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n the 1980s, many nutritionists and some physicians began to recom- mend (and take) vitamin supple-
ments. However, as described in “Cast of characters: From vitamin A to zinc,” page 16, the evidence for the health bene ts of most supplements is not strong. Notable exceptions are vitamin D for bone health and folic acid during pregnancy. Although foods that contain vitamin A and beta carotene, as well as vitamins B, C, and E, are clearly good for health, taking supplements of these vitamins has no proven health bene ts.
What about a simple multivita- min-multimineral supplement—a
product that is designed to meet the
RDAs and to compensate for dietary
shortfalls? By de nition, “multivita-
min” means the product contains more than two ingre- dients. Some multivitamins contain all of the essential vitamins and minerals, and some contain just a few of them. ere is no one formula for a multivitamin- multimineral supplement, so the components of these pills vary widely, depending on the manufacturer and intended consumer (children, adults, women, older adults, etc.) or organs of concern (the heart, the eyes), and the doses are tweaked as nutrition science evolves.
Multivitamin-multimineral supplements are the most popular among all dietary supplements—half of Americans take them on a regular basis, shelling out more than $20 billion annually on these products. On an individual basis, a daily multivitamin won’t set you back that much: a year’s supply of many popular brands costs about $30.
However, despite the widespread belief that mul- tivitamin-multimineral supplements will prevent chronic diseases such as cancer and heart disease, the U.S. Preventive Services Task Force has concluded that there is isn’t enough evidence to support such claims. e main reason for this conclusion is that only one large- scale, long-term randomized con- trolled trial—the Physicians’ Health Study II—has tested the e ects of a regular multivitamin. In that trial, which was limited to men, those who took a daily multi for over a decade had no less risk of having a heart attack or stroke or dying of cardiovascular disease than men who did not take a supplement. However, men taking a daily mul- tivitamin displayed a signi cant 8% reduction in cancer and a 9% reduc- tion in the development of cataracts. e upshot of this is that we need
more high-quality research to evaluate the bene ts of multivitamin-multimineral supplements—and a new large trial to do just that is now recruiting subjects.
e good news is that of all vitamin or mineral supplements you could take, a standard multivita- min-multimineral supplement has the fewest poten- tial downsides and the most potential benets for your health. In addition, they are already part of some ocial recommendations. e federal government’s Dietary Guidelines for Americans suggests that peo- ple older than 50 take a multivitamin-multimineral supplement as a way to ensure adequate vitamin B12 intake. And the Centers for Disease Control and Pre- vention advises all women of childbearing age to take folic acid—and a multivitamin-multimineral supple- ment is also a good way to do that—because doing so lowers the risk of birth defects (see “Folic acid,” page 19). at leaves men ages 50 and under as the only adult group not covered by this advice.
When choosing a multi, look for an inexpensive preparation from a mainstream manufacturer to ensure quality and consistency. It should contain 100% of the DV for vitamin D, vitamin B6, vitamin B12, and folic acid (see Figure 6, below). Extra vitamin D is unlikely to be harmful—as noted earlier, many experts recom- mend 1,000 IU, which is almost twice the DV and is now found in many formulations. But extra amounts of other vitamins may do more harm than good.
What about supplements aimed at women, men, and seniors? While some of these supplements may be helpful in certain cases, others are merely market- ing gimmicks designed to enhance pro ts rather than your health. Products vary widely; read the labels to make sure you get what you need while staying within safe limits for your age and gender.
Don’t waste your money on high-potency, all- natural, or designer vitamins. Above all, remember that your daily multi is at least an insurance policy—a supplement, not a substitute, for a healthful diet—that may or may not provide long-term health bene ts.
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- Đang cập nhật... n the 1980s, many nutritionists and some physicians began to recom- mend…