Should you take a vitamin B12 supplement?

You may need a little or a lot of B₁₂, but it’s worth investigating.

Annie Oakley, the larger-than-life sharpshooter and star of Buffalo Bill’s Wild West Show, was cut down by an invisible foe: a deadly form of anemia caused by a lack of vitamin B₁₂.

Back in Annie’s day, we didn’t know B₁₂ existed or that deficiency could lead to dangerous consequences (for Annie, it was death in 1926). It wasn’t until later in the 20th century that scientists discovered B₁₂ and how to use it as a treatment.

Today, B₁₂ supplements are available at every drugstore and supermarket. They’re promoted for warding off deadly anemia as well as neuropathy, memory loss, depression, and more. Should you consider taking them?

An essential vitamin

B₁₂ (also known as cobalamin) is essential for keeping your brain and nerves healthy and for making DNA and red blood cells. B₁₂ also helps lower levels of homocysteine, an amino acid linked (in high levels) to dementia, heart disease, stroke, and osteoporosis.

We typically get B₁₂ through diet. Rich sources include beef, liver, clams, poultry, fish, fortified cereals, eggs, cheese, yogurt, milk, and fortified plant milks (like soy, almond, or rice milks). For us to digest B₁₂, we first have to shake it loose from these foods.

Stomach acid helps do that. The freed-up vitamin then binds to a protein (intrinsic factor, produced by cells in the stomach lining) and makes its way to the small intestine, where it’s absorbed into the bloodstream.

B₁₂ deficiency

An estimated 3.2% of adults ages 50 or older have very low B₁₂ levels, and up to 20% may have borderline deficiency. Aging is often the cause. "We tend to produce less stomach acid as we get older. That makes it harder to extract B₁₂ from food," says Dr. Meir Stampfer, a professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health.

Other causes of B₁₂ deficiency include

• taking heartburn medications that suppress stomach acid
• eating a diet that does not include animal products
• weight loss surgery
• autoimmune diseases that attack the stomach lining or gastrointestinal tract.

How can you tell if you’re low in B₁₂? "The first signs of deficiency can be present but so subtle that they are not recognized," Dr. Stampfer says. For example, you may have muscle weakness that you chalk up to other causes.

Symptoms of full-blown B₁₂ deficiency include

• balance problems
• depression
• extreme fatigue or muscle weakness
• memory loss or confusion
• numbness or tingling in the hands and legs (due to nerve damage)
• anemia.

Should you get checked?

Checking B₁₂ levels in the blood is not routine, but it may be a good idea in our older years. "I usually check patients starting at age 65. After that, I’ll check every three or four years," says Dr. Suzanne Salamon, associate chief of gerontology at Harvard-affiliated Beth Israel Deaconess Medical Center.

Blood tests look for markers of anemia, low levels of B₁₂, and high levels of homocysteine and methylmalonic acid (MMA). "MMA is the best indicator of deficiency," Dr. Stampfer says.

Treatment

Treating B₁₂ deficiency could be as simple as eating more B₁₂-rich foods or avoiding heartburn medication. Or you may need a B₁₂ supplement. "I may recommend an over-the-counter B₁₂ pill of 1,000 micrograms daily if B₁₂ is borderline low or MMA is borderline high. After the level is back to the normal range, I will often decrease the dosage," Dr. Salamon says.

If you take a B₁₂ pill, Dr. Stampfer recommends taking the natural form (methylcobalamin), not the synthetic form (cyanocobalamin). "Studies suggest cyanocobalamin may impair kidney function in people with borderline kidney problems, so it’s better to stay on the safe side," he says.

What if you have reduced stomach acid? "In supplement form, B₁₂ isn’t bound to the food, so you don’t need stomach acid to extract it," Dr. Stampfer notes.

Annie Oakley suffered from a rare condition called pernicious anemia. In this condition, people don’t make enough intrinsic factor and therefore have great trouble absorbing any B₁₂ from the intestine. For people with this problem, B₁₂ pills may not work, and injections of B₁₂ may be required.

Is a supplement warranted if you’re not deficient? "It surely is if you don’t eat animal products," Dr. Stampfer says, "and it’s a good idea for all older individuals. Deficiency can be prevented at a very low cost and low hassle by taking a multivitamin with the average daily recommended amount of 2.8 micrograms of B₁₂."

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