& Joannie Dobbs Wednesday,
Dietary B-12 may
not be enough
A high-quality lifestyle after age 65 requires staying physically active and mentally sharp. In our Sept. 13 column we described a common cause of rapid mental decline in older people -- vitamin B-12 deficiency.
With a B-12 deficiency a host of nervous system problems can develop including depression and memory loss. Although these symptoms can be related to many other causes, the nearly 15 percent incidence of B-12 deficiency in people over 65 should encourage a pro-active approach toward B-12 health. When deficiency hits, it can be devastating to the individual and their family if it is not diagnosed and treated quickly.
Most Americans consume plenty of B-12 in meat, poultry, fish, eggs and milk products. B-12 deficiency commonly stems from a reduced ability to absorb it from food. B-12 in foods is tightly bound to protein. Normal stomach acid and enzyme levels are needed to make B-12 available for absorption.
Many older people experience a decline in the secretion of stomach acids. Also, many drugs or antacids taken for stomach problems interfere with the function of stomach acid, further impairing the release of B-12 from food.
BECAUSE 10 to 30 percent of older people do not absorb B-12 from foods, the Institute of Medicine recommends that people over 50 meet their B-12 needs by consuming foods fortified with the vitamin or by taking supplemental B-12. In these forms, the vitamin is not bound to protein, so its absorption is not impaired by low stomach acid production.
A small percentage of those with B-12 deficiency have a condition called pernicious anemia. With this condition, they can't absorb B-12 even from supplement sources. The usual treatment is monthly injections of B-12 for the remainder of the person's life.
Historically, pernicious anemia was diagnosed by the presence of enlarged red blood cells. Today, this test is not reliable because a high intake of folic acid prevents the cell enlargement and many food products are now being enriched and fortified with the vitamin.
Diagnosis of B-12 deficiency is not straightforward. Some people have low serum B-12 levels with no symptoms of deficiency. Others have normal B-12 values but have the symptoms of deficiency. Consequently, to confirm a diagnosis, blood tests may be run for other substances that change when B-12 function is limited. The two most commonly measured include serum methylmalonic acid and homocysteine.
When a person has too little B-12 in their diet, it can take years for serious problems to develop because significant amounts of B-12 are stored in the liver. So B-12 deficiency proceeds to erode nervous tissue until irreversible damage is done and the result can mimic Alzheimer's disease. Dr. Sally Stabler, a B-12 authority from the University of Colorado Health Sciences Center, recommends that everyone over 65 be screened regularly for B-12 status.
Typical multiple vitamin supplements containing 100 percent RDA levels of B-12 are not adequate in people destined for the problem. A few recent studies indicate taking 1,000 to 2,000 micrograms of oral supplement daily can restore normal vitamin status in some deficient people. Whether oral B-12 can work as effectively as monthly B-12 injections in those with pernicious anemia remains to be proved.
Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S.
are nutritionists in the Department of Human Nutrition, Food and Animal Sciences,
College of Tropical Agriculture and Human Resources, UH-Manoa.
Dr. Dobbs also works with the University Health Service
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