Common adverse interactions for vitamins and supplements
According to a recent Gallup Poll, a record number of Americans are taking some type of daily vitamin or supplement.1 A December 2013 survey found that 50 percent of Americans said they took a multivitamin or other nutritional supplement at least once a day. More than half of those who took some type of vitamin or supplement were female (56 percent). Furthermore, vitamin and supplement use will increase with age, education, and income level:1
- 68 percent of Americans over the age of 65, compared to 36 percent of those between the ages of 18 and 29
- 65 percent of Americans with a postgraduate degree, compared to only 43 percent of those with just a high school degree
- 56 percent of Americans making upward of $90,000 per year
On top of all these vitamins and supplements, Americans are also likely to have one or more prescription drugs in their medicine cabinets. A study from the Mayo Clinic found that as many as 70 percent of Americans take at least one prescription drug, and more than half of all Americans take two such medications.2
These facts tell us there is a good chance that patients are taking prescription medications and vitamins or supplements at the same time. Unfortunately, some prescription medications may not interact well with vitamins or supplements. Although there can be hundreds of possible adverse combinations between medications and vitamins or supplements, there are several common ones, according to U.S. Pharmacist.3
Common vitamin and supplement interactions
- Vitamin A: Vitamin A is usually found as part of a multivitamin, rather than on its own. It is thought to help boost vision, bone growth, and the immune system. If a patient is prescribed any of the retinoid drugs (most commonly found as the acne medication Accutane), it can actually lead to toxic levels of Vitamin A, resulting in dizziness, nausea, vomiting, or blurry vision.3
- Calcium: Calcium is usually taken to help strengthen the bones. Unfortunately, certain antibiotics, such as tetracycline, may have their bioavailability reduced by as much as 40 percent if taken when calcium is present in the body. Patients who normally take calcium should consider upping their dosage if they are prescribed antibiotics.3
- Vitamin E: Vitamin E is often recommended for any number of conditions, ranging from arthrosclerosis, to Alzheimer’s disease, to cancer. However, there may be a risk of excessive bleeding if Vitamin E is taken with any of the blood thinners, most specifically warfarin. This condition may be more pronounced with higher doses of Vitamin E, so patients may benefit from switching to a multivitamin with Vitamin E, which will contain lower doses.3
- Niacin: The adverse interaction between niacin and any of the statin (lipid-lowering) medications is perhaps the most common, due to the popularity of statins to treat high cholesterol. Patients who are taking statins and niacin may experience myopathy (muscle weakness due to problems with the muscle fibers). They may have muscle stiffness, cramps, or spasms. This interaction is more frequent with doses of niacin at 1 g per day or greater, which is higher than most over-the-counter niacin preparations. Again, advising patients to switch to a multivitamin may be beneficial.3
Patients take vitamins and supplements in order to keep themselves healthy. Despite all good intentions, they may accidentally have an adverse reaction due to bad interactions between vitamins and supplements and prescription medications. A careful DC will ask about any prescription medications patients are taking, not just at their initial visit, but at every visit.
1 Swift A. “Half of Americans take vitamins regularly.” Gallup. http://www.gallup.com/poll/166541/half-americans-vitamins-regularly.aspx. Published December 2013. Accessed May 2015.
2 Mayo Clinic, Olmsted Medical Center. “Nearly 7 in 10 Americans take prescription drugs.” MayoClinic.org. http://newsnetwork.mayoclinic.org/discussion/nearly-7-in-10-americans-take-prescription-drugs-mayo-clinic-olmsted-medical-center-find/. Published June 2013. Accessed May 2015.
3 Ezzo D, Sulli M. Drug interactions with vitamins and minerals. US Pharm. 2007;1:42–55.