Advantages and Disadvantages of a Vegetarian Diet - Part 1

The potential advantages or disadvantages of either a vegetarian or omnivorous diet will vary to a great degree depending on the selection of specific food items that comprise the diet of the individual.  However, general qualities of these different dietary approaches may be summarized in relation to their capacity to influence metabolic processes and the probable outcomes of such dietary patterns.

Dietary Fiber

Vegetarians usually have a greater in take in foods that are high in dietary fiber such as whole grains, legumes, fruit, vegetables, nuts and seeds.  A low intake of dietary fiber has been associated with a number of conditions including cardiovascular disease, diabetes, gall bladder disease, diverticular disease and bowel cancer. Omnivores generally have a lower intake of fiber and may have a potentially increased risk of developing these conditions.  A vegetarian diet may confer protection against such conditions especially if the diet limits the consumption of refined carbohydrates, as this will significantly reduce fiber intake and in addition most of the advantages of a high fiber diet are significantly reduced if refined carbohydrates contribute to >18% of energy intake.

A high dietary fiber intake is also associated with increased satiety and as such a vegetarian diet may assist in prevention of development of obesity. Fiber is also effective in reducing plasma cholesterol levels and specifically a high consumption of fruit, vegetables, soy and oats has been shown to exert a cholesterol reducing effect. Although it is possible for omnivores to achieve a high fiber intake it is much easier to reach these objectives with a vegetarian approach.

On the other hand, not all of the effects of a high fiber intake are beneficial.  Fiber may potentially interfere with nutrient absorption, which could possibly reduce the availability of amino acids, essential fatty acids, vitamins and minerals.  However in regard to minerals reduced availability has been demonstrated only when fiber is added to the diet supplementally and not when it is a naturally occurring component of the diet.

Saturated Fats

An omnivorous diet is associated with a higher intake of saturated fats which is linked with the development of cardiovascular disease and some cancers and current dietary recommendations are that saturated fats contribute to 10% or less of total energy. The inclusion of animal products such as beef, eggs and dairy will substantially increase the intake of saturated fats. 

It is entirely possible for a lacto-vegetarian or lacto-ovo vegetarian to have a saturated fat intake that exceeds that of an omnivore, especially if they rely heavily on eggs and/or dairy as a major component of the diet.  However, vegans or vegetarians that consume only small quantities of eggs or dairy products will in most cases have a very low saturated fat intake.

Total fat intake will similarly be reduced in a vegetarian diet however this will vary greatly among individuals. 

Essential Fatty Acids

Vegetarian diets are also generally higher in essential fatty acids however in vegetarians with a deficiency of nutrient cofactors required for the conversion of essential fatty acids into prostaglandin precursors, there may be an inability to efficiently utilize these fatty acids for eicosanoid production. 

In these situations an omnivorous diet can be advantageous because the inclusion of fish provides a source of the omega 3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which reduces the need for metabolic conversion of alpha-linoleic acid to EPA prior to production of the series 3 prostaglandins.

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