Vitamins and minerals
A well-planned vegetarian meal plan is adequate in most essential vitamins and minerals. The one possible exception is vitamin B12, which occurs naturally only in animal products, including fish, meat, poultry, eggs, milk, and milk products. Vitamin B12 is essential for red blood cell formation and for proper nervous system function. Vegans, who consume no animal products, therefore need to include foods fortified with vitamin B12 in their diets or take B12 supplements. Examples of foods that may be fortified with B12 include some brands of soy beverages, breakfast cereals, veggie burgers, and nutritional yeast.
Vitamin B12 deficiency is usually caused by a low intake of foods containing vitamin B12 or by an inability to absorb the vitamin from food. Malabsorption of vitamin B12 is common among adults over 80. Pernicious anemia and a variety of gastrointestinal disorders can also cause vitamin B12 deficiency due to malabsorption.
Several minerals also merit discussion when planning a vegetarian meal plan:
Calcium. Calcium is needed for healthy bones, muscle contractions, heart action, nervous system maintenance, and normal blood. Although many people associate calcium with dairy products, it is present in a wide range of foods, including certain green vegetables (particularly bok choy, broccoli, collards, Chinese cabbage, kale, mustard greens, and okra), nuts and seeds, dried fruit, and tofu. Calcium-fortified soy beverages and orange juice can provide as much calcium per serving as cow’s milk.
Iron. Iron is needed to form hemoglobin, a protein carried by the red blood cells that transports oxygen from the lungs to the rest of the body. The iron found in meat, fish, and poultry is more easily absorbed by the body than the iron in plant foods. However, there are two ways to increase the body’s absorption of the iron in plant foods: One is to consume small amounts of meat, fish, or poultry along with plant foods — an option for flexitarians. The other is to eat foods high in vitamin C (such as bell peppers, broccoli, cabbage, cauliflower, citrus fruits, mustard greens, strawberries, and tomatoes) along with plant sources of iron, which include fruits, vegetables, dried beans, nuts, and grain products.
Zinc. Zinc plays a role in growth and development, helps the immune system function properly, and is required for proper sense of taste and smell. The zinc in animal foods is more readily absorbed than the zinc in plant foods, but certain plant foods are still considered good sources of zinc. Those include nuts, pumpkin and sesame seeds, whole grains, green peas, and dried beans and legumes. Dairy products also contain zinc, and oysters, crab, and lobster are high in zinc.
What studies show
A few research studies have examined whether following a vegetarian meal plan may help to prevent or control Type 2 diabetes. One study, published in May 2009, followed 22,434 men and 38,469 women for several years. All of the study subjects were members of the Seventh-Day Adventist church, which encourages following a lacto-ovo vegetarian meal plan, and all filled out questionnaires stating how often they ate certain foods or food groups. They were then categorized as vegans, lacto-ovo vegetarians, pesco-vegetarians (if they ate fish), semi-vegetarians, or nonvegetarians. The study results showed that all of the vegetarian groups had a lower body-mass index (BMI) and a lower risk of developing Type 2 diabetes than the nonvegetarians. Vegans and lacto-ovo vegetarians had nearly a 50% reduction in the risk of developing Type 2 diabetes.
Another study, published in 2006, looked at whether a low-fat vegan meal plan could improve blood glucose levels and cardiovascular risk factors in people with Type 2 diabetes. In the study, 99 people with Type 2 diabetes were assigned to follow either a low-fat, vegan meal plan for 22 weeks, or a meal plan that adhered to the 2003 ADA guidelines. (The ADA periodically reviews its dietary guidelines and has updated them since 2003.) No meals were provided to either group, and participants were asked not to change their exercise habits during the study.