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The morality of eating animals is beyond the scope of this article, but there is a great deal of evidence about the pros and cons of the vegan nutritional style as they relate to health

Vegan nutritional style- no animal products at all

The vegan nutritional style requires eating absolutely no animal products—no meat, no fish, no dairy, no eggs, and no honey. People become vegans from profound convictions concerning the morality of killing animals to be eaten, or from profound belief that a vegan nutritional style could be the best path to healthy living. The morality of eating animals is beyond the scope of this article, but there is a great deal of evidence about the pros and cons of the vegan nutritional style as they relate to health.

The vegans best known to medical science are members of a Christian religious group known as the Seventh Day Adventists. Largely through the efforts of scientists at a Seventh Day Adventist educational institution, Loma Linda University, generations of Adventists have been studied in decades of clinical trials.

Not every vegan is a Seventh Day Adventist, of course, and not every Seventh Day Adventist is a vegan. Since veganism is the primary difference in lifestyle among Seventh Day Adventists, however, scientists can easily identify pros and cons of vegan lifestyle.

Studies of Seventh Day Adventists and the vegan nutritional style began in 1960. Just two institutions, Loma Linda University and Harvard Medical School, have complied over 300 studies of this well-known religious group. One of the most interesting findings of the research on Adventists concerns vegan diet and risk of cancer.

Vegan Nutritional Style and Cancer Risk

Some kinds of cancers are very rare among Seventh Day Adventists. Since very few Adventists smoke, lung cancer is almost unheard of in this group. Possibly because of the fiber in the diet, colon cancer rates are about half those of the general population of the United States.

Scientists have been surprised to learn, however, that Seventh Day Adventists develop breast and prostate cancer at about the same rates as other groups in the United States. Many Adventists substitute soy for meat at one or more meals every day. Since breast and prostate cancer rates are lower in Asian countries where soy is a dietary staple, scientists wondered why Adventists did not enjoy similar protection from these two common, often deadly, diseases.

The answer seems to be that a little soy is protective while a lot of soy is harmful. The amount of soy eaten per day in a typical Chinese, Japanese, Korean, or Vietnamese diet is only about half an ounce (15 g) a day. That amount of soy provides all the phytoestrogens the human body can absorb.

Larger amounts of soy, such as the 4 to 8 oz (approximately 100 to 200 g) of soy protein a day eaten as soy burgers and vegan "cutlets" provides no additional phytoestrogens that the body can use. The process of creating texturized soy protein, however, may introduce artificial chemicals into the body that are themselves carcinogenic. The first lesson of the pros and cons of vegan lifestyle taught us by the Seventh Day Adventists is that eating plant foods as a substitute for meat is not healthy. The best vegan diet eats plant foods for their own value.

Pros and Cons of Dairy Consumption

Scientists have also studied Seventh Day Adventists' consumption of dairy products. Some Adventists, as strict vegans, consume no dairy products. Other Adventists consume no meat but drink milk and eat dairy products as an important source of protein. Many Adventists eat no meat but drink 3 or more glasses of milk a day. Studies of Adventists reveal a striking relationship between the consumption of dairy products prostate cancer in men.

The relationship between drinking milk and prostate cancer is not what might be expected. Low-fat milk, rather than high-fat milk, has greater effect on the risk of cancer of the prostate. Adventist men who drink no milk at all, however, were 20 to 80 per cent less likely to develop prostate cancer than men who drink at least 1 glass a day. The more milk consumed, especially the more low-fat milk consumed, the greater the risk of prostate cancer.

Based on studies in Scandinavia, scientists expected to find that Adventist women who did not drink milk had lower rates of ovarian cancer than Adventist women who did. The research studies, however, did not reach this conclusion.

Vegan Lifestyle and Heart Disease

Another clear finding of the studies of Seventh Day Adventists is that vegans have lower rates of heart disease. This also surprises scientists. Although vegan Seventh Day Adventists consume much less saturated fat than Adventists who eat meat, they also get much lower amounts of omega-3 fatty acids, such as those in fish—or at least so the scientists thought at first.

Studies of Seventh Day Adventists since about 1980 have shown that the omega-3 fatty acids in nuts are as protective as those in fish. Adventists who regularly eat raw nuts and seeds have all the advantages of people who take fish oil, without having to take fish oil supplements or eat fish.

Longer Life with a Vegan Lifestyle?

Fifty years of scientific research has shown that Seventh Day Adventists indeed live longer than non-Adventists. The average woman who is an Adventist lives 4 years longer than the average woman who is not an Adventist. The average man who is an Adventist lives 7 years longer than the average man who is not an Adventist. Vegan lifestyle, however, is just one factor in the longevity of Seventh Day Adventists.

Scientists have identified a cluster of health factors tied to longevity:

  • Avoidance of overweight
  • Avoidance of smoking
  • Regular physical activity
  • Consumption of nuts (a source of omega-3 fatty acids)
  • Vegan diet

Of all these factors, vegan diet makes the smallest contribution to longevity. Never smoking, avoiding weight gain, exercising regularly, and even eating nuts were all more important to living a long life than keeping a strictly vegan diet.

The fact that a vegan diet does not guarantee you will live longer, of course, does not mean you should not follow a vegan diet. If your personal principles exclude the eating of meat, by all means, you should eat a vegan diet. To live a long and healthy life, however, it is also important not to smoke, not to get overweight, to eat nuts and seeds, and to exercise regularly.

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  • Phillips RL, Garfinkel L, Kuzma JW, Beeson WL, Lotz T, Brin B. Mortality among California Seventh-day Adventists for selected cancer sites. J Natl Cancer Inst 1980.65:1097–107.
  • Photo courtesy of Michael Coghlan by Flickr :