QUESTION: I watched a health report on TV that said that most older women don't get enough vitamin D. Do you agree with this report? Also, would you explain a little more about what vitamin D is used for and the best sources for it? Thank you.
ANSWER: The television report you saw may have been based on an article in the June 1990 issue of the Tufts University Diet & Nutrition Letter, which stated that many older women get much less vitamin D than they need to properly absorb calcium from the food they eat. In a study of a group of more than 300 women with an average age of 58, the average consumption was only 112 International Units - slightly more than half the recommended allowance of 200 International Units. In another study, at least half of a group of elderly people living in New Mexico were found to be consuming fewer than 50 International Units, or only one-fourth of the RDA.Three other problems could make this situation worse: First, the research from the Tufts scientists suggests that the RDA (recommended daily allowance) may be about 10 percent too low for older women. Therefore, even if they get "enough" vitamin D, according to the RDA they could still be low. Second, in addition to getting vitamin D from foods, most people get a good deal of this vitamin from its synthesis in the skin upon exposure to the sun. However, the skin of older people is less efficient at making vitamin D than the skin of young adults. To compound the problem, many older Americans do not get outdoors much and therefore are rarely in the sun. Third, laxatives, such as mineral oil, can prevent the absorption of vitamin D, and many older citizens use laxatives regularly.
The worry about too little vitamin D has to do with its role in the absorption of calcium from the foods we eat. Calcium is a critical mineral in that it is used to keep bones strong but is also required for other critical body functions such as regulation of the heart and the proper functioning of nerve tissue. When too little vitamin D is present to facilitate calcium absorption, the bones must sacrifice calcium to the blood to maintain normal body function. Of course, if bones give up their calcium to maintain the other crucial functions, their density will decrease, and the person will be more vulnerable to the problem of osteoporosis. According to this article, one out of three senior citizens with hip fractures examined at a major medical center was deficient in vitamin D.
The best low-fat source of vitamin D is skim milk. Since each cup is fortified with half the RDA, or 100 International Units, two cups a day would meet the basic requirements. If you don't like milk, make an effort to include it in soups, puddings or casseroles. Other good sources of vitamin D include sardines, salmon, herring, mackerel and swordfish. Eggs, chicken livers and some fortified cereals are decent sources, too. Of course, outdoor activity can provide some, too.
If it is impossible to get some sun, and if milk and fish are not things you like or can eat, you might ask a physician if it would be prudent for you to take a vitamin D supplement. Supplements containing 400 International Units a day - twice the RDA - are usually considered safe.