There are over 200 different types of cancer, which reflects the different types of cells we have in our bodies. Cancer is rapidly becoming a disease that many of us will experience within our lifetimes, and this is mainly because we are living longer. By far the most diagnoses of cancers affect us in our elderly years (over 60% of all cancer diagnoses), possibly due to a number of factors including the body’s declining ability to naturally halt the development of tumours, longer exposure to carcinogens over a lifetime, and the fact that our body’s cells become less and less able to repair themselves properly.
However, our lifestyle can have a profound effect on whether we can swerve the cancer bullet. The science behind the link between cancer and lifetstyle is growing year on year and it is now widely recognised that lifestyle can account for around 40% of all cancers, and diet in particular accounts for around 10%.
If you’re looking for just one diet that may reduce your odds of developing cancer, then there is none better than the Mediterranean diet. This diet focusses largely on fresh fruit and vegetables that are seasonally and locally grown, fish, olive oil, nuts and seeds and much lower levels of red meat than in northern European diets. Although statistics are changing with each passing decade, traditionally people of the Mediterranean countries have lower levels of obesity, heart disease and cancer, and people specifically on the fruit, vegetable and fish rich diet of Sardinia were living much longer lives.
Meat vs. vegetarian diet
The World Health Organization (WHO) recently advised that eating a lot of processed meats such as sausages, bacon, ham and pâtés is strongly linked to the causation of bowel cancer. Processed meats are those that have gone through preservation processing such as smoking, curing, adding preservative chemicals or using salting to give the meat its distinctive flavouring and texture. There are two things that are considered to be carcinogenic (cancer forming) with processed meat: the first is the addition of nitrites to kill bacteria in the meat, and the second is the formation of compounds called PAHs during the smoking process. This is also true when we cook meat at home by barbequing meat over smoking charcoal. However, this doesn’t mean that you need to exclude these types of foods from your diet completely, there are recommended health limits set, which currently stands at 70g of any processed meat per day.
Vegetarian and vegan diets have often been linked to lower risks of bowel cancer for two main reasons: firstly, vegetarian diets are higher in dietary fibre and therefore speed up the transit of food through the gut which reduces the time that foods have contact with the gut lining. Secondly, vegetarians tend to eat more plant foods which are higher in a range of compounds that are believed to have a strong antioxidant effect in the body, which may provide greater protection against cancer. More and more studies are now linking “phytochemicals” such as flavonoids and polyphenols with reduced cancer risk, and these can only be found in plant-based foods.
A recent survey by Cancer Research UK suggested that three quarters of Brits did not know that there was a direct link between obesity and cancer. Many people know that being overweight may cause heart disease and diabetes, but the link to cancer appears to have become lost in communication. Fat cells are like hormone factories and produce female hormones like oestrogen that can be linked to cancers such as breast and ovarian cancer in women and prostate cancer in men. Too much body fat, particularly the type that accumulates around the waist, can also switch off the body cells’ ability to react to insulin, which is one of the causal factors in type 2 diabetes. One of the consequences of this is a blood rise in growth factors which is a green light for any cancer cells to divide and replicate and therefore there is a link between high blood glucose and cancer
There are two main groups of fat that we’re interested in from the point of view of protection against cancer: saturated and unsaturated fat. Saturated fat are those that exist as a solid at room temperature and include coconut oil, palm oil, butter, lard and shortening. Saturated fat is often linked to heart disease because it is implicated in the increased blood levels of “bad cholesterol”, but saturated fat could also be linked to a higher risk of cancer too. However, it has to be noted that the scientific evidence for this is currently inconclusive, simply because there are not enough large long term studies to back up this claim. The difficulty with these studies is separating people who eat a lot of saturated fat from those who eat high calorie diets and maintain a sedentary lifestyle. We do know that there is a strong link between lack of exercise, obesity and cancer. That said, switching to unsaturated fats for cooking is considered more healthy because there is enough evidence to suggest that consuming more virgin, cold-pressed plant oils higher in mono and polyunsaturated could be beneficial rather than detrimental to our health. Similarly, choosing fish over red meat (which is high in saturated fat) once or twice a week is a great way to introduce some healthier habits into our lifestyle, because fish is naturally higher in polyunsaturated fats, some of which have an anti-inflammatory effect in the body.
The health-conscious among you might already know that high salt intake can contribute to raised blood pressure, a major risk factor for strokes in the UK. But did you know that high salt may also be a causal factor behind stomach cancer too? The World Cancer Research Fund International published a report this year showing a link between salt-preserved fruit, vegetable and fish and stomach cancer – this link was established in Asian cultures where consumption of salt-preserved foods is very high, and countries that consume a lot of salt in processed food. Salt may damage the lining of the stomach creating an environment for the cancer-causing bacteria in the stomach known as H.Pylori.
High alcohol consumption is directly linked to the increased risk of many cancers, but one of the most prevalent cancers that could possibly be avoided by moderating alcohol intake is breast and ovarian cancer. The exact cause is unknown, but one of the problems with alcohol is that when it is metabolised, it is broken down into a substance called acetaldehyde, which is not only responsible for your hangover but also can cause genetic mutations.
In women, alcohol may also increase the level of circulating oestrogen, which is not great news for oestrogen-sensitive tumours like breast and ovarian cancer. Alcohol may also be responsible for about 11% of bowel cancer cases according to Cancer Research UK, and could increase your risk of getting the disease by 23% according to the 2007 European Prospective Investigation into Cancer and Nutrition (EPIC) study.
Being physically active is linked to lower risks of breast, womb and bowel cancer. The largest studies conducted have shown that being physically active can reduce the risk of colon (but not rectal) cancer by up to 25%, which is a pretty impressive. Exactly why exercise keeps down cancer risks isn’t entirely known. Exercise does keep our body fat levels down, which could be one link, but it also releases a number of hormones (and neurotransmitters) and stabilises others (such as insulin, the hormone responsible for taking sugar out of our blood and into cells – but it also tells some cells to replicate, that would also include cancer cells!). One infamous neurotransmitter that physical activity releases is endorphins, and these can help keep stress at bay. Stress can interfere with our immune system and therefore our ability to keep our cells healthy.
Exercise also helps keep bowels healthy by ensuring that food passes through at a proper rate, and this reduces the time that certain types of food like meat has contact with the bowel wall. It is this contact that predisposes us to cancer risk, because it damages the sensitive lining.
We’re a nation of sun-worshippers and when the sun isn’t out, some of us head to tanning salons. According to the Daily Mail in June last year, there has been an 80% increase in the demand for tanning salons from both genders as we strive to emulate the skin tones of our favourite celebrities. Both tanning salons and sunrays darken our skin by exposing it to ultraviolet radiation, but this is also reflecting in an increase in a serious type of skin cancer called melanoma. We need the sun, as it’s our principal source of vitamin D during the summer months, but we only require around 10-20 minutes of it – just enough time to avoid being burned. Being out in the sun is a great way to boost mood and wellbeing and vitamin D may also be cancer-protective, but being directly in the sun for extended periods, enough that burns our skin, is a health risk.
It is well-known that smoking tobacco significantly increases our risk of lung cancer and not smoking tobacco reduces it. However, if you do smoke, some doctors suggest that you increase your vitamin C for two main reasons: firstly, smoking has been linked with vitamin C depletion. Vitamin C is a water soluble vitamin and therefore it doesn’t hang around in our body for very long before it is excreted in the urine. Some research has shown that vitamin C levels in smokers is even lower, possibly because the body is using up vitamin C at a higher rate than non-smokers. Taking vitamin C supplements could be one way to temporarily combat this, but the only long term solution is to quit smoking and then consider a diet that is rich in antioxidant foods such as the Mediterranean diet.
BBC Health News
Cancer Research UK (2016) www.cancerresearchuk.org
Drink Aware: alcohol and cancer
Katragadda et al (2009) Emissions of volatile aldehydes from heated cooking oils. Food Chemistry 120; 59-65
World Cancer Research Fund International (2016) Diet, Nutrition, physical activity and stomach cancer
World Health Organization guidance on meat
Seb is a writer and blogger of food and nutrition. He holds a bachelors and a masters degree in nutrition science, and has studied sports and exercise nutrition at postgraduate level. He specialises in plant-based nutrition and believes passionately that we can all live with a little less meat.