epidemiologista

Trying to make sense of nonsense

Long live the vegetarian?

You might have already noticed, but this week is the National Vegetarian Week, an annual event coordinated by the Vegetarian society highlighting the benefits of vegetarianism. Events promoting a meat-free lifestyle are happening throughout the country in an attempt to get more people to go veggie. While there are a multitude of reasons why you might decide to lay off the flesh, the Vegetarian Society boil it all down to three reasons on their website: the animals, the environment and health & wellbeing. As personal opinions on the first two of those seem to be made up in most of us, the latter is receiving most attention this week.

Call it a lucky coincidence, but at the start of National Vegetarian Week The World Cancer Research Fund (WCRF) has released a report, which, among a lot of other things, advises to limit the intake of red meats and processed meats. Stories of correlations between different kinds of meat and bowel cancer are nothing new; they’ve reached the newspapers time and time again. What’s different this time, is that the WCRF has labeled the evidence linking the two together as ‘convincing’ for the first time. Moreover, the WCRF review also raised the evidence for foods high in fibre, pulses, fruit and vegetables preventing bowel cancer from ‘probable’ to ‘convincing’.

While all that sounds very enticing, it doesn’t directly support the case for vegetarianism. Meat-eaters can choose their meats wisely and as long as they don’t support a solely carnivore lifestyle they could rival any vegetarian in fruit and veg intake. However, there are also some studies comparing the rates of cancer between vegetarians and omnivores. One of these studies is the European Prospective Investigation into Cancer and Nutrition, better now as EPIC. The Oxford arm of this European wide investigation has specifically looked at vegetarians, vegetarians who eat fish (fish-eaters for short) and meat eaters. They followed over 33,000 meat-eaters, 21,000 vegetarians and almost 9,000 fish-eaters over 10 years and assessed the cancers they developed over this period.

Overall, they found that both vegetarians and fish-eaters had a lower risk of being diagnosed with cancer compared with meat-eaters. The risk was particularly lower for both groups of vegetarians in stomach cancer, ovarian cancer, bladder cancer and cancers of the lymphatic and haematopoietic tissues (i.e. leukemia and other cancers of the blood). The effects ranged from a 15% to 71% decrease, which is a truly amazing find. Diet appears to one of the key players in cancer development, but it has appeared rather difficult to put a finger on what elements of diet play a role in the prevention or causation of cancer. A study that finds an effect of this magnitude is thus a real treasure.

However, vegetarians are a weird bunch of people: compared to the general population, they have lower BMIs, are more physically active and gain less weight over time.  Or in other words: they tend to be more health conscious. Where meat-eaters are a greatly diverse lot, with some that will be regulars at fast food chains while others enjoy a healthy diet, vegetarians tend to lean more towards the latter. This makes it harder for researchers to weed out why exactly vegetarians are healthier: is it their lack of meat, their active lifestyles, or another aspect of their lifestyles that is causing their lower cancer rates?

The EPIC study took some of these lifestyle factors into account, be it in a crude way, and still found some beneficial effects of a vegetarian diet. However, that is not to say that meat-eaters, with a balanced diet, would necessarily be at a higher risk of cancer. New research could compare health-conscious meat-eaters with vegetarians to see whether the beneficial effects in vegetarians are due to their lack of meat or their general healthy lifestyle. A healthy lifestyle may thus not be the most convincing reason to go veggie. But as one of those pesky leaf-eating vegans myself, I have to say that the other reasons are very compelling indeed.

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