Are You Low on Vitamin B12?

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By Nancy Lonsdorf, MD

Q: I’ve been a vegan for nearly 25 years and was recently diagnosed with low vitamin B12 levels. I’m being treated with B12 shots, but how can I prevent getting deficient again?

A: Vitamin B12 deficiency is a growing health problem, caused in whole or in part by vegetarian diets, antacids, diabetes medications, alcoholism, iron deficiency, aging, and digestive disorders (such as malabsorption, Crohn’s disease, and celiac disease). Recent research indicates that nearly 40 percent of adults have marginal levels of this vital nutrient and are at risk for deficiency symptoms.

Your body needs B12 to produce blood cells, replicate DNA, and form the protective sheath around nerves. Inadequate amounts of this nutrient can cause anemia and nerve damage—which manifest as memory problems, fatigue, poor concentration, depression, and numbness or tingling in the feet or hands. Such symptoms may take as long as 18 months to reverse and, indeed, may never resolve. Of more concern, perhaps, is that the risk of dementia, which already affects more than a third of octogenarians, doubles with suboptimal B12 levels.

Since only animal products (including dairy and eggs) appear to contain biologically active vitamin B12, your vegan diet most likely caused the deficiency. I recommend continuing to supplement with B12 in the future. Fortunately, recent research has found that oral supplementation with high-dose vitamin B12 (1,000 mcg a day or more while correcting a deficiency) restores normal levels just as effectively as injections. While blood levels usually normalize within one to two weeks, it takes six months or longer to replenish whole-body stores. Check with your doctor to see if getting your B12 through pill supplements rather than shots would work for you.

Although you only need 2 to 3 mcg of B12 daily, your body sometimes absorbs only 1 percent of B12 supplements. I recommend at least 500 mcg a day to ensure adequate levels. For example, vegetarians who consume three servings of dairy products a day (providing the requisite 3 mcg of B12) theoretically get enough of this nutrient. In practice, however, they’re often low because it’s not all absorbed. So have your levels checked or take supplements. Even nonvegetarians who forgo multivitamins and don’t regularly eat fortified cereal or dairy products are at risk for deficiency; they should get evaluated as well. Spirulina and a few other seaweeds offer plant sources of B12, but debate rages about whether it’s biologically active in the body. In fact, some research suggests these inactive forms of B12 may actually lower your levels of the nutrient.

3 ways to get started:
1. Eat foods high in vitamin B12, such as fortified grains and cereals (with soy milk, if vegan), meat, dairy, and eggs.

2. If you are vegan, suffer from Crohn’s disease, or have any other risk factors for B12 deficiency, consider supplementing with 500 mcg a day.

3. If you fall into the high-risk categor...

Author: Nancy Lonsdorf, MD

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