A vegetarian diet can potentially ward off cardiovascular disease, as it provides high antioxidant intake and is associated with a favorable blood lipid profile. While some investigators find vegetarianism protects against coronary disease, others do not agree and point out that plant-based diets may have harmful effects by depriving the body of essential micronutrients.
A recent clinical study showed that vegetarians, especially vegans, have a deficiency in vitamin B12 (cobalamin), and an increased level of homocysteine, a high risk factor for cardiovascular disease.*
Vitamin B12 is essential for metabolism, for forming red blood cells and for maintaining a healthy nervous system. B12 is needed for DNA synthesis during cell division, which is especially important in bone marrow, where red cells are formed.
Prolonged vitamin B12 deficiency, due to low intake or poor intestinal absorption, causes a slow depletion in tissues. The depletion process may take years and results in a loss of red blood cells, anemia and irreversible neurological damage. Vitamin B12 deficiency symptoms include fatigue, depression, weakness and poor memory.
The only reliable unfortified natural sources of vitamin B12 in the human diet are meat, dairy products and eggs. People who restrict their diet to plant-based foods are at risk of becoming vitamin B12 deficient.
The new study recruited 174 healthy vegetarian subjects. These included 66 lactoovovegetarians (LOV), who exclude meat, poultry and fish from their diet and lactovegetarians (LV), who further exclude eggs, as well as 29 vegans, whose diet excludes all animal-based foods. Control subjects were omnivors (79 subjects), who ate both animal and plant foods. In the study, 17 of the vegans and 12 of the LV-LOV subjects supplemented their diet with B vitamins.
The subjects were monitored for a year, after which their blood was analyzed for vitamins B12, B6 and folic acid, three nutrients that play an important role in reducing blood homocysteine. Two substances that are sensitive markers for B12 deficiency, methylmalonic acid and holotranscobalamin, were also measured. The results showed that vegetarians had different degrees of vitamin B12 deficiency, which were related to the degree of animal product restriction in the diet. Vegans had the lowest levels of B12 and the highest levels of homocysteine, as compared to the LV, LOV and omnivors. Those who took vitamins had similar levels of B12 as the omnivors. A form of anemia and relative folate shortage were linked to vitamin B12 deficiency. Homocysteine rises with advancing age, whereas vitamin B12 declines, which further increases the risk of cardiovascular disease risk, in older vegans.
The study concluded that “more emphasis should be placed on effective vitamin B12 supplementation and monitoring of vitamin B12 status, in persons who have chosen lifelong adherence to a vegetarian diet.”
— Carmia Borek, Ph.D.