It is becoming more common for over-the-counter pharmaceutical products to contain vitamins and minerals. Ads indicate these nutrients support body functions that help to prevent numerous symptoms or treat a medical condition. However, the doses of nutrients in these supplements can be high enough to be functioning more like a drug.

Sadly, people often expect high-dose vitamins and minerals to have rapid beneficial effects like drugs. However, if a symptom such as fatigue is caused by an iron deficiency, it can take weeks to months of proper supplementation to reverse the symptoms. Reversing symptoms related to nutrient deficiencies is never a quick fix.

Question: What are the differences between a drug, an essential nutrient and a nutrient used as a drug?

Answer: A drug is a nonfood substance that when consumed or injected causes a change in body chemistry and physiology, even affecting mental functions. The difference between a drug and nutrient is function and dosage. Drugs are used to treat medical conditions, and more recently drugs are being used to decrease the risk of medical conditions. Prescription drugs come with dosages, uses and warnings regarding side effects. If the dose is correct, symptoms are resolved, and there are no additional unwarranted mild to severe side effects.

Essential nutrients promote growth, tissue repair and a healthy metabolism. The Food and Nutrition Board recommendations for vitamins and minerals were set to prevent nutrient deficiencies and associated symptoms and to support thousands of chemical reactions needed for normal health and metabolism. These nutrient recommendations also include a not-to-exceed upper level to prevent harmful side effects.

Certain nutrients consumed at levels significantly higher than the upper recommended limits have been used in disease treatment. Examples include vitamin A for acne and niacin for tinnitus. But like a number of drugs, excess consumption can cause liver toxicity and should be used only under a physician’s care.

Q: What over-the-counter nutrient products are used as drugs?

A: During the cold and flu season, products containing vitamin C and zinc are commonly used to prevent getting a cold, decrease the number of days with the cold and blunt the intensity of those miserable cold symptoms. Generally, following label recommendations for a few days keep these nutrients at safe levels. However, with the many good-tasting lozenge products, some consumers are using them too frequently throughout winter to prevent colds. Excessive amounts of vitamin C or zinc can each cause nausea, diarrhea and abdominal cramping; excessive zinc is also associated with headaches. Vitamin C also can bias some blood test results.

When a nutrient is one of the ingredients incorporated into a drug, always follow use/dosage directions to prevent harm. Consult your pharmacist for reliable information about any particular nutrient drug issue.

Alan Titchenal, Ph.D., C.N.S., and Joannie Dobbs, Ph.D., C.N.S., are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. Dobbs also works with University Health Services.