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What Vegans Need to Know About B12

Vegan nutritional yeast on spaghetti

One of the most challenging nutrients to obtain from a vegan diet is Vitamin B12. Most vegans use fortified products or take a vitamin supplement. But recent news has shown some concern about long-term, high dose supplementation. Here we hope to clear things up a bit.


Vitamin B12 is a water-soluble vitamin that is required for proper red blood cell formation, neurological function and DNA synthesis. B12 is bound to protein in food, which is released during digestion by the activity of hydrochloric acid and gastric protease in the stomach. The freed vitamin then combines with intrinsic factor made by the cells in the stomach and that resulting compound is eventually absorbed into the body in the small intestine.

Thankfully, vitamin B12 is only needed in small doses by the body. In fact, only 2.4 micrograms is needed each day to meet an adult’s daily requirements.

Unfortunately, though, B-vitamin supplements are marketed to people as being necessary for energy and metabolism. They often recommend high dose products to people who may not even need them. Vegans are often among this group of targeted people.

It is true that when following a vegan diet, it is harder to obtain B12 in the diet. Animal products naturally contain B12 while plant foods do not. But vegans may be getting all they need with fortified products in a well planned diet – so the high-dose supplements may not be needed, and may in fact even be harmful.

New research from The Ohio State University Comprehensive Cancer Center has found that long-term, high dose B-vitamin supplementation – in particular B6 and B12, may increase the risk of lung cancer in men, especially those that smoke. Obviously, smoking is already a risk factor for lung cancer, but adding high dose supplements may further increase that risk by as much as four times.

The study, known as VITAL (Vitamins and Lifestyle), utilizes data from more than 77,000 patients between the ages of 50 and 76. Those taking supplements of more than 20 mg of B6 and 55 mcg of B12 each day for 10 years were found to be at increased risk.

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So, first of all – keep in mind that this is the first study to find such results. More studies are indicated to find more. For example, are the patients taking the vitamin supplements without a clear deficiency or medical reason? Older adults, such as those in the study have a higher risk of deficiency because of decreased stomach acid (as noted before, this helps break down the vitamin into its usable source).

Also note that the supplementation doses were greater than that found in your typical multivitamin, says Theodore Brasky, PhD.

If you are vegan, who eats breakfast cereals and whole grains, simply check the label of your favorite product to see if it is fortified with 100% of the daily value for B12. Check your plant milk and meat substitute as well, as some brands also fortify B12. And Bob’s Red Mill Nutritional Yeast is said to have 2 mcg per 1 Tablespoon serving.

If you find that you are not getting enough B12 from fortified foods, consider asking your doctor for a blood test to evaluate your current body stores. This is especially important if you are experiencing any unusual symtpoms such as fatigue/weakness or neurological changes such as numbness or tingling in the hands and feet or difficulty maintaining balance.

Should you need a vitamin supplement for B12 (or any vitamin or mineral), only take what you need – there is no added benefit to taking super-high doses. If a doctor finds you deficient and orders a very high dose supplement, keep in mind that this is typically for only a short time to replete body stores – the study above focuses on those who take high doses over a very long period of time (10+ years).

Journal Reference:
Theodore M. Brasky, Emily White, Chi-Ling Chen. Long-Term, Supplemental, One-Carbon Metabolism–Related Vitamin B Use in Relation to Lung Cancer Risk in the Vitamins and Lifestyle (VITAL) Cohort. Journal of Clinical Oncology, 2017; JCO.2017.72.773 DOI: 10.1200/JCO.2017.72.7735

Other Resources:
National Institutes of Health – Office of Dietary Supplements
Harvard Medical School
The Vegan Society

Photo Credit:
Wikimedia Commons