NutritioN aNd HealtH iNfo SHeet Vegetarian Diets

Author(s): Cena, Emily R; Heneman, Karrie; Zidenberg-Cherr, Sheri | Abstract: A vegetarian diet can provide all the nutrients your body requires, but if you are new to vegetarianism you may have to take extra care in planning your meals. This short publication will help you make good, informed choices.

Vegetarian diets can supply adequate protein, provided that rich protein sources are included, such as beans and nuts, and higher-protein grains such as quinoa. Animal sources of protein are more easily digested than plant sources, so a vegan diet may have higher protein requirements than a diet that includes eggs or dairy products.

Iron
Adequate iron intake depends on both the amount of dietary iron consumed and the amount available for absorption. Iron absorption rates vary depending on physiological need and on the presence of other dietary components. These components can either reduce iron absorption (as with phytates and oxalates) or enhance iron absorption (as with vitamin C). Non-heme iron, the form of iron found in plants, is more sensitive to these influences than the heme iron found in animal products. Dried beans, fortified breads and cereals, spinach, chard, blackstrap molasses, bulgur, and dried fruit are good sources of non-heme iron. To improve iron absorption from these and other ironrich plant foods, consume vitamin C-rich foods at the same meal.

Calcium
For vegetarians who include dairy products in their diets, meeting calcium requirements is the same as for omnivores (individuals who eat plant and animal foods). Vegetarians and vegans who choose to avoid dairy products should take special care to consume adequate amounts of calcium from nondairy sources, such as collard PUBLICATION 8373 UNIVERSITY OF CALIFORNIA Division of Agriculture and Natural Resources greens, spinach, almonds, soybeans, and turnip greens, in addition to calcium-fortified orange juice, cereal, soy milk, and tofu. Unfortunately, substances found in some vegetables, such as oxalic acid, may reduce the body' s absorption of calcium, so individuals choosing to avoid dairy products should be sure to consume a variety of calcium-rich foods. (A list of calcium-rich foods is included in table 1.)

Zinc
Good plant sources of zinc include whole grains, nuts, and legumes; however, the zinc found in plant foods is not as well absorbed as the zinc in meat because phytates in plants bind to zinc. Vegetarian children, especially vegans, are more vulnerable to zinc deficiency than are adults, presumably because of the high zinc levels required for growth. Ample intake of legumes and whole grains may provide adequate zinc, but vegan children (and adults) should be aware of the possibility of zinc deficiency. Compared to vegans, vegetarians who eat eggs or dairy products are less likely to be deficient in this mineral.

Vitamin B12
Because vitamin B12 is found in all animal products, a dietary pattern that includes foods such as dairy products or eggs is likely to be sufficient in vitamin B12. Plants do not provide active vitamin B12, making it essential for vegans to include a reliable source of this vitamin in their diets. Research has shown an association in vegetarians between low levels of vitamin B12 and elevated levels of homocysteine, a marker of cardiovascular disease, suggesting that vegetarians should be careful to consume adequate amounts of this nutrient as well (4). Elderly vegetarians are especially prone to vitamin B12 deficiency, because the body' s ability to absorb this vitamin tends to decline with age. The active form of the vitamin (cyanocobalamin) is found in vitamin supplements and fortified foods, such as some commercial breakfast cereals, soy beverages, and certain brands of nutritional yeast. Be sure to check the label to determine whether these items contain vitamin B12. Spirulina, seaweed, tempeh, and other fermented foods are not reliable sources of the vitamin, as the form of B12 in these foods may be inactive.

Vitamin D
This vitamin is synthesized by the body upon exposure to sunlight, but many Americans today do not meet their vitamin D requirements with sun exposure alone. Food sources of vitamin D include vitamin D-fortified dairy products, egg yolks, liver, and fatty fish. Vegans are, therefore, particularly susceptible to vitamin D deficiency and should take special care to consume foods fortified with vitamin D, such as some breakfast cereals and certain brands of soy milk. They may also consider taking supplements that provide calcium and the active form of vitamin D (cholecalciferol) together.

Omega-3 Fatty Acids
These essential fats can be found in both plant and animal foods (including nuts, seeds, plant oils, and fish), and their consumption has been associated with a reduced risk of cardiovascular disease. A recent study found that both vegans and vegetarians, in comparison to omnivores, may consume inadequate amounts of omega-3 fatty acids (measured by omega-3 fatty acid levels in sphingolipids, phosphatidylcholine, phosphatidylserine, and phosphatidylethanolamine), thus suggesting a need for vegetarians to include rich sources of omega-3 fatty acids in their diets (5). The best plant sources of these fats are walnuts and ground flaxseeds (or flaxseed oil), but the type of omega-3 fatty acid in these foods (alpha linolenic acid) is not efficiently converted to the essential types found in fish, called EPA and DHA (eicosapentaenoic acid and docosahexaenoic acid). Individuals who follow a plant-based diet but include fish will likely consume sufficient EPA and DHA, but vegetarians who do not consume any fish should consider a supplement containing these two components.

How can vegetarians plan healthful meals?
The United States Department of Agriculture (USDA) Web site, MyPyramid.gov, provides the following recommendations for planning vegetarian meals: (3) Build meals around protein sources that are naturally low in fat, such as beans, len-• tils, and rice. Avoid overloading meals with high-fat cheeses to replace the meat. Calcium-fortified, soy-based beverages can provide calcium in amounts similar to • milk. They are usually low in fat and do not contain cholesterol. Many foods that typically contain meat or poultry can be made vegetarian.

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Eliminating the meat can increase vegetable intake and reduce saturated fat and cholesterol intake. Vegetarians can also turn to many ethnic cuisines, such as Indian, Middle Eastern, Hispanic, and Asian, for plant-based dishes that include protein in the form of beans, nuts, and higher-protein grains.
Several vegetarian food guide pyramids have been developed and may serve as helpful tools for planning a healthy vegetarian diet. One example is shown in table 1 (6). Another example, adopted by the Mayo Clinic, is available online at http://www.mayoclinic.com/health/healthy-diet/NU00190 (7). Does eating a vegetarian diet reduce the risk of diseases such as heart disease and cancer?
The appeal of vegetarian diets for many individuals lies in their potential health benefits. Research has shown that vegetarians have lower morbidity and mortality from a number of degenerative diseases, including cardiovascular disease and certain types of cancer. However, it has not yet been shown that it is the omission of meat per se that has caused these positive effects, as vegetarian diets often include an overall higher intake of fruits, vegetables, and fiber, and lower intake of total fat and saturated fat, compared with typical omnivorous diets (8). It has also been difficult to separate the beneficial effects of a vegetarian diet from those effects of commonly related lifestyle differences, such as not smoking, regular physical activity, and moderate alcohol consumption. Consuming a vegetarian diet, or even occasional meatless meals, can make it easier for an individual to meet the Dietary Guidelines for Americans 2005 recommendation to consume sufficient amounts of a variety of fruits and vegetables daily, or to meet the Dietary Approaches to Stop Hypertension (DASH) recommendation to consume 4-5 servings of nuts, seeds, and dried beans per week (9). Current research also suggests that consumption of a vegan diet, in comparison with the National Cholesterol Education Program diet, may lead to better maintenance of weight loss (10). Other organizations, such as the American Institute for Cancer Research (11), the American Heart Association (12), and the National Heart, Lung, and Blood Institute (13), also recommend consuming a diet high in fruits and vegetables. Due to their dependence upon fruits, vegetables, whole grains, legumes, nuts, and seeds, well-planned vegetarian diets are more likely to meet the current recommendations for dietary fiber intake. This, in turn, helps lower the risk for chronic disease by reducing cholesterol levels and by replacing foods high in saturated fat and cholesterol with foods rich in heart-healthy monounsaturated and polyunsaturated fats.
Are vegetarian diets safe for everyone?
As with any dietary pattern, accommodations must be made for the specific nutrient needs of infants, children, adolescents, pregnant and breast-feeding women, and the elderly. As long as a conscious effort is made to choose a variety of nutritionally adequate foods, vegetarians at any age can obtain sufficient energy and nutrients necessary for health (14). Some studies, however, suggest this may be difficult for children, who may not be able to consume sufficient food to meet nutrient needs from a vegetarian or vegan diet (15,16). Table 2 compares dietary recommendations for omnivorous children with those recommended for vegetarian children. Is it important to combine amino acid food sources in order to receive a sufficient quality of protein in the diet?
Yes, it is important to combine amino acid food sources because plant proteins other than soy are low in one or more of the essential amino acids. However, having adequate protein quality is easily accomplished by eating a variety of foods. Examples of vegetarian meals containing all the essential amino acids include a peanut butter sandwich; beans and rice; meals containing tofu or tempeh; meals containing eggs; and meals containing dairy products. Furthermore, there is no need to be sure that every meal or snack has the complete list of essential amino acids; it suffices to eat them over the course of a day (3).
What is a nutritionally adequate vegetarian diet?
To be nutritionally adequate, any dietary pattern-vegetarian or otherwise-should provide balance, variety, and moderation. Table 1 provides recommendations for adults (18 years of age and older) following a vegetarian diet. Suggested dietary patterns for children, adolescents, pregnant and lactating women (6), and vegans (17)