Vitamin B12 Deficiency In Vegetarian Diets

October 6, 2011 | by

Jaime Scholz, MS

Vitamin B12 is an important nutrient required for growth and repair of tissue. It also helps decrease inflammation and homocysteine levels, and there is some scientific evidence that combining B12 with fish oil may help reduce total serum cholesterol and triglyceride levels.

Homocysteine generates reactive oxygen species, which increases the risk for atherosclerosis . As vegetarian diets become more restrictive, homocysteine concentrations increase, peaking in vegan groups, which may counteract the known health benefits of vegetarian diets . In addition to elevated inflammation, prolonged deficiency manifests in neurologic and gastrointestinal disorders as well as anemia2.

One of the challenges for vegetarians is to find food sources with bioavailable B12. Typically, plant sources do not contain adequate amounts of bioavailable B12, and often the only reliable source for vegetarians and vegans is dietary supplements . Plant foods with the highest bioavailable B12 are purple and green algae, which are optimal for supplementation . Though used frequently, spirulina contains large amounts of the biologically inactive B12 and is not considered a suitable source for supplementation.

For Lacto-ovo vegetarians best food sources of bioavailable B12 include dairy products (eggs, yogurt, milk), while pescatarian sources include shellfish (oyster muscle, short-necked clam) and fish meats (skipjack, yellow fin tuna, and rainbow trout) 4.

Because absorption of B12 is so variable, the best way to see if levels are adequate is through a lab draw. Patients with inadequate B12 that cannot be increased through diet alone can benefit from injectible B12. Your Cenegenics physician can help you decide if you suffer from low vitamin B12.


1. Herrmann et al.: HCY, Vitamin B12, and Antioxidant Status in Vegetarians. Clinical Chemistry 47:6; 1094-1101 (2001)

2. Mezzano el al. Vegetarians and cardiovascular risk factors: hemostasis, inflammatory markers and plasma homocysteine. Thromb Haemost 1999; 81:913-7.

3. Key T.J. Et Al. Health Effects of Vegetarian and Vegan Diets. Proceedings of the Nutrition Society (2006), 65, 35-41

4. Fumio Watanabe Review,Vitamin B12 Sources and Bioavailability. School of Agricultural, Biological and Environmental Sciences, Faculty of Agriculture, Tottori University, Tottori 680-8553, Japan