Vitamins, minerals, amino acids, some steroids, the pineal hormone melatonin, and herbal supplements all fall under the heading of nutritional supplement. The Food and Drug Administration classifies dietary supplements as foods, and not as drugs, so they are regulated differently than prescription drugs.

The FDA requires the manufacturer ensure the safety of their product before it goes to market. The Food and Drug Administration will only take action against any unsafe nutritional products after it reaches the marketplace.

Nutritional supplements are any product that is intended to supplement the diet and contain any of the following dietary ingredients:

A vitamin
A mineral
An herb or other botanical (excluding tobacco)
An amino acid
A dietary substance for use by people to supplement the diet by increasing the total dietary intake, or
A concentrate, metabolite, constituent, extract, or combination of any of the above

Furthermore, it must also conform to the following criteria:

It is intended for ingestion in pill, capsule, tablet, powder or liquid form.
It is not to be represented for use as a conventional food or as the sole item of a meal or diet.
It is labeled as a dietary supplement.
While hormones are not included in the above list, some hormones are labeled as "dietary supplements".

Dietary supplements are permitted to make structure and/or functional nutritional value claims. These are broad claims that the product can support the structure or function of the body, as in "glucosamine helps support healthy joints", "the hormone melatonin helps establish normal sleep patterns". The FDA must be notified of these claims within 30 days of their first use, and there is a requirement that these claims be substantiated.

Keep in mind the possibility of interactions between a prescription drug and nutritional supplement. Just because a product is derived from "natural" or "herbal" sources does not assure its safety.

Many herbal products produce pharmacological side effects. Just because herbal products are available without a prescription, medical advice is necessary because of the adverse effects of these products and the potential for drug interactions.

The bottom line is, in order to protect yourself; it is highly recommended you investigate a nutritional supplement before you start taking it. Make sure plenty of studies have been conducted that show its nutritional value, safety and effectiveness. A good rule of thumb is to evaluate whether you are already getting enough of the vitamin, mineral or herbal supplement through your dietary intake, without additional supplementation.

Eating a healthy, nutritious diet is preferable, if that is a feasible option. If you recognize you are falling short of recommended daily allowances, ask your physician or nutritionist what supplements and dosages he recommends.