcohol dependence and you should talk with your GP.

Suffering from hangxiety?

Alcohol has many effects on the brain, including that warm, relaxed feeling after a couple of drinks. But if you’ve ever felt unusually anxious after a big night out you might have experienced “hangxiety”.

Over a night of drinking, alcohol stimulates the production of a chemical in the brain called GABA, which calms the brain, and blocks the production of glutamate, a chemical associated with anxiety. This combination is why you feel cheerful and relaxed on a night out.

Your brain likes to be in balance, so in response to drinking it produces more glutamate and blocks GABA. Cue that shaky feeling of anxious dread the next morning.

What can you do if you wake up with hangxiety?

To ease some of the symptoms, try some breathing exercises, some mindfulness practices and be gentle with yourself.

There are also effective treatments for anxiety available that can help. Talk to your GP or check out some resources online.

If you’re already an anxious person, drinking alcohol may help you feel more relaxed in a social situation, but there is an even greater risk that you will feel anxiety the next day.

Prevention is better than a cure

Have a drink of water between alcoholic drinks.
Marvin Meyer/Unsplash

If you choose to drink this holiday season, the best way to avoid hangovers, hangxiety, and blackouts is to stick within recommended limits.

The new draft Australian alcohol guidelines recommend no more than ten standard drinks a week and no more than four standard drinks on any one day.

(If you want to check what a standard drink looks like, use this handy reference.)




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As well as eating to slow the absorption of alcohol, and drinking water in between alcoholic drinks to reduce the negative effects, you can also:

  • set your limits early. Decide before you start the night how much you want to drink, then stick to it

  • count your drinks and avoid shouts

  • slow down, take sips rather than gulps and avoid having shots.

If you’re worried about your own or someone else’s drinking, call the National Alcohol and other Drug Hotline on 1800 250 015 to talk through options or check out resources online.The Conversation

Nicole Lee, Professor at the National Drug Research Institute (Melbourne), Curtin University and Brigid Clancy, PhD Candidate (Psychiatry) & Research Assistant, University of Newcastle

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Can you die from a common cold?



shutterstock.
Estrada Anton/Shutterstock

Peter Barlow, Edinburgh Napier University

Most people know that the flu can kill. Indeed, the so-called Spanish flu killed 50 million people in 1918 – more than were killed in the first world war. But what about the common cold? Can you really catch your death?

The cold is a collection of symptoms – coughing, sneezing, a runny nose, tiredness and perhaps a fever – rather than a defined disease. Although it shares a lot with the initial symptoms with the flu, it’s a very different infection.

Rhinovirus causes about half of all colds, but other viruses can cause one or more of the symptoms of a cold, including adenovirus, influenza virus, respiratory syncytial virus and parainfluenza virus.

The rhinovirus causes about half of all colds.
Maryna Olyak/Shutterstock

The common cold is normally a mild illness that resolves without treatment in a few days. And because of its mild nature, most cases are self-diagnosed. However, infection with rhinovirus or one of the other viruses responsible for common cold symptoms can be serious in some people. Complications from a cold can cause serious illnesses and, yes, even death – particularly in people who have a weak immune system.

For example, studies have shown that patients who have undergone a bone marrow transplant can have a higher likelihood of developing a serious respiratory infection. While rhinovirus is not thought to be the main cause of this, other viruses that are associated with symptoms of the common cold, such as RSV, adenovirus and parainfluenza virus, are.

There is, of course, more than one way for someone to become very sick after infection with a respiratory virus. Some viruses, such as adenovirus, can also cause symptoms throughout the body, including the gastrointestinal tract, the urinary tract and the liver.

Other viruses, like the influenza virus, can themselves potentially cause severe inflammation in the lungs, but they can also lead to particularly serious conditions, such as bacterial pneumonia.




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A virus-induced bacterial infection is one way a cold or flu virus can lead to death. While the exact mechanisms of how bacterial infections can be primed by viral infection are still being investigated, a possible way it can occur is through increased bacterial attachment to cells of the lung. For example, rhinovirus has been shown to increase the presence of a receptor called PAF-r in lung cells. This can allow bacteria, such as Streptococcus pneumoniae, to bind more effectively to the cells, increasing the likelihood of it leading to a severe condition like pneumonia.

Higher risk in some people

Unfortunately, a cold can also have more severe symptoms in the very young and the very old. Older people are more likely to develop a more serious infection compared with adults or older children. And people who smoke – or who are exposed to second-hand smoke – are also more likely to get a cold and have more severe symptoms.

Another group of people who are more severely affected by infection with cold-causing viruses are people with an existing lung condition. They can include people with asthma, cystic fibrosis or chronic obstructive pulmonary disease (COPD). Infection with a virus that causes inflammation of the airways can make breathing much harder. People with COPD who catch a mild cold virus are also at risk of developing a bacterial infection.




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While the bacterial infection in these patients can be treated with antibiotics, there is no effective antiviral treatment against all types of rhinovirus. For other respiratory viruses, such as influenza, there is an effective vaccine that can help protect vulnerable people from the flu virus, including asthmatics, the very young and the very old.

There is not one single element that dictates how severe an infection with a cold virus will be, but there are many conditions or factors that can raise a red flag.




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One of the best ways to avoid catching a cold is to wash your hands properly. This can prevent the spread of many different infections, not just the viruses that cause the common cold. And everyone, not just those classed as vulnerable, should get the flu jab. For viral infections, prevention is key.The Conversation

Peter Barlow, Professor of Immunology and Infection and Head of Research of the School of Applied Sciences, Edinburgh Napier University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Feeling sick is an emotion meant to help you get better faster



The emotion of lassitude might help your body fight off infection by making certain adjustments.
Kalinka Georgieva/Shutterstock.com

Joshua Schrock, University of Oregon

You know what it’s like to be sick. You feel fatigued, maybe a little depressed, less hungry than usual, more easily nauseated and perhaps more sensitive to pain and cold.

The fact that illness comes with a distinct set of psychological and behavioral features is not a new discovery. In medical terminology, the symptom of malaise encompasses some of the feelings that come with being ill. Animal behaviorists and neuroimmunologists use the term sickness behavior to describe the observable behavior changes that occur during illness.

Health care providers often treat these symptoms as little more than annoying side effects of having an infectious disease. But as it turns out, these changes may actually be part of how you fight off infection.

I’m an anthropologist interested in how illness and infection have shaped human evolution. My colleagues and I propose that all these aspects of being sick are features of an emotion that we call “lassitude.” And it’s an important part of how human beings work to recover from illness.

Your body sets priorities when fighting germs

The human immune system is a complex set of mechanisms that help you suppress and eliminate organisms – such as bacteria, viruses and parasitic worms – that cause infection.

Activating the immune system, however, costs your body a lot of energy. This presents a series of problems that your brain and body must solve to fight against infection most effectively. Where will this extra energy come from? What should you do to avoid additional infections or injuries that would increase the immune system’s energy requirements even more?

Fever is a critical part of the immune response to some infections, but the energy cost of raising your temperature is particularly high. Is there anything you can do to reduce this cost?

To eat or not to eat is a choice that affects your body’s fight against infection. On one hand, food ultimately provides energy to your body, and some foods even contain compounds that may help eliminate pathogens. But it also takes energy to digest food, which diverts resources from your all-out immune effort. Consuming food also increases your risk of acquiring additional pathogens. So what should you eat when you’re sick, and how much?

We humans are highly dependent on others to care for and support us when we’re sick. What should you do to make sure your friends and family care for you when you’re ill?

My colleagues and I propose that the distinctive changes that occur when you get sick help you solve these problems automatically.

  • Fatigue reduces your level of physical activity, which leaves more energy available for the immune system.
  • Increased susceptibility to nausea and pain makes you less likely to acquire an infection or injury that would further increase the immune system’s workload.
  • Increased sensitivity to cold motivates you to seek out things like warm clothing and heat sources that reduce the costs of keeping body temperature up.
  • Changes in appetite and food preferences push you to eat (or not eat) in a way that supports the fight against infection.
  • Feelings of sadness, depression and general wretchedness provide an honest signal to your friends and family that you need help.

Of course these changes depend on the context. Any parents reading this article are likely familiar with the experience of being sick but pushing through it because a child needs care. While it may make sense to reduce food intake to prioritize immunity when the sick individual has plenty of energy reserves, it would be counterproductive to avoid eating if the sick person is on the verge of starvation.

Your body needs you to do (or avoid) a few things so it can concentrate on getting better.
tommaso79/Shutterstock.com

Sickness as an emotion

So how does your body organize these advantageous responses to infection?

The evidence my colleagues and I reviewed suggests that humans possess a regulatory program that lies in wait, scanning for indicators that infectious disease is present. When it detects signs of infection, the program sends a signal to various functional mechanisms in the brain and body. They in turn change their patterns of operation in ways that are useful for fighting infection. These changes, in combination with each other, produce the distinct experience of being sick.

This kind of coordinating program is what some psychologists call an emotion: an evolved computational program that detects indicators of a specific recurrent situation. When the certain situation arises, the emotion orchestrates relevant behavioral and physiological mechanisms that help address the problems at hand.

Imagine you’re walking through the woods, thinking you’re alone, and suddenly you are startled by sounds suggesting a large animal is in the underbrush nearby. Your pupils dilate, your hearing becomes attuned to every little sound, your cardiovascular system starts to work harder in preparation for either running away or defending yourself. These coordinated physiological and behavioral changes are produced by an underlying emotion program that corresponds to what you might think of as a certain kind of fear.

Some of these coordinating programs line up nicely with general intuitions about what makes up an emotion. Others have functions and features that we might not typically think of as “emotional.”

Some psychologists suggest these emotion programs likely evolved to respond to identifiable situations that occurred reliably over evolutionary time, that would affect the survival or reproduction of those involved.

This way of thinking has helped researchers understand why some emotions exist and how they work. For instance, the pathogen disgust program detects indicators that some potentially infectious agent is nearby. Imagine you smell the stench of feces: The emotion of disgust coordinates your behavior and physiology in ways that help you avoid the risky entity.

Another example is the emotion of shame, which scouts for signs that you’ve done something that causes members of your social group to devalue you. When you detect one of these indicators – a loved one rebukes you for doing something that hurt them, say – the experience of shame helps you adjust your mental map of what kinds of things will cause others to devalue you. Presumably you will try to avoid them in the future.

Drawing from the emerging discipline of evolutionary medicine, my colleagues and I now apply the idea of these emotion programs to the experience of being sick. We call this emotion “lassitude” to distinguish the underlying program from the outputs it generates, such as sickness behavior and malaise.

We hope that our approach to lassitude will help solve problems of practical importance. From a medical perspective, it would be useful to know when lassitude is doing its job and when it is malfunctioning. Health care providers would then have a better sense of when they ought intervene to block certain parts of lassitude and when they should let them be.

[ Deep knowledge, daily. Sign up for The Conversation’s newsletter. ]The Conversation

Joshua Schrock, Ph.D. Candidate in Anthropology, University of Oregon

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Hangovers: this is what happens to your body when you’ve had one too many



Elur/Shutterstock

Hal Sosabowski, University of Brighton

Having a few drinks at Christmas is, for some people, as much a part of the festive tradition as presents, decorations or carols. So if you find yourself nursing a hangover on Boxing Day, you might be interested to know what’s actually going on inside your body and why you feel so bad.

We tend to drink because in low doses alcohol is initially a euphoriant, it makes you feel happier. It does this by causing the body to release dopamine and endorphins, chemicals that stimulate the brain’s reward system. But, after a while and as you drink more, it ultimately suppresses some brain activity and slows down your heart and breathing.

The effects of the initial intake of any alcohol is the first of many stages of narcosis, the last of which is death. There just happens to be a large window between an effective dose (which has you thinking you are far more witty and handsome than you actually are and, later, running down the street with a traffic cone on your head) and a lethal dose (which has you on a mortuary slab).




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Note that even before you arrive at the typical drink drive limit, you might experience excitement, uncoordination, impairment, speech slurring, swaying and loss of inhibition. And yet you’ll still legally be able to drive a car. Small amounts of alcohol affect the limbic system in the brain, which result in aggression and the Friday and Saturday night melees common in many town centres.

Alcohol is also a vasodilator, which means it widens blood vessels, diverting blood from the body’s core to its extremities. This results in the characteristic flushed cheeks you can get from consuming alcohol and also the red nose often sported by dyed-in-the-wool drinkers.

What could possibly go wrong?
Wave break media/Shutterstock

Initially, drinking alcohol is self-reinforcing. What might seem a good idea initially seems an even better idea after you’ve had a few. Alcohol is absorbed quicker than most things since some is absorbed in the stomach (rather than the small intestine). It then spreads throughout the body and is distributed to all organs including the brain and the liver, where the body makes a valiant attempt to break down and dispose of the alcohol.

To do this, the liver produces enzymes, small molecules that help either make or break down important molecules. In this case, the enzyme alcohol dehydrogenase breaks down the alcohol (ethanol) into acetaldehyde (ethanal), which is then further broken down into acetic (ethanoic) acid and then to carbon dioxide.

Energy is also released at all stages of the breakdown, which explains why heavy drinkers can sometimes be overweight. In fact, long-term alcoholics often get most of their calories from alcohol and eat very little. This can make them overweight but curiously undernourished because they are consuming empty calories and no vitamins or protein, which can produce a general appearance and feeling of illness.

Why you vomit

The first stage breakdown product, ethanal, is an emetic, which means it makes you want to vomit. As you drink and become more euphoric, your blood ethanol level is being monitored by the area postrema, the part of your brain which checks your blood for things that shouldn’t be there. If you eat some food which causes vomiting and diarrhoea, it’s your postrema that has instructed your body to get rid of the offending comestibles.

Ethanal has the same effect. The postrema works to very fine tolerances, and as soon as your body contains enough ethanal, and the threshold that nature has set is reached, the postrema instructs your stomach to contract and makes you sick. Trying to stop this is like trying to hold back the tide. You may have noticed the very short time between drinking enthusiastically and realising that it’s a question of when, and not if, you are going to vomit.

Disulfiram (Antabuse) is a drug used to treat chronic alcoholism that stops the subsequent breakdown of ethanal after you drink, causing an immediate hangover and explosive vomiting. It’s effectively a form of aversion therapy.

Hangover causes

Unfortunately, there’s no drug to treat drunkenness itself – or a hangover. Once you are intoxicated you just have to wait it out. The liver can metabolise between 8g and 12g of alcohol in an hour and the only way to become less drunk is to stop drinking so the alcohol can diffuse out of your brain and your liver can complete the breakdown.

Aside from the vomiting, we don’t know exactly why we feel so terrible when we’re hungover, but it is thought to be another effect of ethanal and congeners, the non-alcoholic chemical clutter that is a by-product of fermentation. These include oils, minerals and other forms of alcohol such as methanol (wood alcohol), which can cause you to go blind in high doses.




Read more:
Lining your stomach with milk before a big night out – and other alcohol myths


Darker drinks have higher amounts of congeners. Red wine also causes a particularly vicious hangover since it contains a vasoconstrictor, which constricts your blood vessels and causes that throbbing headache. Meanwhile, vodka might be more forgiving since “pure” vodka is just alcohol and water.

The only other thing that might help reduce your hangover after a heavy drinking session is a glass of water before bed. Alcohol stops your pituitary gland producing the anti-diuretic hormone vasopressin, which normally restricts urine production. This means you end up losing more water than you take in, causing dehydration that irritates the blood vessels, leading to headaches.

Otherwise, you’ll just have to console your post-Christmas blues with roast dinner leftovers and your favourite holiday film.The Conversation

Hal Sosabowski, Professor of Public Understanding of Science, University of Brighton

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Should you avoid meat for good health? How to slice off the facts from the fiction



Meat is a very popular food for most Americans. Its nutritional value is a topic of much debate.
puhhha/Shutterstock.com

Dariush Mozaffarian, Tufts University

More than half of Americans who make New Year’s resolutions resolve to “eat healthier.” If you’re one, you might be confused about the role meat should play in your health.

It’s no wonder you’re confused. One group of scientists says that reducing red and processed meat is a top priority for your health and the planet’s. Another says these foods pose no problems for health. Some of your friends may say it depends, and that grass-fed beef and “nitrite-free” processed meats are fine. At the same time, plant-based meat alternatives are surging in popularity, but with uncertain health effects.

As a cardiologist and professor of nutrition, I’d like to clear up some of the confusion with five myths and five facts about meat.

First, the myths.

Red meat, while very popular, has not been shown to have health benefits.
Natalia Lisovskaya/Shutterstock.com

Myth: Red meat is good for health

Long-term observational studies of heart disease, cancers or death and controlled trials of risk factors like blood cholesterol, glucose and inflammation suggest that modest intake of unprocessed red meat is relatively neutral for health. But, no major studies suggest that eating it provides benefits.

So, while an occasional serving of steak, lamb or pork may not worsen your health, it also won’t improve it. And, too much heme iron, which gives red meat its color, may explain why red meat increases risk of Type 2 diabetes. Eating red meat often, and eating processed meat even occasionally, is also strongly linked to colorectal cancer.

Myth: You should prioritize lean meats

For decades, dietary guidance has focused on lean meats because of their lower fat, saturated fat and cholesterol contents. But these nutrients don’t have strong associations with heart attacks, cancers or other major health outcomes.

Other factors appear more important. Processed meats, such as bacon, sausage, salami and cold cuts, contain high levels of preservatives. Sodium, for example, raises blood pressure and stroke risk, while the body converts nitrites to cancer-causing nitrosamines. Lean or not, these products aren’t healthy.

Myth: Focus on a ‘plant-based’ diet

“Plant-based” has quickly, but somewhat misleadingly, become a shorthand for “healthy.” First, not all animal-based foods are bad. Poultry and eggs appear relatively neutral. Dairy may have metabolic benefits, especially for reducing body fat and Type 2 diabetes. And, seafood is linked to several health benefits.

Conversely, many of the worst foods are plant-based. Consider white rice, white bread, fries, refined breakfast cereals, cookies and so on. These foods are high in refined starch and sugar, representing 42% of all calories in the U.S., compared to about 5% of U.S. calories from unprocessed red meats, and 3% from processed meats.

Either a “plant-based” or omnivore diet is not healthy by default. It depends on what you choose to eat.

Myth: Grass-fed beef is better for your health

Conventional livestock eat a combination of forage (grass, other greens, legumes) plus hay with added corn, soy, barley or grain. “Grass-fed,” or “pasture-raised,” livestock eat primarily, but not exclusively, forage. “Grass-finished” livestock should, in theory, only eat forage. But no agency regulates industry’s use of these terms. And “free range” describes where an animal lives, not what it eats.

“Grass-fed” may sound better, but no studies have compared health effects of eating grass-fed versus conventional beef. Nutrient analyses show very modest differences between grass-fed and conventionally raised livestock. You might eat grass-fed beef for personal, environmental or philosophical reasons. But don’t expect health benefits.

Myth: Plant-based meat alternatives are healthier

Products like Impossible Burger and Beyond Meat are clearly better for the environment than conventionally raised beef, but their health effects remain uncertain. Most nutrients in plant-based alternatives are, by design, similar to meat. Using genetically engineered yeast, Impossible even adds heme iron. These products also pack a lot of salt. And, like many other ultra-processed foods, they may lead to higher calorie intake and weight gain.

So, what are the facts?

Sausages wrapped in bacon are a double whammy of unhealthy meat, as both bacon and sausage are processed meats.
MShev/Shutterstock.com

Fact: Processed meats are bad for health

Processed meats contain problematic preservatives. Even those labeled “no nitrates or nitrites added” contain nitrite-rich fermented celery powder. A current petition by the Center for Science in the Public Interest asks the FDA to ban the misleading labeling.

Besides the sodium, nitrites and heme, processed meats can contain other carcinogens, produced by charring, smoking or high-temperature frying or grilling. These compounds may not only harm the person who eats these products; they can also cross the placenta and harm a fetus.

Fact: A meatless diet is not, by itself, a healthy diet

Most diet-related diseases are caused by too few health-promoting foods like fruits, nuts, seeds, beans, vegetables, whole grains, plant oils, seafood and yogurt. Additional health problems come from too much soda and ultra-processed foods high in salt, refined starch or added sugar. Compared to these major factors, avoiding or occasionally eating unprocessed red meat, by itself, has modest health implications.

Fact: Beef production is devastating the environment

In terms of land use, water use, water pollution and greenhouse gases, unprocessed red meat production causes about five times the environmental impact of fish, dairy or poultry. This impact is about 20 times higher than that of eggs, nuts or legumes, and 45 to 75 times higher than the impact of fruits, vegetables or whole grains. A 2013 UN report concluded that livestock production creates about 15% of all global greenhouse gas emissions, with nearly half coming from beef alone.

Fact: Plant-based meats are better for the environment

Production of plant-based meat alternatives, compared to conventional beef, uses half the energy, one-tenth of the land and water, and produces 90% less greenhouse gas. But, no studies have yet compared plant-based meat alternatives to more natural, less processed options, such as mushrooms or tofu.

Fact: Many questions remain

Which preservatives or other toxins in processed meat cause the most harm? Can we eliminate them? In unprocessed red meats, what exactly increases risk of Type 2 diabetes? What innovations, like feeding cows special strains of seaweed or using regenerative grazing, can reduce the large environmental impacts of meat, even grass-fed beef? What are the health implications of grass-fed beef and plant-based meat alternatives?

Like much in science, the truth about meat is nuanced. Current evidence suggests that people shouldn’t eat unprocessed red meat more than once or twice a week. Grass-fed beef may be modestly better for the environment than traditional production, but environmental harms are still large. Data don’t support major health differences between grass fed and conventional beef.

Similarly, plant-based meat alternatives are better for the planet but not necessarily for our health. Fruits, nuts, beans, vegetables, plant oils and whole grains are still the best bet for both human and planetary health.

[ You’re smart and curious about the world. So are The Conversation’s authors and editors. You can read us daily by subscribing to our newsletter. ]The Conversation

Dariush Mozaffarian, Dean of Nutrition Science and Policy, Tufts University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Hangovers happen as your body tries to protect itself from alcohol’s toxic effects



A night of revelry can mean an uncomfortable day after.
Everett Collection/Shutterstock.com

Daryl Davies, University of Southern California; Joshua Silva, University of Southern California, and Terry David Church, University of Southern California

Debaucherous evening last night? You’re probably dealing with veisalgia right now.

More commonly known as a hangover, this unpleasant phenomenon has been dogging humanity since our ancestors first happened upon fermentation.

Those nasty vertigo-inducing, cold sweat-promoting and vomit-producing sensations after a raucous night out are all part of your body’s attempt to protect itself from injury after you overindulge in alcoholic beverages. Your liver is working to break down the alcohol you consumed so your kidneys can clear it out ASAP. But in the process, your body’s inflammatory and metabolic reactions are going to lay you low with a hangover.

As long as people have suffered from hangovers, they’ve searched in vain for a cure. Revelers have access to a variety of compounds, products and devices that purport to ease the pain. But there’s a lot of purporting and not a lot of proof. Most have not been backed up well by science in terms of usefulness for hangover treatment, and often their effects don’t seem like they’d match up with what scientists know about the biology of the hangover.

Drain enough cups of booze in one session and you know what’s bound to follow.
Laura buron/Unsplash, CC BY-ND

Working overtime to clear out the booze

Hangovers are virtually guaranteed when you drink too much. That amount varies from person to person based on genetic factors as well as whether there are other compounds that formed along with ethanol in the fermentation process.

Over the course of a night of heavy drinking, your blood alcohol level continues to rise. Your body labors to break down the alcohol – consumed as ethanol in beer, wine or spirits – forming damaging oxygen free radicals and acetaldehyde, itself a harmful compound. The longer ethanol and acetaldehyde stick around, the more damage they can do to your cellular membranes, proteins and DNA, so your body’s enzymes work quickly to metabolize acetaldehyde to a less toxic compound, acetate.

Over time, your ethanol levels drop through this natural metabolic process. Depending on how much you consumed, you’re likely to experience a hangover as the level of ethanol in your blood slowly returns to zero. Your body is withdrawing from high levels of circulating alcohol, while at the same time trying to protect itself from the effects of alcohol.

Scientists have limited knowledge of the leading causes of the hangover. But they do know that the body’s responses include changes in hormone levels to reduce dehydration and cellular stress. Alcohol consumption also affects a variety of neurotransmitter systems in the brain, including glutamate, dopamine and serotonin. Inflammation increases in the body’s tissues, and the healthy gut bacteria in your digestive system take a hit too, promoting leaky gut.

Altogether, the combination of all these reactions and protective mechanisms activated by your system gives rise to the experience of a hangover, which can last up to 48 hours.

Your misery likely has company

Drinking and socializing are cultural acts, and most hangovers do not happen in isolation. Human beings are social creatures, and there’s a high likelihood that at least one other individual feels the same as you the morning after the night before.

Each society has different rules regarding alcohol use, which can affect how people view alcohol consumption within those cultures. Drinking is often valued for its relaxing effect and for promoting sociability. So it’s common to see alcohol provided at celebratory events, social gatherings and holiday parties.

For many people, ‘partying’ is synonymous with ‘drinking.’
Lidya Nada/Unsplash, CC BY-ND

In the United States, drinking alcohol is largely embraced by mainstream culture, which may even promote behaviors involving excessive drinking. It should be no surprise that overindulgence goes hand in hand with these celebratory social events – and leads to hangover regrets a few hours later.

Your body’s reactions to high alcohol intake and the sobering-up period can influence mood, too. The combination of fatigue that you experience from sleep deprivation and hormonal stress reactions, in turn, affect your neurobiological responses and behavior. As your body is attempting to repair itself, you’re more likely to be easily irritated, exhausted and want nothing more than to be left alone. Of course, your work productivity takes a dramatic hit the day after an evening of heavy drinking.

When all is said and done, you’re the cause of your own hangover pain, and you’re the one who must pay for all the fun of the night before. But in short order, you’ll forget how excruciating your last hangover was. And you may very soon talk yourself into doing the things you swore you’d never do again.

Speeding up recovery

While pharmacologists like us understand a bit about how hangovers work, we still lack a true remedy.

Countless articles describe a variety of foods, caffeine, ion replenishment, energy drinks, herbal supplements including thyme and ginger, vitamins and the “hair of the dog” as ways to prevent and treat hangovers. But the evidence isn’t really there that any of these work effectively. They’re just not scientifically validated or well reproduced.

For example, Kudzu root (Pueraria lobata), a popular choice for hangover remedies, has primarily been investigated for its effects in reducing alcohol-mediated stress and hangover. But at the same time, Kudzu root appears to inhibit the enzymes that break down acetaldehyde – not good news since you want to clear that acetaldehyde from your system quickly.

To fill this knowledge gap, our lab is working with colleagues to see if we can find scientific evidence for or against potential hangover remedies. We’ve focused on the benefits of dihydromyricetin, a Chinese herbal medicine that is currently available and formulated as a dietary supplement for hangover reduction or prevention.

Dihydromyricetin appears to work its magic by enhancing alcohol metabolism and reducing its toxic byproduct, acetaldehyde. From our findings in mice models, we are collecting data that support the usefulness of dihydromyricetin in increasing the expression and activity of enzymes responsible for ethanol and acetaldehyde metabolism in the liver, where ethanol is primarily broken down. These findings explain one of the several ways dihydromyricetin protects the body against alcohol stress and hangover symptoms.

We are also studying how this enhancement of alcohol metabolism results in changes in alcohol drinking behaviors. Previously, dihydromyricetin was found to counteract the relaxation affect of drinking alcohol by interfering with particular neuroreceptors in the brain; rodents didn’t become as intoxicated and consequently reduced their ethanol intake. Through this combination of mechanisms, we hope to illustrate how DHM might reduce the downsides of excessive drinking beyond the temporary hangover, and potentially reduce drinking behavior and damage associated with heavy alcohol consumption.

Of course, limiting alcohol intake and substituting water for many of those drinks during an evening out is probably the best method to avoid a painful hangover. However, for those times when one alcoholic beverage leads to more than a few more, be sure to stay hydrated and catch up on rest. Your best bet for a smoother recovery is probably some combination of nonsteroidal anti-inflammatory drug like ibuprofen, Netflix and a little downtime.

[ Deep knowledge, daily. Sign up for The Conversation’s newsletter. ]The Conversation

Daryl Davies, Professor of Clinical Pharmacy, University of Southern California; Joshua Silva, Ph.D. Candidate in Clinical and Experimental Therapeutics, University of Southern California, and Terry David Church, Assistant Professor of Regulatory and Quality Sciences, University of Southern California

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How to pick the right sunscreen when you’re blinded by choice



We’re spoilt for choice when it comes to sunscreen in Australia. So how do you choose the right one?
from www.shutterstock.com

Katie Lee, The University of Queensland and Erin McMeniman, The University of Queensland

There’s an enourmous variety of sunscreens to choose from. Major supermarkets each sell more than 60 options. And one large pharmacy chain sells more than 100.

So how do you choose sunscreen that’s right for you?




Read more:
Inducing choice paralysis: how retailers bury customers in an avalanche of options


The big 4 must haves

Sunscreens need to tick these four major boxes:

  1. The sun protection factor, or SPF, should be at least 30, preferably 50. SPF describes how much UV gets to the skin. SPF50 allows just 1/50th (2%) of the UV to reach the skin

  2. Go for broad spectrum protection, which filters the full UV light spectrum. UVB rays (290-320nm wavelengths) are responsible for most sunburn and DNA damage, but UVA rays (320-400nm) also cause DNA damage and accelerate skin ageing

  3. Aim for water resistant formulations, which stay on longer in sweaty conditions, and when exercising or swimming. But no sunscreen is completely waterproof

  4. Make sure the sunscreen is approved in Australia. Approval from the Therapeutic Goods Administration (TGA) is the final must-have. All sunscreens for sale in Australia must meet the TGA’s requirements and will carry an AUST number on the packaging. They can only contain ingredients from an approved list that have been tested for safety and efficacy. And the SPF, water resistance and broad spectrum action must be established by testing on human skin. Sunscreens bought overseas don’t necessarily have these safeguards, so proceed with caution.

Once you’ve ticked off the big four, you can limit your options by how the sunscreen is delivered, its ingredients, and other factors.

Pump pack, roll-on or spray?

The sunscreen delivery system is more important than you might think. Sunscreen works best when you use lots — a teaspoon for each limb, a teaspoon each for your front and back, and a teaspoon for your face and neck.

This is easiest to achieve with pump packs or squeeze tubes. People apply far less sunscreen when they use a roll-on. Spray-on sunscreen is even worse; the TGA recommends you apply one-third of a whole can for proper coverage.

How to use sunscreen (Cancer Council)

Look and feel, sensitive skin and kids

Now we get down to the finer choices in sunscreen, and they depend on your personal concerns and preferences. Here are a few common choices.

How to avoiding looking greasy

Greasiness is the most off-putting thing about sunscreen for many Australians.

But there are non-greasy formulations, often marketed as “dry-touch” or “matte finish”. These can be comparatively expensive, but worth it if greasiness is your main barrier to using sunscreen.

Your skin may still look shiny immediately after applying it. But it should return to a matte finish within 10-20 minutes as the sunscreen settles into the epidermis, the outer layer of the skin.

How about sunscreen for sensitive or acne-prone skin?

Sensitive skin is irritated by a wide variety of cosmetics, lotions and fragrances. So, you can use ones marketed as kids’ sunscreen because these tend to be fragrance-free.

You can also choose sunscreens with ingredients such as zinc oxide or titanium dioxide, which partially reflect and also absorb UV rays.

Those so-called physical blockers are very unlikely to cause allergic or irritant rashes. But they appear white on the skin, unless you chose an option with nano-sized particles, which are invisible to the eye.

Sunscreens containing zinc oxide or titanium oxide are unlikely to inflame sensitive skin.
from www.shutterstock.com

If your skin is prone to acne, good options are lotions or gels, rather than creams, and products marked oil-free or non-comedogenic.

Sensitive and acne-prone skin is often limited to the face and neck, so it can be cheaper to have a specialist sunscreen for those parts and a cheaper one for the rest of your body.

Sunscreen allergies are rarer but do affect up to 3% of people. They’re generally caused by a single sunscreen component, usually preservatives or fragrances. A dermatologist can patch test individual ingredients, which you can then avoid by checking labels.

What’s the best sunscreen for my kids?

Parents worry about the effects of both UV exposure and chemical exposure. And of course, small children can be pretty anti-sunscreen.

All Australian sunscreen chemicals are approved by the TGA and are recommended for daily use, even on kids. Plus, many kids’ sunscreens are made with sensitive skin in mind, because skin sensitivity is more common in young children. If your child doesn’t have sensitive skin (skin that reacts with itching or burning sensations to a wide range of body care products), adult sunscreens are fine too.

However, babies under six months old need a physical blocker sunscreen.

What not to do

The Cancer Council and the TGA strongly recommend against homemade sunscreens.

Natural oils and other ingredients promoted in recipes found online generally have a low SPF. And, as they have not been tested for causing irritation, can react unpredictably with the skin.

Cosmetics that contain sunscreen, such as lipstick or foundation with an SPF rating, are not regulated as tightly as regular sunscreens in Australia.

Cosmetics with an SPF 30 or higher can have good protection when you first apply them. But like regular sunscreens, they need to be reapplied throughout the day. That’s not something we usually do, unless you’re going for the caked-on look.




Read more:
Explainer: what happens to your skin when you get sunburnt?


The Conversation


Katie Lee, Research assistant, The University of Queensland and Erin McMeniman, Senior Lecturer Princess Alexandra Hospital Southside Clinical Unit and Casual Research Assistant, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Why is my poo green?



Strange coloured poo is usually due to the food we’ve eaten, medication we’ve taken, or the processes involved in breaking down what we ingest.
Nomad_Soul/Shutterstock

Vincent Ho, Western Sydney University

It’s happened to many of us at some point in our lives: we finish our bowel movement, look down in the bowl and have a moment of panic when we see an unusual colour.

Poo can be found in many colours other than brown, with green poo often eliciting concern. But it’s surprisingly common and is usually no reason to be alarmed.




Read more:
Do we have to poo every day? We asked five experts


Why poo is usually brown

The brown colour of poo initially comes from the red of blood. Haemoglobin is the red protein in blood that transports oxygen around the body. It’s eventually broken down into a substance called bilirubin.

In the liver, bilirubin is used to form bile and is released into the small bowel to help digest food. Bile then passes into the colon and the bilirubin is broken down by bacteria.

The final stage in the process is the addition of a substance called stercobilin, which gives poo its brown colour.

All shades of brown are considered normal.

Green poo in adults

Stool colour is very heavily influenced by the substances in the gut that digest food and what you eat.

Green stools contain significantly more bile acids than brown stools. If food is moving through the bowel very quickly – if you have diarrhoea, for instance – there isn’t enough time for the green bile to break down completely, giving stools a green colour.

Green leafy vegetables such as spinach and lettuce contain large amounts of chlorophyll (green pigment) bound to magnesium. This can lead to stools turning green.

Sometimes it comes down to what you ate.
Natali Zakharova/Shutterstock

Some green food dyes such as natural green 3 contain chlorophyll (green pigment) bound to copper which can turn stools a dark green.

Why do babies have green poo?

A newborn’s first stool, called meconium, is very often dark green.

Green stools in formula-fed infants are often due to formulas containing high amounts of iron.

But even for breastfed infants it’s normal to have yellow-green or green poo.

In fact, it’s normal for babies’ poo to be many different colours. One study found pale stools were caused by partially digested milk fats, yellow stools were due to stercobilin (which is also involved in making poo brown) and other similar compounds, and dark stools due to bilirubin or the presence of meconium.

What about other colours of poo?

Blue

Some food dyes, food additives and naturally occurring colours are unable to be completely broken down in the gut and this can distinctly colour poo. Children who have consumed a lot of blue-coloured drinks, for instance, often poo blue.




Read more:
Curious Kids: how does my tummy turn food into poo?


Blueberries can also turn poo blue because of a type of antioxidant called anthrocyanin. Most anthrocyanins in blue berries are broken down by the time they reach the colon, so kids with blue poo will either have consumed quite a lot or the berries are moving quickly through the gut.

Children with diarrhoea have a very rapid gut transit and stools often come out the same colour as the food that went in.

Eating lots of blueberries can turn poo blue.
Kaspars Grinvalds/Shutterstock

Orange

Orange stools can be due to beta carotene, a compound found in particular vegetables such as carrots and butternut pumpkin.

Poo can also be orange because of the effects of antacids containing aluminium hydroxide, a naturally occurring salt.

Yellow

Yellow-coloured poo is often normal but a greasy, foul-smelling yellow stool that floats on the toilet water can mean it contains an excess of fat.

Occasionally, this can arise from conditions such as undiagnosed coeliac disease, where the immune system reacts abnormally to gluten and the small bowel doesn’t properly absorb fat.

Pale, cream or clay-cloured

Abnormally pale or clay-coloured stools can indicate a blockage of bile from the liver to the small intestine. This means it doesn’t go through the last stage of getting its brown colour, through the addition of stercobilin. This results in poo having a very distinct pale cream appearance.

One in 14,000 Australian babies are born with a condition called biliary atresia, where the bile ducts outside and inside the liver are scarred and blocked. Bile is unable to flow out of the liver, which can lead to liver scarring. Biliary atresia can be treated with surgery but early diagnosis is important.

Pale coloured poo may also indicate the presence of an intestinal parasite or bacteria.

Red

Red poo could be due to red food colouring, tomato juice and beetroot.

Last night’s beetroot salad could be to blame.
Gayvoronskaya_Yana/Shtterstock

However, bright red blood in the poo usually means internal bleeding from the bowel.

Causes of red blood in the poo can include conditions such as haemorrhoids and anal fissures (small, thin tears) but may be the sign of a more sinister bowel cancer.




Read more:
Your poo is (mostly) alive. Here’s what’s in it


Black

There can be a number of harmless causes for black poo such as eating black licorice.

Medications are another reason. Iron tablets and many antibiotics can turn poo black. (Antibiotics are also known to turn poo into different shades of green, white, pink and orange.)

Black, tar-like poo can indicate bleeding from higher up in the digestive tract, such as from an oesophageal or stomach ulcer.

Should you be worried?

Changes to the colour of your poo are usually temporary. Getting rid of the culprit – by finishing the medication or removing the responsible food from the diet, for instance – should be able to return poo colour to its normal shade of brown.

If the odd colour persists, it may signify an underlying medical condition and warrant further investigation.

Black, red and very pale poo are the more concerning colours and should be checked out by your GP.The Conversation

Vincent Ho, Senior Lecturer and clinical academic gastroenterologist, Western Sydney University

This article is republished from The Conversation under a Creative Commons license. Read the original article.