Evidence gathered over 60 years about adding fluoride to drinking water has failed to convince some people this major public health initiative is not only safe but helps to prevent tooth decay.
Myths about fluoridated water persist. These include fluoride isn’t natural, adding it to our water supplies doesn’t prevent tooth decay and it causes conditions ranging from cancer to Down syndrome.
Now the National Health and Medical Research Council (NHMRC) is in the process of updating its evidence on the impact of fluoridated water on human health since it last issued a statement on the topic in 2007.
Its draft findings and recommendations are clear cut:
NHMRC strongly recommends community water fluoridation as a safe, effective and ethical way to help reduce tooth decay across the population.
Here are four common myths the evidence says are wrong.
Fluoride is a naturally occurring substance found in rocks that leaches into groundwater; it’s also found in surface water. The natural level of fluoride in the water varies depending on the type of water (groundwater or surface) and the type of rocks and minerals it’s in contact with.
There are many places in Australia where fluoride occurs naturally in the water supply at optimum levels to maintain good dental health. For example, both Portland and Port Fairy in Victoria have naturally occurring fluoride in their water at 0.7-1.0 parts per million.
The type of fluoride commonly found in many rocks and the source of the naturally occurring fluoride ion in water supplies is calcium fluoride.
The three main fluoride compounds generally used to fluoridate water are: sodium fluoride, hydrofluorosilicic acid (hexafluorosilicic acid) and sodium silicofluoride. All these fully mix (dissociate) in water, resulting in the availability of fluoride ions to prevent tooth decay.
So regardless of the original compound source, the end result is the same – fluoride ions in the water.
Evidence for water fluoridation dates back to US studies in the 1940s, where dental researchers noticed lower levels of tooth decay in areas with naturally occurring fluoride in the water supply.
This prompted a study involving the artificial fluoridation of water supplies to a large community, and comparing the tooth decay rates to a neighbouring community with no fluoride.
The trial had to be discontinued after six years because the benefits to the children in the fluoridated community were so obvious it was deemed unethical to not provide the benefits to all the children, and so the control community water supply was also fluoridated.
Further reading: How fluoride in water helps prevent tooth decay
Since then, consistently we see lower levels of tooth decay associated with water fluoridation, and the most recent evidence, from Australia and overseas, supports this.
The NHMRC review found children and teenagers who had lived in areas with water fluoridation had 26-44% fewer teeth or surfaces affected by decay, and adults had 27% less tooth decay.
A number of factors are likely to influence the variation across populations and countries, including diet, access to dental care, and the amount of tap water people drink.
The NHMRC found, there was reliable evidence to suggest water fluoridation at current levels in Australia of 0.6-1.1 parts per million is not associated with: cancer, Down syndrome, cognitive problems, lowered intelligence, hip fracture, chronic kidney disease, kidney stones, hardening of the arteries, high blood pressure, low birth weight, premature death from any cause, musculoskeletal pain, osteoporosis, skeletal fluorosis (extra bone fluoride), thyroid problems or other self-reported complaints.
Further reading: Why do some controversies persist despite the evidence?
This confirms previous statements from the NHMRC on the safety of water fluoridation, and statements from international bodies such as the World Health Organisation, the World Dental Federation, the Australian Dental Association and the US Centers for Disease Control and Prevention.
Most studies that claim to show adverse health effects report on areas where there are high levels of fluoride occurring naturally in the water supply. This is often more than 2-10 parts per million or more, up to 10 times levels found in Australian water.
There is, however, evidence that fluoridated water is linked to both the amount and severity of dental fluorosis. This is caused by being exposed to excess fluoride (from any source) while the teeth are forming, affecting how the tooth enamel mineralises.
Most dental fluorosis in Australia is very mild or mild, and does not affect the either the function or appearance of the teeth. When you can see it, there are fine white flecks or lines on the teeth. Moderate dental fluorosis is very uncommon, and tends to include brown patches on the tooth surface. Severe dental fluorosis is rare in Australia.
Some people are concerned about using fluoridated water to make up infant formula.
However, all infant formula sold in Australia has very low levels of fluoride, below the threshold amount of 17 micrograms of fluoride/100 kilojules (before reconstitution), which would require a warning label.
Therefore, making up infant formula with fluoridated tap water at levels found in Australian (0.6-1.1 parts per million) is safe, and does not pose a risk for dental fluorosis. Indeed, Australian research shows there is no association between infant formula use and dental fluorosis.
Adding fluoride to tap water to prevent tooth decay is one of our greatest public health achievements, with evidence gathered over more than 60 years showing it works and is safe. This latest review, tailored to Australia, adds to that evidence.
Last week I had a headache. Two hours in a traffic jam, hot day, no water, plans thrown into chaos. That day I was one of the five million Australians affected by headache or migraine. Over a year one person in two will experience a headache.
Headaches are really common, so here are five things the research evidence indicates are worth trying to help manage or avoid them.
A study was conducted in people who got at least two moderately intense or more than five mild headaches a month. The participants received a stress management and sleep quality intervention with or without increasing their water intake by an extra 1.5 litres a day.
The water intervention group got a significant improvement in migraine-specific quality of life scores over the three months, with 47% reporting their headaches were much improved, compared to 25% of the control group.
However, it did not reduce the number or duration of headaches. Drinking more water is worth a try. Take a water bottle everywhere you go and refill it regularly to remind you to drink more water.
Caffeine can have opposing effects. It can help relieve some headaches due to analgesic effects but also contribute to them, due to caffeine withdrawal. A review of caffeine withdrawal studies confirmed that getting a headache was the number one symptom of withdrawal, followed by fatigue, reduced energy and alertness, drowsiness, depressed mood, difficulty concentrating, fuzzy head and others.
When people were experimentally put though controlled caffeine withdrawal, 50% got a headache, with withdrawal symptoms occurring within 12-24 hours, peaking between 20-51 hours and lasting from two to nine days. Caffeine withdrawal can happen from a usual daily dose as low as 100 mg/day. One cup of brewed coffee contains 100-150mg caffeine, instant coffee has 50-100 mg depending on how strong you make it and a cup of tea can vary from 10-90mg. It appears that maintaining usual caffeine consumption may subconsciously relate to avoidance of withdrawal symptoms.
Caffeine can dampen down pain. in a systematic review that included five headache studies with 1,503 participants with migraine or tension-type headache, 33% of participants achieved pain relief of at least 50% of the maximum possible after receiving 100 mg or more caffeine plus analgesic pain medication (ibuprofen or paracetamol) compared to 25% for the analgesic group alone.
A study in over 50,000 Norwegians, who have high caffeine intakes (more than 400 milligrams a day), examined the relationship with headaches. Those with the highest caffeine intakes (more than 540mg/day) were 10% more likely to get headaches, including migraine.
But when headache frequency was examined, high caffeine consumers were more likely to experience non-migraine headaches infrequently (less than seven per month) compared to those considered low caffeine consumers (less than 240mg a day). This was attributed to potential “reverse causation” where high caffeine consumers use caffeine to damp down headache pain. They found those with the lowest caffeine intakes (125mg a day) were more likely to report more than 14 headaches per month, which may have been due to greater sensitivity and avoidance of caffeine.
Hypnic headaches are a rare type that occurs in association with sleep. They typically last 15-180 minutes and are more common in the elderly. Hypnic headaches are treated by giving caffeine in roughly the amount found in a cup of strong coffee.
Some people get a headache after fasting for about 16 hours, which equates to not eating between 6pm and 10am the next day. A study in Denmark found one person in 25 has been affected by a fasting headache. These headaches are most likely to occur when fasting for a blood test or medical procedure or if you are following a “fasting” weight loss diet or a very low energy meal replacement diet.
Fasting headaches are likely to be confounded by caffeine withdrawal. Check the test procedure instructions to see what fluids, such as tea, coffee and water are allowed and drink within those recommendations.
In a study 34 people with new-onset migraine who kept a headache diary for about a month, those who ate a night-time snack were 40% less likely to experience a headache compared to those who didn’t snack. For susceptible individuals this may prevent fasting headaches. Try a slice or wholegrain toast with a topping like cheese and tomato or avocado and tuna, with a cuppa.
Headache is the classic feature of alcohol induced hangovers. The amount of alcohol needed to trigger a hangover varies widely between individuals, from one drink to many. A number of factors mash up to produce a throbbing post alcohol headache. Increased urination and vomiting both increase risk of dehydration which leads to changes in blood and oxygen flowing to the brain.
Congeners, a group of chemicals produced in small amounts during fermentation, give alcoholic drinks their taste, smell and colour. Metabolites of alcohol breakdown in the liver can cross the blood-brain barrier contributing to hangover.
Alcohol can trigger tension-type headaches, cluster headaches and migraine. People with migraines have been shown to have lower alcohol intakes compared to others.
The wise advice is to drink responsibly, boost your water intake and don’t drink on an empty stomach. If you are sensitive to alcohol, avoidance is your best option.
Some migraineurs are diet-sensitive. Triggers include cheese, chocolate, alcohol or other specific foods. A recent study found women with low dietary folate intakes had more frequent migraines. However a daily folic acid (1mg) supplement made no difference.
Boost your intake of foods rich in folate such as green leafy vegetables, legumes, seeds, chicken, eggs and citrus fruits. Use our Healthy Eating Quiz to check your nutrition, diet quality and variety. Keep a headache diary to identify triggers and then discuss it with your GP.
But our new study goes one step further. It predicts that higher taxes on sugar-sweetened drinks will benefit the wider economy through increased economic productivity, by having more, healthier people in paid and unpaid work.
A total of 63% Australian adults and one in four children are overweight or obese, making this both a health and an economic problem.
Obesity increases the risk of diseases including cancer, diabetes, heart disease and stroke. Obesity has also been estimated to cost Australia about A$8.6 billion a year or more. Not only does obesity drive up health-care costs, by causing illness and premature death, it also reduces people’s ability to work and contribute to the economy.
Added sugar contributes energy to the diet, but no useful nutrients. Increasingly, health experts suggest we should be treating sugar, and in particular sugar in soft drinks, as we do tobacco or alcohol, by taxing it to reduce consumption and so reduce obesity rates.
Taxing sugar is not a new concept. In the 1700s, Scottish economist Adam Smith wrote in An Inquiry into the Nature and Causes of the Wealth of Nations:
Sugar, rum, and tobacco, are commodities which are nowhere necessaries of life, which are become objects of almost universal consumption, and which are therefore extremely proper subjects of taxation.
Smith’s proposal to tax sugar was not aimed at improving health, as it is today. Now organisations like the World Health Organisation, the Australian Medical Association and many non-governmental organisations are advocating a tax on drinks with added sugar, as part of wider efforts to tackle obesity.
Until our study, few worldwide had looked at the wider economic effects of taxing sugary drinks.
We modelled the Australian adult population as it was in 2010, in terms of consumption of sugar-sweetened drinks, body mass, obesity-related diseases, death rates, and the amount of paid or unpaid work people were likely to do.
We compared a scenario in which the prices of sugared drinks went up by 20%, compared to business-as-usual, and estimated what difference this would make for the number of obese people, the number of years lived, and for overall economic production.
Further reading: Dietary guidelines don’t work. Here’s how to fix them
We used data from the 2011-12 Australian Health Survey and found that obese people aged 15-64 had a lower chance of being in a paid job, compared to people whose weight was normal. We assumed this was related to illness.
Of people in work, obese workers needed more sick leave, but only about an hour a year.
We also looked at unpaid work (like cooking, cleaning and caring, and volunteer work). We included gains due to more people surviving for longer due to lower body weight. We assumed that if work was not done as unpaid work, somebody would have to be hired to do it (so there would be a replacement cost).
Our results show that a 20% sugar tax would mean about 400,000 fewer people would be obese. Three-quarters of these would be in the workforce, so that about 300,000 fewer employed people would be obese.
Over the lifetime of the adult population of Australia in 2010, this would add about A$750 million to the formal, paid economy, due to more, healthier people producing more goods and services.
The gains in unpaid work were even larger at A$1.17 billion. Fewer obese people means more healthy people, who have a greater likelihood to do unpaid work, in the household or as volunteers.
These indirect economic benefits from increased employment in the workforce and from greater participation in unpaid work were larger than the savings in health care costs, which we estimated at about A$425 million over the lifetime of the adult population.
In all, the tax could deliver over A$2 billion in economic benefits in indirect economic benefits plus health care savings. And that does not even include the value of the gains in people’s quality of life and how long they lived.
Further reading: Fat nation: the rise and fall of obesity on the political agenda
The exact size of the benefits depend on assumptions about what people would drink (and eat) if they drink fewer sugared drinks. In this study, we used Australian evidence that found an increase only for diet drinks, which contain virtually no energy.
Other evidence finds a sugar tax reduces the consumption of sugar and energy-rich foods, but may also lead to people eating fewer fruit and vegetables and more salt. This would reduce the health benefit, and that study suggests it would be even better to tax all sugar instead of only sugared drinks.
Nevertheless, the available evidence shows health benefits of increased taxation of sugared drinks.
Studies in other countries have predicted similar effects of a sugar tax on the proportion of obese people. For example, a 20% tax is expected to reduce the number of obese people by about 1.3% in the UK and 2-4% in South Africa.
And an increasing number of countries, including the UK, France, Denmark, Finland, Hungary and recently Estonia and Saudi Arabia, have already announced or have implemented a tax on drinks with added sugar.
If Australia introduces a 20% tax on sugar-sweetened drinks, as many health advocates and economists have called for, that would not only improve health, our results predict it would also promote economic growth.
The author of this article will be available for a live Q&A today 1-2pm. Please post your questions in the comments below.
As we get older we have a greater risk of developing impairments in areas of cognitive function – such as memory, reasoning and verbal ability. We also have a greater risk of dementia, which is what we call cognitive decline that interferes with daily life. The trajectory of this cognitive decline can vary considerably from one person to the next.
Despite these varying trajectories, one thing is for sure: even cognitively normal people experience pathological changes in their brain, including degeneration and atrophy, as they age. By the time a person reaches the age of 70 to 80, these changes closely resemble those seen in the brains of people with Alzheimer’s Disease.
Even so, many people are able to function normally in the presence of significant brain damage and pathology. So why do some experience symptoms of Alzheimer’s and dementia, while others remain sharp of mind?
It comes down to something called cognitive reserve. This is a concept used to explain a person’s capacity to maintain normal cognitive function in the presence of brain pathology. To put it simply, some people have better cognitive reserve than others.
Evidence shows the extent of someone’s cognitive decline doesn’t occur in line with the amount of biological damage in their brain as it ages. Rather, certain life experiences determine someone’s cognitive reserve and, therefore, their ability to avoid dementia or memory loss.
Being educated, having higher levels of social interaction or working in cognitively demanding occupations (managerial or professional roles, for instance) increases resilience to cognitive decline and dementia. Many studies have shown this. These studies followed people over a number of years and looked for signs of them developing cognitive decline or dementia in that period.
Cognitive reserve is traditionally measured and quantified based on self reports of life experience such as education level, occupational complexity and social engagement. While these measures provide an indication of reserve, they’re only of limited use if we want to identify those at risk of cognitive decline. Genetic influences obviously play a part in our brain development and will influence resilience.
The fundamental brain mechanisms that underpin cognitive reserve are still unclear.
The brain consists of complex, richly interconnected networks that are responsible for our cognitive ability. These networks have the capacity to change and adapt to task demands or brain damage. And this capacity is essential not only for normal brain function, but also for maintaining cognitive performance in later life.
This adaptation is governed by brain plasticity. This is the brain’s ability to continuously modulate its structure and function throughout life in response to different experiences. So, plasticity and flexibility in brain networks likely contribute in a major way to cognitive reserve and these processes are influenced by both genetic profiles and life experiences.
A major focus of our research is examining how brain connectivity and plasticity relate to reserve and cognitive function. We hope this will help identify a measure of reserve that reliably identifies individuals at risk of cognitive decline.
While there is little we can do about our genetic profile, adapting our lifestyles to include certain types of behaviours offers a significant opportunity to improve our cognitive reserve.
Activities that engage your brain, such as learning a new language and completing crosswords, as well as having high levels of social interaction, increase reserve and can reduce your risk of developing dementia.
Regular physical activity also improves cognitive function and reduces the risk of dementia. Unfortunately, little evidence is available to suggest what type of physical activity, as well as intensity and amount, is required to best increase reserve and protect against cognitive impairment.
There is also mounting evidence that being sedentary for long periods of the day is bad for health. This might even undo any benefits gained from periods of physical activity. So, it is important to understand how the composition of physical activity across the day impacts brain health and reserve, and this is an aim of our work.
Our ongoing studies should contribute to the development of evidence-based guidelines that provide clear advice on physical activity patterns for optimising brain health and resilience.
If you have a blocked or runny nose, chances are you’ll reach for a tissue or hanky to clear the mucus by having a good blow.
But is there a right way to blow your nose? Could some ways make your cold worse? And could you actually do some damage?
The three most common reasons for extra mucus or snot are the common cold, sinusitis (infection or inflammation of the sinuses, the air-filled spaces inside the face bones) and hay fever. Each of these conditions cause the lining in the nose to swell up, and to produce extra mucus to flush away infection, irritants or allergens.
Both the swelling and extra mucus lead to nasal congestion. This is when the narrowed passages increase the effort of breathing through the nose. Clearing the mucus by blowing the nose should reduce this congestion somewhat.
At the beginning of colds and for most of the time with hay fever, there’s lots of runny mucus. Blowing the nose regularly prevents mucus building up and running down from the nostrils towards the upper lip, the all-too-familiar runny nose.
Later in colds and with sinusitis, nasal mucus can become thick, sticky and harder to clear.
Further reading: Health Check: what you need to know about mucus and phlegm
Think of “snotty nosed kids”, in particular infants or toddlers who haven’t yet learnt to coordinate the mechanics of blowing their noses. They tend to repeatedly sniff thick mucus back into their nose or allow it to dribble down their upper lip.
Keeping this mucus (rather than blowing it out) is thought to contribute to a cycle of irritation that causes the snotty nose to persist for weeks or longer.
This may be due to the retained mucus acting as a good “home” for bacteria to grow in, as well as fatigue of the “hairs” (cilia) that cleanse the nose by moving along mucus and carrying with it irritants, inhaled debris and bacteria.
Thick retained mucus is also more likely to be transported to the throat rather than gravity working it from the nostrils, leading to throat irritation and possibly a cough. This is the mechanism behind the most common cause of prolonged cough after a viral infection or hay fever, known as the post-nasal drip cough.
So it makes sense to encourage people to blow their nose to remove unwanted mucus.
Although extremely rare, there are a few examples in the medical literature of people blowing so hard they generated pressures high enough to cause serious damage. In most of these cases people had underlying chronic sinusitis or an existing weakness in the structure they damaged after blowing too hard.
These injuries included fractures of the base of the eye socket; air forced into the tissue between the two lobes of the lung; severe headache from air forced inside the skull; and rupture of the oesophagus, the tube that sends food to the stomach.
One study looked at the pressures generated when people with and without a range of nasal complaints blew their noses.
People with chronic sinusitis generated pressures significantly higher than people without a nasal complaint, up to 9,130 Pascals of pressure. They also found blowing by blocking both nostrils generated much higher pressures than blowing with one nostril open.
Another study comparing pressures from nose blowing, sneezing and coughing found pressures generated during blowing were about ten times higher than during the other two activities.
More worrying was their second finding – viscous fluid from the nose had found its way into the sinus cavities after vigorous nose blowing. The researchers said this could be a mechanism for sinus infection complicating some colds, with the introduction of nasal bacteria to the sinuses. But they did not produce evidence for this.
On balance it seems repeated and vigorous blowing of the nose may carry more risk than benefit, even though it seems to be a natural response to nasal congestion.
So looking to remove the need to blow so forcefully is probably a better option.
Decongestants and antihistamines, which you can buy without prescription from pharmacies, reduce both nasal congestion and the volume of mucus.
Decongestants contain ingredients like oxymetazoline and phenylephrine and come in tablets or sprays, and are often included in cold and flu tablets. They work by constricting (narrowing) dilated blood vessels in the inflamed lining of the nose, and decreasing the volume of mucus produced.
While decongestant sprays are effective, they are probably underused due to concerns about nasal congestion when you stop taking them after long-term use (rhinitis medicamentosa). But further studies have questioned this increased risk.
Antihistamines treat nasal congestion associated with hay fever, but may be less effective for treating cold symptoms.
Saline nose sprays have some evidence they work for acute and chronic rhinosinusitis (inflammation of the nasal lining and sinuses), and can reduce the need for medications. They are believed to clear mucus through increasing the effectiveness of the cilia as well as diluting thick and sticky mucus.
A related technique, known as nasal aspiration, is when you squirt liquid saline up the nose with a special medical device to flush out mucus and debris from the nose and sinuses. One study found it lowered the risk of developing acute otitis media (inflammation of the middle ear) and rhinosinusitis.
If you have mucus in the nose, it is probably best to get it out, so blow gently or by clearing one nostril at a time. Use of appropriate treatments can lessen the need to blow, and the force required to clear your nose.
If you are repeatedly blowing your nose you probably have a nasal condition, like hay fever or sinusitis, which should be treated more comprehensively.
And if you see a snotty-nosed kid, please wipe away the mucus discharge for the benefit of all.