Vegans, vegetarians, diets and health-part 2

I’m devoting this weeks’ post to the current knowledge of the health effects of a vegetarian diet after discussing the vegan diet’s health effects in a post a fortnight ago.

The term vegetarian is quite broad, but for simplicity’s sake we’ll define vegetarians as those who avoid meat, fish/seafood and poultry, and do eat milk and eggs. It’s estimated (by a Harris Interactive poll) that 2.8 percent of the American population is vegetarian.

Much has changed in attitudes towards vegetarian lifestyles in the past decades. As a lifelong vegetarian, the first question I used to get was “Where do you get your protein?” The answer to this question is simple: Contrary to popular myth, plants--especially pulses (peas, beans and lentils), nuts, seeds and grains--have plenty of protein. Animal protein is considered a complete protein, meaning it has all essential amino acids in every bite. We now know that incomplete proteins can be stored in the body for many days to be combined with other incomplete proteins. Since different plant foods together contain all essential amino acids, it doesn’t matter if the proteins are complete or incomplete, and it’s also no longer recommended to bother with combining those different proteins in the same meal. Protein isn’t a problem.

The second question was usually “So what do you eat?” That led to an invitation to join us for a home-cooked meal that I’d prepare, or to a recommendation to try one of the many excellent vegetarian restaurants that prove the case that vegetarian food can be varied, extensive, deeply satisfying and extremely pleasurable.

A vegetarian diet is now much more accepted, vegetarian options have become much more popular, and vegetarian menus are less of a mystery. Many non-vegetarians are looking to eat more vegetarian foods, and it’s now proven that a healthy vegetarian diet is nutritionally adequate, doesn’t lead to any deficiencies of macro or micro nutrients and needs no supplementation. What’s also becoming quite clear is that vegetarian diets even confer some health protection.

As promised, I’m going back to The American Journal of Clinical Nutrition upcoming supplement on vegetarian, vegan and plant-based diets and their effects on health. A paper by Gary E. Fraser provides a balanced summery of the current science.

As you can imagine, studying large vegetarian cohorts is no easy task. There are a few such large cohorts. The California Adventists have been studied since 1958 and the study’s ongoing. The Seventh-day Adventist church is a Christian denomination that observes Saturday as the day of worship, but it’s also known for promoting a “healthy message,” including a vegetarian diet and avoidance of alcohol, caffeinated drinks, tobacco (they’ve been denouncing smoking for 150 years, well ahead of the medical community) and illegal drugs. Not all Adventists are vegetarian, so the effect of vegetarianism can be isolated within the Adventists. Other large study cohorts include the Health Food Shoppers’ Study and the Oxford Vegetarian Study both from the UK, and the German Heidelberg Vegetarian Study.

Fraser finds consistency in outcomes of vegetarian lifestyles across studies for the following considerations:

• Coronary heart disease is clearly lower for vegetarians. A combined analysis of these cohorts shows that non-vegetarians have 32% higher heart disease mortality than do vegetarians.

• Total LDL cholesterol is lower in vegetarians.

• Vegetarians are thinner than non-vegetarians.

• The risk of diabetes and hypertension is probably lower for vegetarians across studies.

Where Fraser finds inconsistent results is in the incidence of colon cancer. There’s general agreement from studies of non-vegetarians that red meat consumption increases the risk of colon cancer. The Adventists studies show that vegetarian Adventists indeed have a lower incidence of colon cancer, but the EPIC-Oxford study doesn’t show that vegetarians fare any better than the general British population. This of course demands explanation and further study.

Fraser concludes:

“Much remains to be understood. However, it seems clear that vegetarians experience less CHD (coronary artery disease) than do others. Their risk factor status would lead us to expect this result. The evidence that risk of diabetes is less in vegetarians is highly suggestive, although as yet it comes from cross-sectional work and mainly from California vegetarians. Again, what is known of causal factors in diabetes would lead us to expect this result. Body weight is lower in vegetarians and much lower in California Adventists. LDL cholesterol is lower in vegetarians, and this is probably true for blood pressure and risk of treated hypertension. The reasons for the blood pressure association are not well understood, and more research may refine our understanding of this.

Studies in both California and the United Kingdom are fairly consistent in finding at least moderate reductions in all-cause mortality in vegetarians, in comparison to other subjects living in the same communities. This would be expected on the basis of reduced cardiovascular mortality, unless some other presently unrecognized cause of death is increased in vegetarians. As suggested by the British work, it is also likely that there are other ways to similarly decrease mortality (the health-conscious nonvegetarians) aside from a dietary habit that is fully vegetarian.”

Vegans and vegetarians choose this lifestyle for many reasons, and the personal health advantage isn’t necessarily the main incentive to abstain from animal products. In fact, I don’t know if the health effects of these diets are a good enough reason for those who enjoy the taste of meat to give it up altogether, and I don’t think that there’s good evidence to suggest that eating quality meat in moderation is all that harmful.

On the other hand, there’s plenty of support for the recommendation to lower the (very high) consumption of red and processed meat in the average American diet.

A very recent study in the Archives of Internal Medicine followed half a million participants and found that red- and processed-meat intakes were associated with modest increases in total mortality, cancer mortality and cardiovascular disease mortality, and that the higher the red- and processed-meat intake, the higher the risk. The study of course cannot tell if it’s the meat that’s causing harm, or if those who eat lots of meat substitute it for beneficial foods, such as whole grains, fruits and vegetables.

There also is ample support for the advice to consume more fruits, veggies and whole grains. I’ve devoted several posts to that, and the evidence continues to accumulate: Just a few days ago, a very large prospective study, which followed more than 450,000 Europeans from ten countries for an average of almost nine years, showed that high consumption of fruit and vegetables is associated with a reduced risk of colon cancer.

My conclusion is that, from the health point of view, there’s plenty of evidence to suggest we should lower our consumption of animal products (especially red and processed meat) and increase our intake of plant-based foods, especially fruits and veggies.

No discussion of plant-based diets (as opposed to animal-based diets) is complete without getting into the impact our eating habits have on the environment, but that’s for another post.

Dr. Ayala