Q. Are vitamin supplements (like vitamin D) good for your health, and can you tell me who might benefit from taking the pills?
A. Most of us living in developed nations and eating a balanced diet don’t need a daily multivitamin or specific vitamin pills—but there are situations where we do.
Women of childbearing age should take a folic acid pill every day (in the range of 0.4 to 0.5 micrograms). Folic acid supplements protect against babies being born with neural tube defects. The value of folic acid supplements in pre-venting cancer and heart disease, which had been suggested by studies 20 years ago, has not been confirmed by randomized trials.
People who are at increased risk for developing osteoporosis (most older adults) are likely to benefit from a regular vitamin D supplement. Authorities differ as to the dose. In my opinion, a dose of 1,000 international units (IU) per day is generally beneficial and safe.
In developing nations, vitamin A supplements reduce death rates in children. However, they are unnecessary in developed nations like the United States.
Some people need vitamin supplements because they have particular medical conditions that can lead to deficiencies. People who do not have a regular balanced diet—because they are poor, abuse alcohol, or have dietary restrictions (like being vegans), for example—may well need particular vitamin pills. The same is true for people with various gut conditions—like Crohn’s disease, celiac disease, chronic diarrhea, or gastric bypass surgery—that interfere with the absorption of vitamins in food. People on dialysis for kidney failure need vitamin supplements. Adults of all ages who get very little exposure to sunlight—for example, those who are homebound or in an institution—may need vitamin D supplements.
There are some people who are born with a genetic condition that interferes with the metabolism of B vitamins. I’m one of them. People like us need to take a high-dose vitamin B supplement each day.
Even if taking regular vitamin pills has not proved to be beneficial for most of us, is it harmful? Taking one multivitamin a day almost surely is not harmful, unless the pill contains a dose of vitamin A that is higher than 2,500 IU or a dose of vitamin E that is higher than 30 IU. High daily intake of vitamin A (more than 10,000 IU) can increase the risk of birth defects and osteoporosis. Beta carotene pills increase the risk of lung cancer in people who are already at increased risk (like smokers). Daily vitamin C pills may increase the risk of kidney stones.
Finally, the evidence about vitamin pills is not all in. For example, several theoretical health benefits from regular vitamin D pills are being tested in large studies. We will keep you updated about important new research.
—Anthony L. Komaroff, M.D.
Editor in Chief
Harvard Health Letter