Unlike many prescription medications, nutritional supplements are easily available to anyone and do not require a doctor’s signature. While these are generally seen as “harmless,” many people do not realize supplements can contain the same ingredients as prescription drugs and pose their own dangers of side effects and/or interactions. According to a study appearing in the New England Journal of Medicine, nutritional supplements were responsible for 23,000 emergency room visits and more than 2,000 hospitalizations yearly between 2004 and 2013.

A recent survey by the American Osteopathic Association found that approximately 86 percent of Americans regularly take vitamins or supplements, generally for nutritional deficiencies. However, fewer than one-quarter of these people have a medical need and would do better to get their nutrients through the food they eat.

For example, Vitamin D, which one can obtain from dairy foods and sunlight, is important for bone health. However, too much can cause anorexia, excessive urination, and irregular heartbeat. A person who takes too much Vitamin D also risks tissue calcification (hardening of tissues due to excess calcium deposits) as well as heart and kidney injuries. Likewise, Vitamin A is necessary for healthy immune and organ function and is present in many fruits and vegetables. In excess, however, it can cause headaches and nausea; in extreme cases, coma and even death can result.

Potassium has been demonstrated to help lower blood pressure, and some people take supplementary potassium for this reason. High doses can cause irregular heartbeat and even cardiac arrest, which is why the FDA has limited OTC potassium tablets to under 100 milligrams. Potassium can also interact with prescription blood pressure medications, such as ACE inhibitors and diuretics. A better choice: eat more bananas and avocado, which are rich sources of potassium.

The same goes for iron. Iron supplements are sometimes prescribed for anemia along with medications that stimulate the production of red blood cells, but in many cases, iron deficiency is due to an underlying condition. Too much iron, particularly for those with no medical need, can cause digestive problems, constipation, and impaired zinc absorption, and even result in organ failure. Foods rich in iron include legumes and spinach as well as meat, fish, and poultry.

Some supplements are used as substitutes for psychoactive drugs used to treat issues such as anxiety and depression. Case in point – St. John’s Wort, often taken for depression, ADHD, and obsessive-compulsive disorder. It also interacts with several pharmaceutical drugs that include warfarin, contraceptives, and anti-rejection drugs taken by transplant patients. When taken with selective serotonin reuptake inhibitors (the most commonly-prescribed antidepressants), St. John’s Wort can cause serotonin syndrome, the symptoms of which are agitation, overactive reflex response, fever, excess sweating, tremors, and diarrhea.

Kava kava, used by people with anxiety disorders, is a member of the pepper family and used by Pacific Island peoples for relaxation. While research confirms this effect to a degree, it can also result in liver damage, heart problems, and skin and eye irritation.

The takeaway here: be cautious when taking nutritional supplements, particularly if you are on prescription drugs – and consider food sources as an alternative.

K.J. McElrath is a former history and social studies teacher who has long maintained a keen interest in legal and social issues. In addition to writing for The Ring of Fire, he is the author of two published novels: Tamanous Cooley, a darkly comic environmental twist on Dante's Inferno, and The Missionary's Wife, a story of the conflict between human nature and fundamentalist religious dogma. When not engaged in journalistic or literary pursuits, K.J. works as an entertainer and film composer.