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The number of vegetarians and vegans with vitamin B12 deficiency is very high

July 5, 2013

The majority of people following a vegetarian or vegan diet develops vitamin B12 deficiency, a situation which could be prevented by a daily supplementation of at least 250 micrograms, suggests a new US review.

The review included 18 studies from Europe, America, Africa and Asia that reported B12 deficiency rates among vegetarians and vegans (1). The data analysis showed high deficiency rates among specific popu-lations of vegetarians and vegans: 62% among pregnant women, between 25% and almost 86% among children, 21–41% among adolescents and 11–90% among the elderly. Higher rates of deficiency were reported among vegans compared with vegetarians and among individuals who had adhered to a vegetarian diet since birth compared with those who had adopted such a diet later in life. Vegetarians developed B12 depletion or deficiency regardless of demographic characteristics, place of residency, age, or type of vege-tarian diet.

The researchers commented that health professionals should alert vegetarians about the risk of developing a subnormal B12 status. Vegetarians should also take preventive measures to ensure adequate intake, inclu-ding the regular intake of vitamin B12 supplements to prevent deficiency. Considering the low absorption rate of the vitamin from supplements, a dose of at least 250 micrograms should be ingested for optimal results (2). However, many vegetarians, for various reasons, refuse to take vitamin B12 supplements. This
is largely due to various misconceptions, including the belief that it takes many years for vitamin B12 deficiency to develop. This belief is founded on the presumption that most people have adequate stores of the vitamin; however, this is very unlikely, especially in long-term vegetarians and vegans, the scientists noted.

The US Institute of Medicine’s recommended dietary allowance (RDA) of vitamin B12 needed to meet an adult’s requirement as 2.4 mg per day. Vitamin B12 is synthesized only by microorganisms, and this is why natural food sources of the vitamin are limited to meats and foods of animal origin. The vegetarian sources of vitamin B12 include milk, which contains between 0.3 and 0.4 µg vitamin B12 per 100 g, with an absorp-tion rate of about 65%. In the United States, many commercial food products are fortified with vitamin B12, including a variety of breakfast cereals, soy milk, and certain soy meat analogs. Pharmacies and health food stores offer supplements that vitamin B12 containing, mostly in the form of cyanocobalamin.