We don't have much good to say about many supplements, but here are some that we recommend for at least some groups of people.
CalciumThis mineral is essential for bone health and many bodily functions. The recommended dietary allowance (RDA) for women over 50 and men over 70 is 1,200 milligrams a day; for other adults it is 1,000 milligrams. It's best to get calcium from foods and beverages naturally rich in calcium because these supply many nutrients important for bones and general health. But for people who don't eat calcium-rich foods often, supplements are recommended.
In the past few years a few studies have suggested that calcium supplements modestly increase the risk of heart attacks, which has led some people to stop taking them. But these studies had serious methodological flaws. Moreover, several recent studies, including a meta-analysis in February 2015, have been reassuring about calcium's safety.
Still, to err on the side of caution, don't exceed 1,000 to 1,200 milligrams of supplemental calcium a day. On days when you eat lots of calcium-rich foods (including those fortified with calcium), you can skip the supplement or take less. If you're prone to kidney stones or take thyroid hormones, corticosteroids, or tetracycline, check with your doctor before taking calcium pills.
Vitamin DThough the skin makes vitamin D in response to sunlight, it's estimated that at least half of Americans have blood levels considered either insufficient or deficient (few foods are good sources). Vitamin D works with calcium to keep bones strong and, as we discussed in Vitamin D: What's the Latest?, is being researched as a preventive or treatment for more than 100 disorders—from cancer and heart disease to diabetes and multiple sclerosis. Despite thousands of studies, the jury is still out about these potential benefits, except regarding bone health and muscle function. Major clinical trials are underway.
Meanwhile, unless you've had your blood level of D measured and been told it’s adequate, consider taking a supplement. The RDA is 600 IU a day (from food and supplements) through age 70, and 800 IU for those over 70. We recommend 800 to 1,000 IU of supplemental vitamin D a day for most people, though your health care provider may advise a higher dose if your blood level is very low or if you have osteoporosis, inflammatory bowel disease, or certain other disorders.
Folic acidFolic acid is the form of the B vitamin folate used in supplements and fortified foods. Folate is essential for healthy cell growth and thus is especially important during pregnancy. Inadequate folate intake increases the risk of neural tube birth defects. Since folic acid is better absorbed than the folate naturally found in foods, the U.S. Preventive Services Task Force and the March of Dimes advise a daily multivitamin containing folic acid for women who may become pregnant. The adult RDA is 400 micrograms (the amount in most multivitamins and also the Daily Value used on labels), and 600 micrograms (the amount in prenatal vitamins) during pregnancy. There are also separate folic acid supplements.
Many studies have linked a high folate intake from food or supplements with a reduced risk of colon cancer, but a few studies have suggested that high doses may actually increase the risk. Research is also inconsistent regarding high intakes of folate (usually 1,000 micrograms a day or more) and breast, prostate, and lung cancer.
To be on the safe side, men and postmenopausal women should not take folic acid supplements. They should limit their intake of folic acid from multivitamins and fortified foods to not much more than the RDA—especially if they have had colon cancer or polyps. It's easy to consume more than 1,000 micrograms a day.
Vitamin B12This vitamin is vital to almost every cell and body system, including the blood and the nervous system. In particular, it is crucial in keeping the aging brain healthy. Many people over 50 don't produce enough stomach acid to adequately absorb B12. The vitamin is found naturally only in animal products, so vegans can be deficient unless they eat fortified vegetarian foods or nutritional yeast or take a multivitamin.
The RDA for vitamin B12 is 2.4 micrograms a day. It’s easy to get that much from food if you eat animal products and fortified foods. Because older people absorb less of this vitamin, we recommend they consume at least 6 to 15 micrograms daily from food and supplements. The B12 in supplements and fortified foods is more readily absorbed than that found naturally in foods. Most multivitamins have at least 6 micrograms; "senior" formulas often have 25 micrograms. If you are diagnosed with a B12 deficiency, you’ll need even higher doses.
Multivitamin/mineral pillsThe most commonly used supplements in the U.S., these contain at least 10 vitamins and 10 minerals; they usually provide 100 percent of the Daily Value for most of these nutrients, though many contain higher doses. Multis contain relatively small amounts of calcium, however.
Most randomized clinical trials on multis have yielded disappointing results. Thus, in 2014 the U.S. Preventive Services Task Force concluded that there is still "not enough evidence to assess the balance of benefits and harms" of taking multis (or most other vitamin or mineral supplements) for the prevention of cardiovascular disease or cancer. If multis have an effect, it is likely to be small or may occur in just a small subgroup of people.
Despite the lack of evidence supporting the use of multis for the general population, there are some groups for whom a basic multi (supplying 100 percent of the Daily Value for most vitamins and minerals) makes sense. In some cases, a multi is simply an easy, inexpensive way to get one or two vitamins or minerals they may need.
- Women who may become pregnant should take folic acid to help prevent birth defects, as previously noted, and a basic multi is an easy way to get it. Premenopausal women may also benefit from the iron in a multi.
- Pregnant or breastfeeding women should probably take a multi, but need to discuss this with their health care providers. There are many prenatal formulas.
- Strict vegetarians (vegans), who eat no animal products, may not get enough vitamin B12, zinc, and iron, which a multi can provide.
- People on prolonged, restrictive weight-loss diets (particularly ones that are very low in calories) or other special diets may fall far short in nutrients. The same is true of people who are recovering from surgery or have a serious illness that disrupts normal eating.
What about older people? Though there have been few long-term studies focusing on multis in people over 65, the supplements may help prevent deficiencies in those with reduced appetite and inadequate nutrient intakes. Moreover, older people may benefit because they tend to have reduced absorption and utilization of certain nutrients. In addition, they are more likely to be on medications—notably proton pump inhibitors or H-2 blockers (for heartburn and reflux disease)—that block absorption of some nutrients. Major problem nutrients for this age group include vitamin D, vitamin B12, and magnesium.