FRIDAY, Jan. 3, 2003 (HealthDayNews) -- A large number of Americans are involved in a kind of health-care underworld, attempting to self-treat or prevent diseases with various vitamin and mineral supplements, a new study says.
More than half of Americans use vitamin or mineral supplements (or both) and, researchers say, much of this supplement use was associated with various medical conditions.
The study appears in the January issue of the American Journal of Preventive Medicine.
"We have evidence that people are taking up to 16 supplements a day [although] on average people were taking two to three supplements," says Jessie Satia-Abouta, lead author of the study and an assistant professor of nutrition at the University of North Carolina at Chapel Hill. (The research was done while Satia-Abouta was at Fred Hutchinson Cancer Research Center in Seattle.)
"It's really important for health-care providers to know what supplements their patients are taking," Satia-Abouta says. "I've never been asked by my doctor if I'm taking dietary supplements."
Dr. Jay Brooks, chief of hematology/oncology at the Ochsner Clinic Foundation in Baton Rouge, La., estimates that 70 percent of his patients are taking some kind of supplement.
"There's this general feeling that the medical establishment is holding something back," he says. "There's almost this conspiracy theory."
Satia-Abouta and her colleagues analyzed information from the Vitamins and Lifestyle (VITAL) Study, in which 45,748 men and women aged 50 to 75 completed a 24-page questionnaire regarding supplement use (multivitamins plus 15 individual vitamins or minerals), diet, physical activity, medical history, and demographic characteristics.
"This is a cohort study, which means that you gather information from a bunch of people then try over time to see if they develop a disease," Satia-Abouta explains. The study was originally conceived to look at the link between cancer and supplement use, but that information is not yet available.
In this round of analysis, the researchers found that 75 percent of the participants regularly took a vitamin or mineral supplement. More than half were taking a multivitamin. The most popular single supplements were vitamins E and C, calcium, folate, and selenium. The participants who were most likely to be using supplements tended to be older, female, highly educated, Caucasian, and with a normal body mass index.
"Education correlates with income, and supplements are not necessarily cheap," Satia-Abouta says. "These people probably have more money and they know more about trends."
Respondents who had medical conditions reported using more supplements than respondents who did not have medical conditions. The strongest associations were for people with or at risk for cardiovascular disease taking vitamin E, niacin, and folate, and for people with indigestion and acid reflux disease taking calcium.
Although women used more supplements overall, in certain cases men were more likely than women to use supplements. For instance, men who had been diagnosed with an enlarged prostate were more likely to take selenium. (In fact, according to preliminary studies, selenium may reduce the risk of prostate cancer but not an enlarged prostate.) Men with depression and coronary disease also used more supplements than women.
Much of the supplement use could reflect trends in the media. "Today, vitamin E is good. Tomorrow, vitamin C is good. People will buy all the ones they hear about, which is one a day in the media," Satia-Abouta speculates.
The researchers did not look at adverse health effects or why people take certain vitamins and/or minerals. The ill effects of supplement use are a real risk.
"There's this tremendous deregulation of the herb and vitamin industry, where nobody has to report what's in a product or if it's any good," Brooks says. Excessive amounts of vitamin C may make radiation less effective.
The current study did not look at herbal supplements, but there's evidence that St. John's wort affects the toxicity of certain chemotherapies; Brooks has seen liver failure in four patients who drank an herbal tea made from a bush in the Mojave Desert.
"People feel that taking something 'natural' is really the way to go," Brooks says. "Well, we use natural products in medicine every day. The problem is that people don't understand the science behind it."
What To Do
For more on vitamins and minerals, visit the Food and Nutrition Information Center at the U.S. Department of Agriculture or North Dakota State University.
