Here’s what you can eat and avoid to reduce your risk of bowel cancer



It’s not certain why, but fibre has protective effects against bowel cancer.
http://www.shutterstock.com

Suzanne Mahady, Monash University

Australia has one of the highest rates of bowel cancer in the world. In 2017, bowel cancer was the second most common cancer in Australia and rates are increasing in people under 50.

Up to 35% of cancers worldwide might be caused by lifestyle factors such as diet and smoking. So how can we go about reducing our risk of bowel cancer?




Read more:
What’s behind the increase in bowel cancer among younger Australians?


What to eat

Based on current evidence, a high fibre diet is important to reduce bowel cancer risk. Fibre can be divided into 2 types: insoluble fibre, which creates a bulky stool that can be easily passed along the bowel; and soluble fibre, which draws in water to keep the stool soft.

Fibre from cereal and wholegrains is an ideal fibre source. Australian guidelines suggest aiming for 30g of fibre per day for adults, but fewer than 20% of Australian adults meet that target.

Wheat bran is one of the richest sources of fibre, and in an Australian trial in people at high risk of bowel cancer, 25g of wheat bran reduced precancerous growths. Wheat bran can be added to cooking, smoothies and your usual cereal.

It’s not clear how fibre may reduce bowel cancer risk but possible mechanisms include reducing the time it takes food to pass through the gut (and therefore exposure to potential carcinogens), or through a beneficial effect on gut bacteria.

Once bowel cancer is diagnosed, a high fibre diet has also been associated with improved survival.

Dairy is ‘probably’ protective against bowel cancer.
from http://www.shutterstock.com



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Milk and dairy products are also thought to reduce bowel cancer risk. The evidence for milk is graded as “probably protective” in current Australian bowel cancer guidelines, with the benefit increasing with higher amounts.

Oily fish may also have some protective elements. In people with hereditary conditions that make them prone to developing lots of precancerous growths (polyps) in the bowel, a trial where one group received a daily supplement of an omega 3 polyunsaturated fatty acid (found in fish oil) and one group received a placebo, found that this supplement was associated with reduced polyp growth. Whether this is also true for people at average risk of bowel cancer, which is most of the population, is unknown.

And while only an observational study (meaning it only shows a correlation, and not that one caused the other), a study of bowel cancer patients showed improved survival was associated with daily consumption of coffee.

What to avoid

It’s best to avoid large quantities of meat. International cancer authorities affirm there is convincing evidence for a relationship between high meat intake and bowel cancer. This includes red meat, derived from mammalian muscle such as beef, veal, lamb, pork and goat, and processed meat such as ham, bacon and sausages.

Processed meats have undergone a preservation technique such as smoking, salting or the addition of chemical preservatives which are associated with the production of compounds that may be carcinogenic.

Evidence also suggests a “dose-response” relationship, with cancer risk rising with increasing meat intake, particularly processed meats. Current Australian guidelines suggest minimising intake of processed meats as much as possible, and eating only moderate amounts of red meat (up to 100g per day).

What else can I do to reduce the risk of bowel cancer?

The key to reducing cancer risk is leading an overall healthy lifestyle. Adequate physical activity and avoiding excess fat around the tummy area is important. Other unhealthy lifestyle behaviours such as eating lots of processed foods have been associated with increased cancer risk.

And for Australians over 50, participating in the National Bowel Cancer Screening program is one of the most effective, and evidence-based ways, to reduce your risk.




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The Conversation


Suzanne Mahady, Gastroenterologist & Clinical Epidemiologist, Senior Lecturer, Monash University

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

What’s behind the increase in bowel cancer among younger Australians?



File 20181115 194509 4mwn4d.jpg?ixlib=rb 1.1
Bowel cancer was the second most commonly diagnosed cancer in Australia in 2017.
from shutterstock.com

Suzanne Mahady, Monash University; Eleonora Feletto, Cancer Council NSW, and Karen Canfell, UNSW

Bowel cancer mostly affects people over the age of 50, but recent evidence suggests it’s on the rise among younger Australians.

Our study, published recently in Cancer Epidemiology, Biomarkers and Prevention, found the incidence of bowel cancer, which includes colon and rectal cancer, has increased by up to 9% in people under 50 from the 1990s until now.

Our research examined all recorded cases of bowel cancer from the past 40 years in Australians aged 20 and over. Previous studies assessing bowel cancer incidence in young Australians have also documented an increase in the younger age group.




Read more:
Interactive body map: what really gives you cancer?


Bowel cancer includes cancer of the colon and rectum.
Wikimedia Commons

This trend is also being seen internationally. A study from the United States suggests an increase in bowel cancer incidence in people aged 54 and younger. The research shows rectal cancer incidence increased by 3.2% annually from 1974 to 2013 among those aged age 20-29.

Bowel cancers are predicted to be the third most commonly diagnosed cancer in Australia this year. In 2018, Australians have a one in 13 chance of being diagnosed with bowel cancer by their 85th birthday.

Our study also found bowel cancer incidence is falling in older Australians. This is likely, in part, to reflect the efficacy of the National Bowel Cancer Screening Program, targeted at those aged 50-74. Bowel cancer screening acts to reduce cancer incidence, by detecting and removing precancerous lesions, as well as reducing mortality by detecting existing cancers early.

This is important, as bowel cancer has a good cure rate if discovered early. In 2010 to 2014, a person diagnosed with bowel cancer had a nearly 70% chance of surviving the next five years. Survival is more than 90% for people who have bowel cancer detected at an early stage.

That is why screening is so effective – and we have previously predicted that if coverage rates in the National Bowel Screening Program can be increased to 60%, around 84,000 lives could be saved by 2040. This would represent an extraordinary success. In fact, bowel screening has potential to be one of the greatest public health successes ever achieved in Australia.

Why the increase in young people?

Our study wasn’t designed to identify why bowel cancer is increasing among young people. However, there are some factors that could underpin our findings.

The increase in obesity parallels that of bowel cancer, and large population based studies have linked obesity to increased cancer risk.




Read more:
How obesity causes cancer, and may make screening and treatment harder


Unhealthy lifestyle behaviours, such as increased intake of highly processed foods (including meats), have also been associated with increased bowel cancer risk. High quality studies are needed to explore this role further.

Alcohol is also thought to be a contributor to increasing the risk of bowel cancer.

Alcohol is thought to contribute to an increased risk of bowel cancer.
from shutterstock.com

So, should we be lowering the screening age in Australia to people under the age of 50?

Evaluating a cancer screening program for the general population requires a careful analysis of the potential benefits, harms, and costs.

A recent Australian study modelled the trade-offs of lowering the screening age to 45. It showed more cancers would potentially be detected. But there would also be more colonoscopy-related harms such as perforation (tearing) in an extremely small proportion of people who require further evaluation after screening.

A lower screening age would also increase the number of colonoscopies to be performed in the overstretched public health system and therefore could have the unintended consequence of lengthening colonoscopy waiting times for people at high risk.




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How to reduce bowel cancer risk

One of the most common symptoms of bowel cancer is rectal bleeding. So if you notice blood when you go to the toilet, see your doctor to have it checked out.

A healthy lifestyle including adequate exercise, avoiding smoking, limiting alcohol intake and eating well, remains most important to reducing cancer risk.

Aspirin may also lower risk of cancer, but should be discussed with your doctor because of the potential for side effects including major bleeding.

Most importantly, we need to ensure eligible Australians participate in the current evidence-based screening program. Only 41% of the population in the target 50-74 age range completed their poo tests in 2015-2016. The test is free, delivered by post and able to be self-administered.The Conversation

Suzanne Mahady, Gastroenterologist & Clinical Epidemiologist, Senior Lecturer, Monash University; Eleonora Feletto, Research fellow, Cancer Council NSW, and Karen Canfell, Adjunct professor, UNSW

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