[Nutrition and health--potential health benefits and risks of vegetarianism and limited consumption of meat in the Netherlands].Ned Tijdschr Geneeskd 2003; 147(27):1308-13NT
In the latest Dutch national food consumption survey (1998) just over 1% of subjects (about 150,000 persons) claimed to be vegetarians; however, a much larger group (6% or approximately 1 million persons) ate meat < or = once a week. Vegetarianism can be subdivided into lacto-vegetarianism (a diet without meat and fish) and veganism (a diet without any animal foods whatsoever, including dairy products and eggs). A recent meta-analysis showed that vegetarians had a lower mortality from ischaemic heart disease than omniovorous subjects; however, cancer mortality and total mortality did not differ. Although a high consumption of red meat, which is rich in haeme iron and saturated fat, may increase the risk of cardiovascular disease and some types of cancer, this does not apply to white meat and fish. In fact, the most important protective effect would seem to be derived from the consumption of unrefined vegetable products (whole-grain cereals, vegetables, fruits, nuts and legumes) and fish. In other words, a prudent, omnivorous diet with moderate amounts of animal products, in which red meat is partly replaced by white meat and fish (especially fatty fish), together with the consumption of ample amounts of unrefined vegetable products, is thought to be just as protective as a vegetarian diet. On the other hand, the omission of meat and fish from the diet increases the risk of nutritional deficiencies. A vegan diet, in particular, leads to a strongly increased risk of deficiencies of vitamin B12, vitamin B2 and several minerals, such as calcium, iron and zinc. However, even a lacto-vegetarian diet produces an increased risk of deficiencies of vitamin B12 and possibly certain minerals, such as iron. Data from the latest Dutch food consumption survey suggest that 5-10% of all inhabitants of the Netherlands (up to 1 million persons) actually have a vitamin B12 intake below recommended daily levels. In medical practice, the possibility of vitamin B12 deficiency in subjects consuming meat or fish < or = once a week deserves serious consideration. In case of doubt, evaluation is indicated using sensitive and specific deficiency markers such as the levels of methylmalonic acid in plasma or urine. Alternative dietary sources of vitamin B12 instead of meat are fish (especially fatty fish is a good source of vitamin B12), or a vitamin-B12-supplement.