Watching What You Mix with Your Rx

Dietary supplements taken with prescription medications among many US adults

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) It may seem harmless to pop a multivitamin each day, but many dietary supplements still contain active ingredients that affect the body. They might also interact with prescription medications.

A recent study found that about one in every three adults took both dietary supplements and prescription medications simultaneously.

The most common supplements taken among US adults were multivitamins and antacids, the study found.

Those with a diagnosed medical condition were more likely to take supplements along with prescription medication, compared to those without a medical condition.

Taking supplements like multivitamins, especially those with added herbs or fish oil, may interfere with prescription medications. Therefore, doctors need to be aware of all the supplements that their patients may be taking if the patient is taking prescription medications.

"Tell your doctor about the supplements you take."

This study, led by Emily Farina, PhD, RD, a fellow at the Oak Ridge Institute for Science and Education in Belcamp, MD, aimed to learn more about adults' use of dietary supplements and prescription medication.

The researchers analyzed data from 9,950 adults, aged 20 and older, who were involved in the 2005-2008 National Health and Nutrition Examination Survey in the US.

The researchers found that about one third of US adults (34 percent) reported regularly taking both dietary supplements and prescription medications.

Those who had a medical condition, the study showed, were about 2.6 times more likely to take dietary supplements and prescription medications than those with medical conditions diagnosed by a doctor.

Overall, 47 percent of those with a doctor-diagnosed medical condition took supplements and prescription medications, compared with just 17 percent of those without a diagnosed medical condition.

This finding remained true even after the researchers had taken into account differences between the participants' age, sex, educational level and household income.

However, women were found to be more likely than men overall to take dietary supplements.

Participants aged 60 and older were also more likely to take supplements and prescription medications than younger adults.

The most common condition found among those taking both dietary supplements and prescription medications was osteoporosis.

Also common among those taking supplements and prescription medications were cancer, arthritis, diabetes and heart, kidney, respiratory or liver conditions.

Among those with diagnosed medical conditions, the most commonly prescribed medications were cardiovascular ones.

The most commonly prescribed medications among those without a medical condition were hormones, including birth control pills.

The researchers also found that US adults with medical conditions were more likely to take multivitamins with added ingredients, such as fish oil, herbs or botanicals, than they were to take plain multivitamins.

These findings reveal that having a medical condition may increase the likelihood that someone taking prescription medications will also take dietary supplements.

"The increasing complexity of combinations of ingredients contained in dietary supplements may require explicit evaluation by health care and dietetics practitioners," the researchers wrote.

This study was published April 7 in the Journal of the Academy of Nutrition and Dietetics. The authors reported no conflicts of interest.

The research was funded by the US Army Medical Research and Material Command, the Department of Defense Alliance for Dietary Supplement Research and the Oak Ridge Institute for Science and Education with the Department of Energy.

Review Date: 
April 30, 2014
Last Updated:
May 1, 2014