More than half of U.S. adults take dietary supplements, such as multivitamins and calcium, and their use jumped dramatically over a recent 20-year period.
Between 1994 and 2006, the proportion of Americans using at least one dietary supplement jumped from 42 percent of adults to 53 percent, according to the U.S. Centers for Disease Control and Prevention.
"The increase in supplement use may be due to increased awareness and education about dietary supplement use," said lead report author Jaime Gahche, an associate service fellow in the CDC's National Health and Nutrition Examination Survey/Planning Branch at the National Center for Health Statistics.
Media attention on vitamin D likely boosted intake of that supplement, she said, and massive advertising by the supplement industry may have influenced use of multivitamins. But some experts say multivitamins may not be necessary.
However, since 2006, the growth in supplement usage has leveled off, she said. "We have reason to believe it should stay relatively stable," she added.
The data for the report were gathered from the National Health and Nutrition Examination Survey (NHANES) and included three time periods: 1988 to 1994, 1999 to 2002 and 2003 to 2006.
Among the report's other findings:
Samantha Heller, a dietitian, nutritionist, exercise physiologist and clinical nutrition coordinator at the Center for Cancer Care at Griffin Hospital in Derby, Conn., said supplement makers promote the idea that dietary supplements will provide people with all the nutrients they need.
While some studies suggest a benefit in taking multivitamins, the most commonly used dietary supplement, others do not, Heller said.
"The general recommendation from health professionals is that we get the bulk of our nutrients, vitamins and minerals from foods, and that if we are eating a healthy diet we may not need most supplements," she said.
Both over- and under-supplementation can be a problem, she noted. "Supplement use is complicated in part because many of the foods we eat are fortified with some vitamins and minerals and not others," she said.
Also, with up to 50 percent of Americans reportedly dieting at any given time, many miss out on essential vitamins and minerals, Heller said. "Combine this trend with the popularity of fast and junk food, which are nutrient-poor and calorie-rich, and it is difficult to make broad dietary supplement recommendations that apply to everyone," she said.
"I generally advise my patients to take a multivitamin, vitamin D, omega-3 fatty acids and for women, calcium, in addition to a healthy diet and lifestyle," Heller said.
"Growing children, athletes, the elderly and people with certain illnesses may need additional or different supplementation," she added.