Vitamin B12 deficiency can be sneaky, harmful

POSTED JANUARY 10, 2013, 10:03 AM

P.J. Skerrett, Managing Editor, Harvard Health

What harm can having too little of a vitamin do? Consider this: Over the course of two months, a 62-year-old man developed numbness and a “pins and needles” sensation in his hands, had trouble walking, experienced severe joint pain, began turning yellow, and became progressively short of breath. The cause was lack of vitamin B₁₂ in his bloodstream, according to a case report from Harvard-affiliated Massachusetts General Hospital published in The New England Journal of Medicine. It could have been worse—a severe vitamin B₁₂ deficiency can lead to deep depression, paranoia and delusions, memory loss, incontinence, loss of taste and smell, and more, according to another article in today’s New England Journal.

The human body needs vitamin B₁₂ to make red blood cells, nerves, DNA, and carry out other functions. The average adult should get 2.4 micrograms a day. Like most vitamins, B₁₂ can’t be made by the body . Instead, it must be gotten from food or supplements.

And therein lies the problem: Some people don’t consume enough vitamin B₁₂ to meet their needs, while others can’t absorb enough, no matter how much they take in. As a result, vitamin B₁₂ deficiency is relatively common, especially among older people. The National Health and Nutrition Examination Survey estimated that 3.2% of adults over age 50 have a seriously low B₁₂ level, and up to 20% may have a borderline deficiency.

Are you at risk?

There are many causes for vitamin B₁₂ deficiency. Surprisingly, two of them are practices often undertaken to improve health: a vegetarian diet and weight-loss surgery.

Plants don’t make vitamin B₁₂. The only foods that deliver it are meat, eggs, poultry, dairy products, and other foods from animals. Strict vegetarians and vegans are at high risk for developing a B₁₂ deficiency if they don’t eat grains that have been fortified with the vitamin or take a vitamin supplement. People who have stomach stapling or other form of weight-loss surgery are also more likely to be low in vitamin B₁₂ because the operation interferes with the body’s ability to extract vitamin B₁₂ from food.

Conditions that interfere with food absorption, such celiac or Crohn’s disease, can cause B₁₂ trouble. So can the use of commonly prescribed heartburn drugs, which reduce acid production in the stomach (acid is needed to absorb vitamin B₁₂). The condition is more likely to occur in older people due to the cutback in stomach acid production that often occurs with aging.

Recognizing a B₁₂ deficiency

Vitamin B₁₂ deficiency can be slow to develop, causing symptoms to appear gradually and intensify over time. It can also come on relatively quickly. Given the array of symptoms it can cause, the condition can be overlooked or confused with something else. Symptoms may include:

• strange sensations, numbness, or tingling in the hands, legs, or feet
• difficulty walking (staggering, balance problems)
• anemia
• a swollen, inflamed tongue
• yellowed skin (jaundice)
• difficulty thinking and reasoning (cognitive difficulties), or memory loss
• paranoia or hallucinations
• weakness
• fatigue

While an experienced physician may be able to detect a vitamin B₁₂ deficiency with a good interview and physical exam, a blood test is needed to confirm the condition. (Vitamin B₁₂ deficiency is so easily overlooked that the Centers for Disease Control has a course for physicians called “Why Vitamin B₁₂ Deficiency Should Be on Your Radar Screen.”)

Early detection and treatment is important. “If left untreated, the deficiency can cause severe neurologic problems and blood diseases,” says Dr. Bruce Bistrian, chief of clinical nutrition at Harvard-affiliated Beth Israel Deaconess Medical Center.

B proactive

It’s a good idea to ask your doctor about having your B₁₂ level checked if you:

• are over 50 years old
• take a proton-pump inhibitor (such as Nexium or Prevacid) or H2 blocker (such as Pepcid or Zantac)
• take metformin (a diabetes drug)
• are a strict vegetarian
• have had weight-loss surgery or have a condition that interferes with the absorption of food

A serious vitamin B₁₂ deficiency can be corrected two ways: weekly shots of vitamin B₁₂or daily high-dose B₁₂ pills. A mild B₁₂ deficiency can be corrected with a standard multivitamin.

In many people, a vitamin B₁₂ deficiency can be prevented. If you are a strict vegetarian or vegan, it’s important to eat breads, cereals, or other grains that have been fortified with vitamin B₁₂, or take a daily supplement. A standard multivitamin delivers 6 micrograms, more than enough to cover the average body’s daily need.

If you are over age 50, the Institute of Medicine recommends that you get extra B₁₂ from a supplement, since you may not be able to absorb enough of the vitamin through foods. A standard multivitamin should do the trick.

Not a cure

The Internet is full of articles lauding the use of vitamin B₁₂ to prevent Alzheimer’s disease, heart disease, and other chronic conditions or reverse infertility, fatigue, eczema, and a long list of other health problems. Most are based on poor or faulty evidence.

Take Alzhemier’s disease as an example. “Although there is a relationship between low vitamin B₁₂ levels and cognitive decline, clinical studies—including those involving people with Alzheimer’s disease—have not shown improvement in cognitive function, even doses of the vitamin as high as 1000 micrograms,” says Dr. Bistrian.

For now, it’s best to get enough vitamin B₁₂ to prevent a deficiency, and not look to it as a remedy for what ails you.