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Health Options
Question: You recommend 500 to 1000 mcg of supplemental vitamin B-12 for those over age 60 who eat mostly vegetable protein. That's an amazing 8,333 to 16,666 percent of the Daily Value of 6 mcg. Does any research support the intake of such megadoses? In contrast, Consumer Reports on Health (June 2000, page 7) recommends 3 to 6 mcg of supplemental vitamin B-12 for anyone over age 50. Do you think this is enough for an age group that may not absorb B-12 adequately? -- Karen Essene, Honolulu. Building up B-12 reserves
Answer: The Consumer Reports on Health recommendation of 3 to 6 mcg/day of B-12 is a common recommendation. The current adult Recommended Dietary Allowance is set at 2.4 mcg/day. So their recommendation is plenty for normal healthy people over age 50.
Our recommendation is not based on the needs of normal healthy people. It is based on recent studies estimating that about one out of seven people over 65 years of age may lose their ability to absorb B-12 adequately. When this happens, it can take years to become deficient as the B-12 stored in the liver is steadily depleted.
When B-12 deficiency progresses undetected, it destroys lives. Mental and physical functions and the psychological and emotional state of a person decline to the point that they require a great deal of care like those with Alzheimer's disease. A part of that person is lost -- for themselves and for their loved ones. If an aging person is destined to be the one out of seven people that will develop serious malabsorption problems, then higher levels of intake in advance can be good insurance for prevention.
The usual treatment for someone diagnosed with B-12 malabsorption is to give monthly injections of 1000 mcg of the vitamin. Normal people absorb about 50 percent of the B-12 in food. In contrast, only about 1 percent of B-12 is absorbed in people with malabsorption. So, injections are needed or an oral dose great enough that 1 percent is a significant amount.
Within the last three years, two studies reported success in treating B-12 deficient individuals with oral megadoses of 2000 mcg of B-12 per day. One of these studies found that oral supplementation was as effective as injections. By the way, there is no evidence that the expensive "sublingual" types of B-12 supplements are absorbed through the mouth.
We might make a different recommendation if assessment of B-12 status was part of yearly medical check-ups. B-12 problems in older people are yet to be taken seriously by most physicians and medical centers. Complicating matters further, the usual test for B-12 status (plasma B-12) is not very reliable. Some people with plasma B-12 levels well above the clinical cutoff for deficiency are actually deficient based on other tests, symptoms, and their response to B-12 therapy.
So, until checking B-12 status becomes routine and tests get better, we recommend entering your later years with a good supply of B-12 in your liver.
For all other nutrients, we do not recommend this approach due to risks of toxicity. However, the risk of high dose B-12 is so low that the Food and Nutrition Board was unable to establish a "Tolerable Upper Intake Level" for it. The potential for benefit is so great that we think it overshadows any potential risk of high doses.
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Joannie Dobbs, Ph.D., C.N.S., is a food and nutrition consultant
and owner of Exploring New Concepts, a nutritional consulting firm.
She is also responsible for the nutritional analyses
indicated by an asterisk in this section.Alan Titchenal, Ph.D., C.N.S., is a sports nutritionist in the
Department of Human Nutrition, Food and Animal Science,
University of Hawaii-Manoa.