Are vegetarians at risk for vitamin B12 deficiency?
Vegans are at greatest risk of vitamin B12 deficiency. Animal products are the only reliable sources of vitamin B12, which is important for the nervous system and to prevent anemia. If you eat no animal foods, look for B12-fortified products such as some soy milks and breakfast cereals, and/or take a B12 supplement. Some brewer's and nutritional yeasts are fortified with B12—but not all are, so check the labels.
What other vitamins and minerals does a vegetarian need for good nutrition?
Some vegetarians may also fall short in zinc, calcium, vitamin D, and iron, depending on their diets, and should consider taking a daily multivitamin/mineral pill, as well as calcium and vitamin D supplements. Vitamin D2, as opposed to D3, always comes from non-animal sources. Zinc is found in legumes, grains, wheat germ, soy, and nuts, though it's not as well absorbed as the zinc in meat and milk. Some leafy greens (such as broccoli, collards, and kale), tofu (processed with a calcium salt), dried figs, tahini, and almonds provide calcium. If you don't consume dairy products, look for calcium-fortified beverages, such as soy milk, and other calcium-fortified foods. Some breakfast cereals, nondairy milks, and juices are also fortified with vitamin D.
Because the iron in plant foods (nonheme) is not as well absorbed as the iron in meat (heme iron), going vegetarian may mean you need to consume more iron. Vitamin C and other substances in fruits and vegetables enhance the absorption of nonheme iron, so it's a good idea to include fruits or vegetables that are rich in vitamin C with every meatless meal (eat beans with a tomato salad or glass of orange juice, for instance). Still, vegetarians do not have a higher incidence of anemia or lower iron stores than nonvegetarians. If you're pregnant and going vegetarian, talk to your doctor about whether you need any supplements.
I don't eat fish—should I take an omega-3 supplement to meet my nutritional needs?
Maybe, especially if you are pregnant or breastfeeding. Vegetarian diets supply a plant form of omega-3 fats, called alpha-linolenic acid (ALA), found in flax and hempseeds, walnuts, canola oil, and soy, as well as in some green leafy vegetables and vegetable oils. But plant sources lack eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the omega-3s found predominantly in fish, which are needed for brain development and are good for your heart. The body converts only very small amounts of ALA to EPA and DHA. ALA may have its own health benefits, but it can't substitute for EPA and DHA. Vegan omega-3 supplements supply EPA/DHA from marine algae as opposed to fish oil. You don't need supplemental ALA, as from flaxseed capsules.
Are vegetarians at higher risk for bone loss and osteoporosis?
The evidence is inconsistent. Bone density and fracture risk are affected by many dietary, lifestyle, environmental, hormonal, and genetic factors. Some studies suggest that vegans, who consume less calcium, are at higher risk of fractures. But others suggest that some things about vegetarian diets—such as phyto-estrogens from soy foods, vitamin K from fruits and vegetables, and the lower levels of acid-forming compounds in the diets—are beneficial for bones. A 2009 analysis in the American Journal of Clinical Nutrition found that vegetarians, especially vegans, have lower bone density—but the effect is so modest that it's unlikely to increase the risk of fracture.
To best protect your bones, consume adequate calcium, vitamin D, and protein after going vegetarian; do regular weight-bearing exercise; keep alcohol intake moderate; and don't smoke—the same advice nonvegetarians should follow.
Originally published in The University of California, Berkeley Wellness Letter (March 2011)