Benefits and risks of hair, skin, and nail supplements in older adults.

Many older adults, particularly older women, use over-the-counter supplements for antiaging benefits, including for hair and skin. The supplement industry is unregulated by the Food and Drug Administration, and the interactions between supplements and medications are often overlooked by both patients and physicians. This article discusses the proposed mechanism of action, common misconceptions, possible benefits, and potential side effects of the most commonly used antiaging skin supplements by women, including biotin, nicotinamide, hyaluronic acid, collagen, zinc, vitamin C, vitamin A, vitamin E, and other antioxidants. Supplements may also interfere with common blood tests, such as biotin with the thyroid and troponin cardiac enzyme tests, which patients and their clinicians must be aware of and account for when interpreting lab results. Other supplements, such as zinc, are commonly taken in excess and may result in deficiencies in the absorption of other minerals, such as copper. Over-supplementation of fat-soluble vitamins, such as vitamin A and vitamin E, can result in toxic levels since excess is not excreted in the urine. The clinician caring for older patients' skin and nails must ask older patients about supplement use and be aware of the potential harms of these supplements in some patients.