Nutritional Requirements of Vegetarians

A talk given by Robert I-San Lin, Ph.D., CNS, FICN
Although vegetarian diets can provide many health benefits, some of these diets may enhance the risk of certain nutritional deficiencies. Most plant derived foods do not contain vitamin B12 and are low in methionine, iron, zinc, vitamin A, and vitamin B6. These deficiencies are particularly damaging during the periods of rapid growth and physiological stress, such as the neonatal period throughout adolescent growth spur, pregnancy, nursing, older age, and various wasting diseases.
Vitamin B12 is synthesized by bacteria, many unicellular fungi and algae, but not by animals and higher plants. In the body, vitamin B12 serves as a methyl acceptor in the formation of tetrahydrofolate (THF) and as a methyl donor in the formation of methionine. Vegans are particularly at risk of developing neurological damage from B12 deficiency, because many vegetarian diets have a high folic acid content, which can mitigate the anemic development but let the less noticeable neurological damage to proceed. To prevent vitamin B12 deficiency, vegans must consume adequate amounts of a variety of fungi, algae, fermented foods, or a well-formulated multivitamin-mineral supplement.
Vegans are also at higher risk of vitamin A deficiency. Leafy vegetables contain abundant amounts of provitamins A, e.g., beta-carotene. Consumption of beta-carotene-rich vegetables can provide the body with the needed vitamin A. Some individuals with adequate intake of beta-carotene experienced vitamin A deficiency because consumption of insufficient amount of fat together with carotene-rich vegetables, and dietary deficiencies in iron and zinc. Thus, vegetarians are urged to consume dark colored leafy vegetables with some fat, also inactivated yeasts, spices, peas, malt extract, cocoa, and certain iron-rich leafy vegetables. Many seeds and nuts are good sources of zinc and it is advisable for vegetarians, especially, almond, peanut, cashew nut, brazil nut, pecans, pumpkin and squash seeds, sesame seeds, millet. These help prevent a deficiency of vitamin A, iron, and zinc.
On the average, vegetarian children tend to grow and develop more slowly than non-vegetarian children, and vegetarians adults tend to have slightly smaller body sizes than non-vegetarian adults. The contributed factors include the intake of calories, zinc, iron, methionine, lysine, arachidonic acid, calcium, and phosphorous. Increasing the intake of these nutrients during early childhood and through out the growth period may enhance the rate of growth and promote a larger body size. However, faster growth and a larger body size do not necessarily means better for health and longevity.
With increasing consumption of omega-6 fatty acid-rich and hydrogenated vegetable oils, vegetarians face a risk of deficiency in omega-3 fatty acids, particularly eicosapentaenoic and docosahexaenoic acids, which are important to the structure of nerve cells and hemostasis. These problems will be discussed.
Dr. Robert I. Lin has been Executive Vice President of Nutritional International Company since 1989, in charge of nutritional product research, production technology development, and clinical research. Dr.Lin is a well-respected nutritionist and leading scientist. He studied biophysics and nuclear medicine at the University of California, Los Angeles (UCLA). His post doctoral training is in nutrition, metabolic diseases, and genetic engineering/biotechnology. During the past 3 decades, he has conducted research and lectured on health-promotion and disease-prevention. His research interest is mainly in the fields of nutrition and degenerative diseases, prevention and treatment of obesity, and sports nutrition.
Robert I-San Lin, Ph.D., CNS, FICN
Nutrition International Company
P.O. Box 50632, Irvine, CA 92619-0632, USA
Fax 949-8546170, Email: