About one-third of cancers are estimated to be caused by diet, body weight and physical inactivity – all modifiable lifestyle choices. Keeping a healthy body weight and exercising for 30 minutes a day are pretty straightforward ways to offset cancer, but it can be hard to keep track of the latest advice regarding food, especially when apparently contradictory information floods the media from one week to the next.
In this article we take you through what’s known to increase the risk of cancer, what’s known to reduce the risk and those tricky ones in between – sometimes cause and sometimes prevent cancer.
For more information on General health, see Food and health.
What increases your risk of cancer?
Frying, toasting and baking some starchy foods to the point where they go dark brown can cause the formation of acrylamides, which have been found to cause cancer in animals – though not humans as yet. The International Agency for Research on Cancer (IARC), an international agency that’s part of the World Health Organization, lists acrylamide as a class 2A carcinogen – that is, it’s probably carcinogenic to humans. The main culprits are potato chips and other fried and baked forms of potatoes, as well as toast and biscuits. When you cook these foods, keeping them light brown rather than dark or burnt can reduce acrylamide formation. It’s also found in coffee.
It’s popularly believed that sugar feeds cancer. Therefore, proponents argue, eliminating all refined sugars and other sources of sugar and carbohydrates such as bread, pasta, fruit and sweet foods and drinks can prevent or halt the progression of cancer. All cells, including cancer cells, use sugar for energy. But if they don’t get it from food, they get it from breaking down protein and fat, so starving yourself of sugar won’t help stop cancer. Furthermore, cancer sufferers need excellent nutrition to counteract the effects of treatment, and depriving yourself of entire food groups such as carbohydrates is counterproductive.
Nonetheless, that doesn’t mean a lot of sugar is okay. Emerging research suggests that excess insulin – which occurs with fast, high peaks of glucose in the bloodstream – can drive the growth of cancer cells. Also, excess sugar can lead to weight gain, and obesity is a risk factor for cancer. So it makes sense to eat a low glycaemic diet and to avoid the sugar peaks associated with excess insulin.
Artificial sweeteners, which had been shown to cause cancer in animals at extremely high doses, are considered safe for humans.
Red and processed meats
There’s convincing evidence that red meat (beef, pork, lamb and goat) and processed meat (meats preserved by smoking, curing, salting or chemical preservatives, such as hot dogs, ham, bacon and salami) increase the risk of colorectal cancer. Experts from the World Cancer Research Fund recommend limiting red meat to less than 500 grams per week, and avoiding processed meats. They also recommend that children should not be given processed meats at all.
Salt and salted foods damage the lining of the stomach, and high-salt diets are linked with stomach cancer.
There is convincing evidence that alcohol, even in small amounts, increases the risk of cancer of the mouth, pharynx, larynx, oesophagus and breast, as well as colorectal cancer in men. It may also increase the risk of colorectal cancer and liver cancer in women. Alcohol in mouthwash is also linked with oral cancer. In recognising the potential cardiovascular benefits of small amounts, authorities recommend limiting alcohol to less than one drink per day for women and two for men.
But it seems not all alcohol is created equal – see The Red Wine Paradox for more.
Myth busting: acidic foods and cancer
Some people maintain that eating acidic foods or foods that otherwise make the body more acidic enhance cancer cell growth and should thus be avoided in favour of ‘alkalinising’ foods.
Fact: The body’s acid-base balance is tightly regulated by the respiratory system and kidneys, and is virtually impossible to change – even a slight change in pH can be life-threatening .