Healthy vegetarian diets contain foods that are generally consumed with a greater frequency compared to a normal mixed diet. Some of these foods are of interest as they may explain differences in the rates of certain disease between vegetarian and non-vegetarian individuals. In particular, healthy vegetarian diets have been shown to be high in fruits and vegetables, whole grains, nuts, legumes and dietary fibre. The result is that those consuming a healthy vegetarian diet are likely to have higher intakes of plant based nutrients which may include antioxidant nutrients, polyunsaturated fats and other phytochemicals. The benefits of vegetarian diets are however controversial, and the evidence associating them with reduced mortality is equivocal. This may be due to the fact that although vegetarian diets contain high amounts of certain foods that may show health benefits, they are often low in others.
Some evidence suggests that platelet aggregation is lower in non-vegetarians compared to those following a vegetarian diet. This may be explained by the absence of long-chain fatty acids from fish in vegetarian diets. Both eicosapentanoic acid (EPA, C20:5 (n-3)) and docosahexanoic acid (DHA, C22:6 (n-3)) have been shown to have regulatory effects on eicosanoid formation. One effect widely reported in the literature being a reduction in platelet aggregation due to incorporation of EPA and DHA in phospholipid membranes. Although vegetarians can synthesise EPA and DHA from the omega-3 fatty acid α-linolenic acid (ALA, C18:3 (n-3)), the conversion is not efficient in most individuals due to a genetic defect in one or more of the desaturase enzymes. Vegetarians are therefore unlikely to benefit from this health effect attributed to fatty fish consumption, unless they supplement with a source of preformed long-chain fatty acids, such as docosahexanoic acid from krill.
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