The vitamin B-12 and vegans myth can be an emotional issue. Many people make the decision to become vegan for personal and ethical reasons, and this may be largely emotional in nature. In turn, omnivores may become defensive about their dietary habits and point out the risk of B-12 deficiency as an argument against veganism. This argument has prompted some vegans to defend against the alleged nutritional pitfalls of their diet. The debate has produced confusion as to the real status of vitamin B-12 in vegan diets. The RDA for vitamin B-12 is 2.4 micrograms in adults.
Vitamin B-12 Sources
The Vegetarian Resource Group website explains that neither plants nor animals manufacture vitamin B-12; it's synthesized by bacteria. The bacteria are abundant in soil and water, and animals obtain their vitamin B-12 from foodstuff contaminated by these bacteria. Plant foods do not contain vitamin B-12 except when contaminated by the proper bacterial microorganisms. Thus plant foods do not make a reliable source of vitamin B-12. The Vegetarian Resource Group advises the prudent vegan to include B-12 sources in their diets.
Vitamin B-12 Deficiency
The May 2009 issue of "The American Journal of Clinical Nutrition" reports that vitamin B-12 deficiency can have dire consequences. They further report that vegans have a higher prevalence of deficiency than do omnivores and vegetarians. Disorders caused by deficiency include anemia, difficulty concentrating, mood swings and apathy. More serious mental disorders linked to deficiency include psychoses and dementia. Other symptoms include lightheadedness, an impaired sense of taste and smell, and abnormal gait.
Prevalence of B-12 Deficiency
The Merck Manuals Online Medical Library reports that inadequate vitamin B-12 intake is unlikely except in the case of vegans. Breastfed babies of vegan mothers are at risk of deficiency by the age of four to six months, because their liver stores are limited and their rapid growth rate carries with it a high demand for nutrient availability. The Physicians' Committee for Responsible Medicine website advises that B-12 requirements increase during pregnancy and advises pregnant vegans both to take supplements and eat B-12 fortified foods.
Yeast as a B-12 Source
Many vegans rely upon B-12-fortified yeasts for their nutritional requirements, but the Vegan Health Organization warns about potential drawbacks with this option. The primary problem is that vitamin B-12 is light-sensitive, and nutritional yeast is likely to be exposed to light because it's often stored in plastic bags or clear bins. When buying nutritional yeast from bins in health food stores, the Vegan Health web site reports that the wrong yeast can find its way into the bin. As a case in point, their website reports on one vegan who thought he was getting B-12 from nutritional yeast yet developed deficiency symptoms. Vegans are advised not to rely solely upon nutritional yeast for their vitamin B-12 requirements.
References
- The Vegetarian Resource Group: Vitamin B-12 in the Vegan Diet
- "The American Journal of Clinical Nutrition"; Health Effects of Vegan Diets; Winston Craig; May 2009
- Merck Manuals: Online Medical Library: Vitamin B-12
- Physicians' Committee for Responsible Medicine: Vegetarian Diets for Pregnancy
- Vegan Health Organization: Vegan Sources
Member Comments