What B12 is: Also called cobalamin, vitamin B12 is vital to life and health and to almost every cell and system, including the blood and the nervous system. In particular, recent studies have found that consuming adequate amounts of B12 and other B vitamins such as folate (folic acid) and B6 is crucial in keeping the aging brain healthy. Low levels of vitamin B12 (as well as folate and vitamin B6) are associated with high levels of homocysteine, an amino acid that, at elevated levels, is associated with an increased risk of heart disease and stroke and may also play a role in age-related mental decline and dementia. B12 is found naturally only in foods of animal origin; many other foods are fortified with it.
Claims, purported benefits: Prevents confusion and memory loss in older people, protects the heart and peps people up, especially when injected.
What the studies show: Getting B12 from food is a complex chemical process. For example, the stomach must secrete adequate amounts of acids plus the digestive enzyme pepsin to extract the vitamin from food. Then, in order to be absorbed, the free vitamin must combine with a protein known as “intrinsic factor,” secreted by the stomach lining.
In older people, however, this process may be incomplete: certain changes that occur in the digestive tract of older people affect the ability to absorb the vitamin. As a result, many people over 50 don’t produce enough stomach acid to adequately absorb B12. A poor diet and heavy drinking can contribute to a deficiency. Vegans can be deficient unless they eat fortified foods or nutritional yeast. Also at risk are people with diseases of the intestinal tract, those who’ve had certain types of intestinal surgery or chronic pancreatitis, and anyone taking certain drugs for gout, seizures and diabetes (such as metformin). Long-term use of proton pump inhibitors for reflux disease (such as Nexium and Prilosec) can also reduce B12 absorption.
Heart disease. Studies show that increasing intake of B vitamins can lower homocysteine levels—but in clinical trials, lowering homocysteine levels with B vitamins did not reduce the incidence of heart disease.
Cognitive decline and dementia. In recent years, some studies have suggested that higher doses of vitamin B12, folic acid and B6 can help prevent age-related brain shrinkage, memory loss, cognitive impairment and possibly dementia. For instance, a study at Oxford University in 2010 followed 168 people over 70 who had mild cognitive impairment, half of whom took high doses of B vitamins (500 micrograms of B12, 800 micrograms of folic acid and 20 milligrams of B6 a day), the other half a placebo. After two years, the vitamin takers had a 30 percent lower rate of brain atrophy than the placebo group, as seen on MRIs. Still, there’s insufficient evidence to recommend B vitamin supplements as a preventive for dementia.
Avoiding misdiagnosis. In its early stages, B12 deficiency may have no symptoms or only subtle ones. Moderate to severe deficiency can cause diverse problems, including confusion, memory loss, listlessness, depression and tingling and weakness in the limbs from nerve impairment (peripheral neuropathy). This may be misdiagnosed as dementia or other conditions. Or the person suffering from these symptoms may simply attribute them to “aging.” If you or someone in your family is consulting a doctor about symptoms like these, especially if dementia is suspected, make sure the doctor does a blood test for vitamin B12.
What to do if you’re over 50. The Recommended Dietary Allowance (RDA) for vitamin B12 is just 2.4 micrograms a day (a microgram is one-thousandth of a milligram). It’s easy to get that much from food if you eat dairy products, fish, red meats and/or fortified foods. The Daily Value, which is used on food and supplement labels, is 6 micrograms of B12 a day. Because of the decreased B12 absorption in older people, we recommend they consume 6 to 15 micrograms daily from food and, if necessary, supplements.
In supplements the vitamin is not bound, as it is when found naturally in foods, and thus is more readily absorbed, unless you have a condition such as pernicious anemia. Fortified foods, such as breakfast cereals and soy milks, also release the vitamin more easily because it is simply added to the foods, not bound with food molecules. That’s why the Institute of Medicine (which devises recommended nutrient intakes in the U.S. and Canada) advises people over 50 to get at least some of their B12 from supplements and/or fortified foods. Most multivitamins have at least 6 micrograms; “senior” formulas often have 25 micrograms.
Pernicious anemia. About two percent of people develop the vitamin B12 deficiency disease called pernicious anemia. Here, the stomach nearly ceases production of acids and intrinsic factor (a protein needed for B12 absorption). The result: orally consumed B12 is largely unable to be absorbed. Symptoms of the deficiency, such as severe fatigue and disorientation, may not be seen for five years or more—it can take the body that long to use up stored amounts of the nutrient. The deficiency may cause neurological damage that cannot be reversed, so it's essential to see a doctor in a timely manner. Pernicious anemia requires treatment with vitamin B12.
Bottom line: Most people over 50 needn’t worry about vitamin B12 if they eat some animal products and fortified foods and/or take a multivitamin. If you have any of the symptoms mentioned above, consult your doctor. If you do have a mild deficiency, supplements of 50 micrograms daily may be enough to correct it. For more severe deficiency, your physician may prescribe very high doses, as much as 1 or even 2 milligrams daily (that is, 1,000 to 2,000 micrograms), about 400 to 800 times the RDA. These amounts are as effective as injections, which have fallen out of favor, except to treat some cases of pernicious anemia and other disorders that prevent B12 absorption. But don’t take such large doses unless your doctor has diagnosed a deficiency, especially since the long-term risks are not known.