Vegetables We’re always being told to tuck into fruit and vegetables to reduce our risk of cancer and other diseases, but few studies have examined the potential benefits of being vegetarian. Until now. A team led by Professor Timothy Key, deputy director of the Cancer Epidemiology Unit, at Oxford University, recently examined the effect of a vegetarian diet on the risk of developing cancer.
The team tracked the number of cancers that developed in more than 61,000 people aged 20 to 89 over a period of 12 years. Just over 32,000 were meat eaters, over 8,000 ate fish but not meat, and almost 21,000 were totally vegetarian. The results, published in the British Journal of Cancer, showed that vegetarians had a 12% lower incidence of any kind of cancer. More specifically they had a 44% lower incidence of stomach cancer, a 53% lower incidence of bladder cancer and a 45% lower incidence of cancers of the blood.
It has to be said that the numbers who developed cancer were relatively small – 3350 altogether, 2204 of which were meat eaters, 317 fish eaters and 829 vegetarians. Just 49 people developed stomach cancer, 85 bladder cancer and 257 cancers of the blood. This makes it difficult to draw definitive conclusions. However, Professor Key observes, "Vegetarians can be reassured that their risk of cancer may be slightly lower than their meat-eating cousins."
Professor Key is himself a vegetarian - although for humane rather than purely health reasons. But the million-dollar question is: does eating more vegetables lower the risk of cancer or is avoiding something in meat and animal products the crucial factor?
Professor Key comments, "The difference in the amount of vegetables consumed between the three different types of diets is fairly negligible although vegetarians do eat slightly more than meat eaters. We know from other studies that meat and processed meat increase the risk of stomach, bowel and bladder cancer. Some studies also suggest that butchers and farmers who work with animals and raw meat have a higher risk of cancers of the blood."
This suggests that it could well be something that vegetarians don’t eat rather than what they do that is the crucial factor. On the other hand a growing body of research is pointing towards a protective role for certain components found in vegetables, although much of this work has been done in the test tube and in animals, while human studies tend to be contradictory.
What does seem clear is that food components work together – for instance compounds found in soya appear to enhance the ability of vitamin D to put the brakes on prostate cancer cells. This could explain how diets as a whole – such as a vegetarian diet - rather than single food components protect against cancer. So what are the best ways to get more veg and less meat into your diet?
Perhaps the best advice is to eat your greens – and yellows, reds and blues. Fruit and vegetables of different hues are rich in what the experts call bioactive compounds, plant chemicals that according to research show promise in cancer prevention.
Here’s a few things you can do
- Aim for two vegetarian days a week. It’s better for the environment too.
- Cut consumption of red and processed meats such as bacon, salami and sausages. The World Cancer Research Fund/American Institute of Cancer research recommend consuming less than 500 grams a week – that's around 18 oz.
- Make sure at least 50% of your plate contains vegetables and aim for eight to 12 portions a day rather than five, which is the minimum recommended to help prevent disease.
- Brassica or cruciferous vegetables, such as broccoli, cabbage and Brussels sprouts are rich in compounds called glucosinolates that, when broken down, may interrupt cancer 'pathways'.
- Even more potent are three-day broccoli sprouts – buy seeds from health food shops and garden stores and sprout them yourself or you can buy them ready sprouted.
- Onions and garlic are rich in sulphur compounds generated by chopping or chewing. In studies these have shown promise in helping to bowel, oesophageal and prostate cancer.
- Compounds called polyphenols in berries plus other nutrients may help prevent cancer development. Sprinkle them on cereals, or whiz into smoothies.
- Lignans are plant chemicals found in cashew nuts, cranberries, linseed, peanuts, raisins and rye. Studies suggest they may help reduce risk of hormone-dependent cancers, such as breast and prostate.
- Selenium found in brazil nuts and fish looks promising against a number of different cancers including prostate.
- Diets high in soya beans and their products such as tofu and miso are linked to lower incidence of cancer. A compound called genistein found in soya inhibits breast, prostate and bladder cancer in animals and in the test tube causes the death of lung, prostate, bladder and breast cancer cells.
- Vitamin D deficiency is linked to a higher risk of a number of cancers including colon, prostate and breast cancer. The best source is sunlight but you can also get it from fish, eggs and sun-dried shitake mushrooms.
- Tomatoes, especially when cooked, are a rich source of plant chemicals called lycopene that may help protect especially against prostate cancer.
- Cut saturated fat. Saturated animal fats are linked to a higher incidence of cancer, especially of the colon, breast and prostate.
First published February 15, 2010