Vitamin B12 is vital to life and health and to almost every cell and system, including the blood and the nervous system. Recent studies have found that consuming adequate amounts of B12 and other B vitamins such as folic acid (folate) and B6 is crucial in keeping the aging brain healthy, and some suggest that higher doses can help prevent age-related brain shrinkage and cognitive impairment.
The liver can store large amounts of vitamin B12, and even if you stopped consuming it altogether, you would not become deficient for months or even years. But 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 affect the ability to absorb the vitamin. Notably, 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. The vitamin is found naturally only in animal products, so vegans can be deficient unless they eat fortified vegetarian 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, or diabetes (such as metformin). Long-term use of proton pump inhibitors for reflux disease (such as Nexium and Prilosec) can also reduce B12 absorption. All these people may gradually develop the common form of B12 deficiency. There is also a less common and more serious form, known as pernicious anemia (see box below).
Avoiding misdiagnosis of vitamin deficiency
There’s controversy about routine testing for vitamin B12 deficiency and about the best way to assess B12 status. In its early stages, deficiency may have no symptoms or only subtle ones. But moderate to severe deficiency can cause diverse problems, including:
- memory loss
- 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 health care provider about symptoms like these, especially if dementia is suspected, make sure you’re tested for vitamin B12 deficiency. Blood tests can diagnose deficiency, and levels of the vitamin can be raised in various ways—pills, nasal sprays and gels, and injections.
What to do if you’re over 50
The amount of vitamin B12 needed to stay healthy is very small—the recommended dietary allowance, or RDA, is 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 at least 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 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.
Thus, the Institute of Medicine (which devises recommended nutrient intakes for the U.S. and Canadian governments, among other tasks) advises people over 50 to get at least some of their daily B12 from supplements and/or fortified foods. Most multivitamins have at least 6 micrograms; “senior” formulas often have 25 micrograms.
Vitamin B12 is available in sublingual (“under the tongue”) preparations that are supposed to be better absorbed. There’s no evidence these are preferable to regular capsules and tablets, however.
Bottom line: Most people over 50 don’t have to worry about vitamin B12 if they eat some animal products or 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 a more severe deficiency, your doctor 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 are generally reserved for certain cases of pernicious anemia and other disorders that prevent B12 absorption. Pills, of course, are easier to take.
But don’t take such large doses unless you’ve been diagnosed as being deficient, especially since the long-term risks are not known. For instance, a few studies have found that high blood levels or intakes of B12 (sometimes taken with folic acid) are associated with increased cancer risk.