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What everyone (especially vegetarians) should know about B12 deficiency
Posted By Chris Kresser On January 18, 2013 @ 8:00 am In Food & Nutrition,Myths & Truths | 111 Comments
[1]In May of 2011, I wrote an article called B12 Deficiency: A Silent Epidemic With Serious Consequences [2]. I argued that B12 deficiency is much more common than statistics indicate, with potentially devastating consequences. B12 deficiency can cause or is associated with:
• Premature aging
• Neurological disorders similar in presentation to multiple sclerosis
• Brain fog, memory problems and cognitive decline
• Stroke, heart disease and other vascular problems (due to elevated homocysteine)
• Developmental or learning disabilities in children
• Impaired immune function, autoimmune disease and cancer
• Male and female infertility
• Numerous other symptoms…
(i.e. deficiency sets in long before obvious symptoms appear), and some of the more serious effects of B12 deficiency (such as nerve damage) are irreversible.
The effects of B12 deficiency can be irreversible—but most who are deficient don’t know it. [5]
Although rates of B12 deficiency are much higher in vegetarians and vegans than in omnivores, that doesn’t mean it’s rare in omnivores. According to the study above, approximately 1 in 20 omnivores are B12 deficient. In my practice I’d estimate the rate at closer to 1 in 15, possibly because I see a lot of people with gut problems and that is one of the risk factors for B12 deficiency. Other risk factors include age (people 60 or older), present or past use of acid-suppressing drugs or other medications like metformin and women with a history of miscarriage and infertility.
B12 is the only vitamin that contains a trace element (cobalt), which is why it’s called cobalamin. Cobalamin is produced in the gut of animals. It’s the only vitamin we can’t obtain from plants or sunlight. Plants don’t need B12 so they don’t store it. B12 is found exclusively in animal foods, such as liver, clams, oysters, mussels, fish eggs, octopus, fish, crab and lobster, beef, lamb, cheese and eggs.
A common myth amongst vegetarians and vegans is that it’s possible to get B12 from plant sources like seaweed, fermented soy, spirulina and brewers yeast. But plant foods said to contain B12 actually contain B12 analogs called cobamides that block intake of and increase the need for true B12. (9 [14]) My intention here is not to bash vegetarian and vegan diets (I was a macrobiotic vegan myself at one point, for crying out loud!). I recognize that there are many reasons why people choose to eat the way they do, and I respect people’s right to make their own choices. I also know that, like all parents, vegetarians and vegans want the best for their children. This is why it’s crucial for those that abstain from animal products to understand that there are no plant sources of B12 and that all vegans and most vegetarians should supplement. This is especially important for vegetarian or vegan children or pregnant women, whose need for B12 is even greater than adults. In addition, omnivores that are low in B12 despite eating a diet rich in animal foods that contain B12 should also supplement.
Supplementing with B12
Cyanaocobalamin is the most frequently used form of B12 supplementation in the US. But recent evidence suggests that hydroxycobalamin (frequently used in Europe) is superior to cyanocobalamin, and methylcobalamin may be superior to both – especially for neurological disease. (9 [15], 10 [16] p. 225) This is probably because methylcobalamin bypasses several problems in the B12 absorption cycle and doesn’t need to be decyanated or reduced to the (+1) state (the only state that can cross the blood-brain barrier). On top of that, methylcobalamin provides the body with methyl groups that play a role in various biological processes important to overall health.
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