Alternatives to this study for enhancing immune system functioning include prescription medications, exercise, dietary modification, and other nutritional supplements. The risks of medications can be very significant, including life-threatening, but the risk of taking nutritional supplements is not totally understood, since they are not regulated by the US Food and Drug Administration. Medications and nutritional supplements, as part of a change in lifestyle behaviors, may also prove to be beneficial for immune system functioning, but their long-term use has unknown consequences.