Vegetarian diets

In 2003 the American dietetic Association and the Dietitians of Canada issued a position statement based on 256 references to research studies. They conclude that vegetarian diets must be carefully planned to avoid deficiencies of calcium, zinc, iodine, vitamin B12, vitamin D and omega 3 fatty acids. Otherwise, if nutritionally adrequate, they provide health benefits in prevention and treatment of certain diseases.

Compared with most non-vegetarian diets, vegetarian diets tend to be associated with an improved coronary heart disease risk profile, including lower low density lipoprotein ( LDL) cholesterol levels (Burr AJCN 1988; 48: 826-29), lower incidence of diabetes (Snowden Am J Pub Hlth 1985; 75: 507-12), reduced clotting factors (Haines Throm Rs 1980; 19: 139-48) and lower systolic and diastolic blood pressure (Sanders, Hum Nutr: Appl Nutr 1987; 41: 101-8). Many vegetarians also abstain from smoking and this further contributes to a lower coronary heart disease (CHD) risk.

Vegetarians and vegans have higher plasma levels of antioxidants such as tocopherol and carotenoids and these may protect against oxidative modification of LDL. Lower levels of clotting factors (II, V, VII, X), and higher levels of antithrombin III and fibrinolytic activity have also been reported. The effect on blood pressure cannot be explained solely in terms of the absence of meat or meat protein - it remains to be determined.

An increasing phenomenon in the Western world is restraint, rather than total exclusion of meat eating. Such restraint is often limited to red meat, with fish and poultry being included more regularly.

The benefits of a vegetarian diet are not unique. An omnivorous diet that is low in total and saturated fat and contains plenty of fruits, vegetables and wholegrain cereals and small amounts of lean red meat (as in the Mediterranean diet) may be just as effective as a vegetarian diet in terms of reducing coronary heart disease (CHD) risk. (National Heart Foundation Policy Statement, 1997).

The absence of meat is not a major factor for the beneficial effects of a vegetarian diet. Professor Jim Mann from Otago University recently completed a meta-analysis of all cohort studies on the health advantages of vegetarian eating; he found that while they had a lower risk of CHD, the facts regarding cancer were not so clear cut. He also highlighted that vegetarians are generally healthy not because their diet is meat-free, but because their diet was richer in nuts, wholegrain cereals, fruit and vegetables.

Inclusion of some low-fat meat and fish does not seem to be harmful and it may be beneficial in lowering the risk of nutrient deficiencies (Walter Nut Rev 1997; 55 (1): S 61-68).

A study conducted on 36 overweight women at the Baker Institute by Professor Nestel showed that eating a low fat diet (20g fat/day) and 150g lean red meat 5 times a week resulted in 9% weight loss, 12% reduction in cholesterol, 7% reduction in blood pressure, 17% reduction in triglycerides and 28% improvement in artery elasticity. The women on the soybean diet (130g soy beans 5 times a week) had similar results to the meat diet – in other words, the soy bean diet did not outperform the meat diet. Another interesting finding from this study was that modest weight loss i.e. 5-10kg, was enough to reverse the adverse effects of being overweight, such as high blood pressure, high cholesterol and glucose intolerance; it was the first demonstration that artery elasticity was reversible with weight loss. Inelasticity can worsen blood pressure and increase the risks of cardiovascular events. Similar results have been obtained with men (Kestin et al. AJCN 1989; 50: 280-7). However, eating 150g red meat 5 times a week is still not recommended because it may increase the risk of colon cancer, and is environmentally unsustainable. The diet needs to be more varied to ensure adequate intake of other nutrients and phytochemicals e.g. fish, legume dishes, chicken meals need to be incorporated into the weekly menu.

Further evidence supporting the notion that healthy omnivorous diets can be just as good or even better than vegetarian diets comes from a recent study by Prof Neil Mann (1999). This study found plasma homocystine concentrations (an independent risk factor for vascular disease) were lower in omnivores compared to vegans. In another study by Thomas et al (Lipids 1996; 31 (2): 145-51) the saturated fat content of fat cells using magnetic resonance spectrometry in lacto-ovo vegetarians was equal to that of omnivores. However, vegans had 30-40% less saturated fat in their cells. Lacto-ovo vegetarian diets can be high in fat and saturated fat due to intakes of milk, cheese, fats/oils and foods containing these e.g. cakes etc.

Britains National Health & Lifestyle Survey has been monitoring the health of a random, nationwide sample of 9000 adults drawn from all ages and social and economic backgrounds. The two major findings were:
1. People who ate raw/salad vegetables 3-4 times a week suffered up to 50% less heart disease and cancer than non-salad eaters and it made no difference how much meat they ate.
2. Vegetarians in Britain have been found to have exactly the same risk of colon cancer as meat eaters. Nutrition experts agree that there is little convincing evidence that meat itself is ‘bad’, it only matters if you eat so much that you have not got room for anything else and it simply distorts the diet.

The “Food, Nutrition and the Prevention of Cancer: a Global Perspective” 1997 by the World Cancer Research Fund & American Research Institute for Cancer Research, Washington DC reviewed all the evidence and concluded:

“If eating meat, use as a condiment. If eaten at all, red meat should be limited to less than 80g per day. It is preferable to choose fish, poultry or meat from non-domesticated animals in place of red meat. Diets high in red meat (beef, pork, lamb) may increase the risk of bowel cancer and possibly breast, pancreas, prostate and kidney. While the fat, protein and iron content of meat – as well as the method used to cook it – have all been considered for possible explanations, it is not exactly known why a high meat diet is linked with an increased risk of cancer. It may be that meat does not cause cancer per se, but that meat rich diets simply don’t provide as much protective plant foods. As there is only so much room on your plate, be sure you maximise your protection from cancer by filling it first with a variety of plant foods, and if desired, using a small amount of meat for flavouring.”

In Britain, red meat intakes have been dropping while colon cancer rates have been going up. Mediterranean people today have high meat intakes, but have less colon cancer than Brits - presumably because they eat more and a greater variety of protective plant foods.

Australians consume on average about 100g –200g of meat per day and the recommended intake is less than 80g per day. 40% of today’s world grain production is used for meat-producing livestock. This conversion of cereal grains and other foods to animal products involves significant losses of energy. One kilogram of beef requires 5kg of grain. If meat consumption were lowered, then more cereal grains and other food components might be used to improve the world’s nutrition.

These studies/observations suggest that eating a wide variety of foods may be superior to food habits that exclude certain food groups.

Last Updated: March 28, 2001