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:
- More women (59 percent) than men (49 percent) use supplements.
- Use of multivitamins, the most commonly consumed supplement, rose from 30 percent in the earlier period to 39 percent by 2003-2006.
- Calcium use by women 60 and older increased from 28 percent to 61 percent across the three time periods, but varied by race and ethnicity. More than two-thirds of white women 60 and older (65.7 percent) were taking calcium-containing supplements in 2003-2006, up from 58.9 percent in 1999-2002. Among Mexican American women, 52.3 percent were using calcium supplements in 2003-2006, an increase from 39.5 percent. Increased use of calcium among black women was not statistically significant, the researchers noted.
- Consumption of folic acid supplements, recommended for women of childbearing age, also varied by race and ethnicity, but stayed at about 34 percent from 1988 to 2006, Gahche's group found. White women aged 20 to 39 are twice as likely to take a supplement containing folic acid as blacks or Mexican Americans. Folic acid helps prevent neural tube defects in babies. Folate is found in green leafy vegetables and beans.
- Twenty-four percent of men and 30 percent of women took vitamin D in 1988-1994, a figure that stayed stable for younger adults but increased for men and women ages 40 to 59. Use of vitamin D, which is difficult to obtain in foods, also increased among women 60 and older, jumping from 49.7 percent to 56.3 percent from 1999-2002 to 2003-2006.
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.