People opt for vegetarian diets both for ethical and health reasons. The two main types of vegetarian diets are the ovo-lacto vegetarians, who do not consume meat or seafood or products containing these foods but consume eggs and dairy; and vegans, who exclude all animal foods from their diets including milk and eggs. The American Dietetic Association states that appropriately planned vegetarian diets including vegan diets, are nutritionally adequate. However, unless well-planned, vegetarian diets tend to be low in iron, zinc and vitamin D, while vegan diets will also be low in iodine, calcium and vitamin B-12.
Iron
Iron is essential for the production of red blood cells, and its deficiency causes anemia characterized by fatigue, lack of concentration, irritability and an increased susceptibility to infection. Iron from plant foods, termed as nonheme iron, is less well absorbed than iron from meat, termed as heme iron. Because of this, the recommended daily intake for vegetarians is 1.8 times that of omnivores. The absorption of nonheme iron is enhanced by vitamin C found in fruits and vegetables while calcium and polyphenolics in tea and coffee inhibit absorption. Good sources of iron for vegetarians include fortified breakfast cereals, soybeans, lentils, beans -- especially kidney, lima, and navy -- tofu, spinach, raisins and whole wheat bread.
Zinc
Many enzymes in the body require zinc to function; its deficiency results in delayed sexual maturation, skin rashes, chronic diarrhea, impaired immune system and wound healing, diminished appetite and behavioral disturbances. Zinc from plant sources is less well-absorbed than zinc from animal products, and so vegetarians will require higher amounts. Plant sources of zinc include legumes, grains, cheese, nuts, and soy products.
Vitamin D
Vitamin D is synthesized in the skin when exposed to sunlight; however, blood levels will drop during the winter months. Vitamin D is also present in a limited number of foods, mainly liver, oily fish and eggs, and so vegetarians are at higher risk of deficiency. This vitamin is essential for bone health because it regulates the levels of calcium in the blood. It is also important in nerve, muscle and immune function. The American Dietetic Association recommends that vegetarians ensure adequate sun exposure, consume fortified foods and consider supplements.
Vegan Diets
According to the May 2009 issue of "The American Journal of Clinical Nutrition," vegan diets will additionally be at higher risk of calcium, iodine and vitamin B-12 deficiency. Calcium is mainly found in milk and dairy and is essential for healthy bones and teeth. Vegan sources include fortified soy milk, fortified breakfast cereals, broccoli, kale, sesame seeds and almonds. Iodine is usually obtained from fish and shellfish, eggs and milk in a non-vegan diet, and is important for thyroid function. Vegan sources for iodine include iodized salt, potatoes with peel and sea vegetables. Vitamin B-12 is used in red blood cell formation and in nerve function and it is found exclusively in animal products, so vegans need to rely on fortified foods and supplements.
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