Vitamins and minerals in a vegetarian diet

Vitamins and minerals are called micronutrients, and in general vegetarians get a lot of them. A vegetarian diet has more magnesium, folic acid, and vitamins C and E than an omnivorous diet (one that includes meats). It is also high in fiber and plant nutrients such as flavonoids that are often powerful antioxidants. Nevertheless, vegetarians may not get enough of certain micronutrients:

• Iron. Even though many plant foods provide lots of iron, only animal foods have the type of iron that is easily absorbed by the gastrointestinal system—heme iron. Iron status tends to be lower in vegetarians, but supplements are only a good idea in those who have been diagnosed with iron deficiency.
• Zinc. Vegetarians get zinc from nuts and seeds, legumes, and whole grains, but much of the zinc in these foods is bound up with fibers that reduce its absorbability. Since low zinc status is common in both vegetarians and meat eaters, taking a daily multivitamin with zinc is a good idea for everyone.
• Vitamin B12. A vegan diet, which does not include dairy products or eggs, is low in vitamin B12 because B12 is found primarily in animal foods. The bacteria that live in the large intestine produce some B12, and vegans may get small amounts from bacteria on fresh foods; however, because their risk of B12 deficiency is higher than meat eaters’, the report recommends that strict vegans take extra vitamin B12.

Vegetarians are short in healthy fats

Carbohydrate, proteins, and fats are known as macronutrients. Vegetarians tend to get more fiber from complex carbohydrates than meat eaters, and a proper balance of proteins from legumes, whole grains, and nuts and seeds can provide all of the necessary amino acids. A vegetarian diet is low in harmful saturated fats, but its proportions of omega-6 and omega-3 polyunsaturated fats may be of concern.

The types of omega-3 fats that have been most heavily studied for their health benefits are those from fish, EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). The type of omega-3 fat found in vegetarian foods, including the richest sources like flax, hemp, and perilla seeds, is not easily converted to EPA and DHA. Because vegetarians have been found to have lower blood levels of omega-3 fatty acids than meat eaters, the report’s authors suggest that increasing intake of EPA and DHA might further protect vegetarians against heart disease.

Beefing up a vegetarian diet

A vegetarian diet is decidedly healthy, but this report suggests that it could be even healthier. “On the basis of the present data, it is suggested that vegetarians, especially vegans, could benefit from increased dietary intake of omega-3 polyunsaturated fatty acids and vitamin B12,” the authors of the report said.

In addition to B12 supplements, some types of nutritional yeasts are non-animal sources of B12. Vegetarians who want to increase their omega-3 fatty acids status without eating fish or taking fish-derived supplements can look for supplements made from seaweed extracts.

(J Agric Food Chem 2011;59:777–84)