Michael R. Eades, M.D.

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August 17, 2005

Vegetarians found lacking

A study appeared in this month’s American Journal of Clinical Nutrition that I’m sure vegetarians of every stripe will hate to see.

Researchers compared the long-chain omega-3 levels (LCPUFA) of 463 vegetarians to that of 196 meat eaters and found that the vegetarians had substantially lower levels of these important fatty acids. The interesting part of this study—to me, at least—is that it didn’t matter how long people had been vegetarians, one year or twenty years, they still had lowered LCPUFA levels. Typically, with long term exposure to either a deficit or an abundance of a particular nutrient, the body adapts over time. Not so with these long chain omega-3 fats, apparently. The researchers report that although the levels of these fats are lower in vegetarians, they are stable.

Vegetarians get a fair amount of alpha linolenic acid, which is the main omega-3 fatty acid in plants. Many people take flax oil, a rich source of alpha linolenic acid, to boost their levels of LCPUFA. MD and I were criticized for writing in Protein Power that flax oil was not an optimum source of LCPUFA, and that people should eat sardines or other fatty fish to get these fats. This study presents data that the conversion of alpha linolenic acid to the longer chained omega-3 fatty acids EPA and DHA is fairly inefficient, at least in vegetarians.

In the introduction to the article, the authors do a good job of succinctly describing these long chain fatty acids and their health benefits:

Apart from being a source of energy, fatty acids have a wide range of physiologic functions. Many fatty acids can be produced endogenously; however, n—3 and n—6 polyunsaturated fatty acids are essential fatty acids that must be provided in the diet. The long-chain metabolites of these essential fatty acids are needed for cellular membrane functions and the production of eicosanoids, which play a role in inflammatory reactions, blood pressure control, and platelet aggregation. These essential fatty acids also influence gene regulation; for example, they act as ligands of peroxisome proliferator-activated receptors that are involved in growth and development. Of particular interest are the long-chain n—3 fatty acids eicosapentaenoic acid (20:5n—3; EPA) and docosahexaenoic acid (22:6n—3; DHA), which are abundant in oily fish and therefore are also referred to as the marine fatty acids. Although their action is not fully understood, these fatty acids probably account for the inverse relation between fish consumption and the risk of developing coronary heart disease and stroke that has been observed in epidemiologic studies (1—4). Apart from its probable cardioprotective effects, DHA is, with arachidonic acid, one of the 2 most prevalent polyunsaturated fatty acids in brain and retinal phospholipids and plays a role in normal neurotransmission and visual function.

Sounds to me like something one would rather have more of than less.

With all the hype about vegetarian diets being more healthful, it should be remembered that along with lowered levels of LCPUFA these diets are deficient in a number of other nutrients as well. For example, vegetarians typically have higher homocysteine levels thanks to their non-existent intake of vitamin B-12 other than in supplement form. Most people, thanks to the anti-meat lobby, think only of folate as being the nutrient necessary to reduce homocysteine. Au contraire, it takes vitamin B-12 as well, which meat eaters have in abundance, keeping their homocysteine levels lower than those of their vegetarian brethren.

Posted by mreades at August 17, 2005 10:42 AM

Comments

Posted by: All your AOE belong to us at September 25, 2006 10:21 AM

Posted by: All your AOE belong to us at September 25, 2006 10:24 AM

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