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August 29, 2005
Vitamin B-12 deficiency may be the most common nutritional deficiency in the developing world, and maybe even in the U.S.," said Lindsay Allen at the annual Stare-Hegsted Lecture in Snyder Auditorium on March 31. Allen, the director of the USDA Western Human Nutrition Research Center at the University of California, Davis, presented the lecture named for the late Fredrick Stare, the founding chair of the Department of Nutrition who died in 2002, and D. Mark Hegsted, HSPH professor emeritus.
"We once thought B-12 deficiency was rare [in most populations] because it is so efficiently reabsorbed from bile,’" she said. "For example, it takes six years to deplete your store of B-12 if it’s not in your diet. But if you start off with smaller stores, you can become depleted in less than three years."
B-12 (cobalamin), important in neurological development and function, is bound to proteins in food, especially to animal protein. Stomach acids and enzymes help separate the cobalamin from the protein, freeing the nutrient for absorption into the blood. A small amount is excreted into bile by way of the gall bladder, and then reabsorbed into the bloodstream. Bacteria and some parasites living in the digestive tract might interrupt this process. So can certain types of disorders and GI system deterioration caused by Helicobacter pylori as people age.
Popular antacids interfere with B-12 absorption because they reduce the secretion of gastric acid that is needed to release the vitamin from food.
It was commonly thought that only strict vegetarians, the elderly, and those with pernicious anemia (an autoimmune disease that causes only about two percent of the vitamin B-12 deficiency in the U.S.) had to worry about deficiency of the vitamin.
However, Allen and her team have conducted research in Guatemala, Mexico, Kenya, and the U.S. that indicates B-12 deficiency is rampant, especially among the very young and very old. The prevalence is about 40 percent in studies in Latin America, and more than 22 percent in U.S. elderly over 65 years of age. Deficiency is even more common in some African countries, India, and Nepal. No demographic group is immune. Low plasma levels of B-12 have been reported in many studies of traditional vegetarians in Europe and Australia.
One 1990 study of macrobiotic mothers in Boston showed insufficient levels of B-12 in breast milk, even in women who had followed a macrobiotic diet for as little as two to three years.
Low in utero accumulation of B-12, followed by low concentrations in breast milk, can cause deficiencies in babies in developing countries. "These babies are born without even a chance to have reasonable stores in the beginning of life," said Allen. In Guatemala, about two-thirds of infants are deficient by seven months of age. School-age children in Guatemala with long-term B-12 deficiencies experience trouble learning, perform poorly on memory, reasoning, and perception tasks, and exhibit more aggressiveness than those with adequate B-12.
People who consume little meat and do not take B-12 supplements or fortified foods are at high risk of B-12 depletion over time. Allen blamed long-term lack of B-12 for some instances of neurological damage in adults and in the elderly. If the problem is caught early enough, the damage might be reversed. But, deep myelination, or the erosion of the protective sheath around the axons of neurons, may not be reversible if B-12 deficiency is severe or long-term, she said.
People do not need to eat a lot of meat or other kinds of food from animals, such as eggs and milk, to keep B-12 levels normal, and there’s no such thing as too much B-12, said Allen. One or two ounces a day is minimally sufficient.
In a project in Kenya, children who had lacked B-12 were given meat and milk products in snacks at school for two years to bring their levels up to normal. They were also given tempeh, a vegetable product containing some useful B-12 because bacteria that live on the surface produce the nutrient, she said.
Allen acknowledged that she has been criticized by the vegan community for what they perceive as anti-vegan comments — taken out of context by the press, she said. She recommends the following remedies to counteract and prevent the serious consequences of long-term and widespread B-12 deficiency:
• Advocate the fortification of foods, especially flour, to slowly raise B-12 levels in the U.S. and in developing countries, where meat is scarce.
• Reevaluate the effect of the lacto-ovo vegetarian diet, or one that includes eggs and dairy, on plasma B-12 levels and its long-range consequences to be sure that it does not cause vitamin B-12 deficiency.
• Develop better ways to measure B-12 absorption.
• Starting at about age 55, encourage people to have their vitamin B-12 status checked. If deficient, advise them to take high-dose supplements (0.5-1 mg per day).
• Initiate more research into cause-and-effect relationships between B-12 deficiency and disease or disabling conditions, especially for infants and young children.
"If we want the FDA to fortify foods with vitamin B-12 or other nutrients, we must petition them," she added.
The lecture was sponsored by the Department of Nutrition.
--PHC
Harvard Public Health NOW is published biweekly by the
Office of Communications
Harvard School of Public Health
665 Huntington Ave., SPH 1-1312
Boston, Massachusetts 02115
617-432-6052
Editor and Layout: Christina Roache
Contributing Writer: Paula Hartman Cohen, Carol Cruzan Morton
Copyright 2005 President and Fellows of Harvard College
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