Overview of Medicinal Herbs and Nutraceuticals
Medicinal herbs are plant parts, sometimes ground, extracted, or otherwise prepared, used for health benefits. Nutraceuticals, a more recent and more general term, are a group of natural substances that includes certain herbs and such products as cholesterol-lowering margarines and psyllium-fortified products that are used as dietary supplements and regulated as foods.
Traditional systems of medicine have been used throughout the world for centuries. Certain ancient systems, such as traditional Chinese medicine, Ayurveda (the holistic system of medicine from India), and Tibetan medicine, are still used extensively, particularly in their country of origin. In the United States, interest in the therapies of such systems, particularly for the treatment of chronic illness, is growing. These therapies, usually referred to as complementary or alternative medicine (see Overview of Complementary and Alternative Medicine), range from medicinal herbs to acupuncture to massage. Most of them have not been studied scientifically, and nearly all are unregulated.
The most commonly used alternative therapy is dietary supplements, which include medicinal herbs and nutraceuticals. Because the use of dietary supplements is widespread, the United States government passed the Dietary Supplement Health and Education Act (DSHEA) in 1994. It defines a dietary supplement as any product (besides tobacco) that contains a vitamin, mineral, herb, or amino acid and that is intended as a supplement to the normal diet. The act requires that the label of a dietary supplement identify it as such. The label must state that the claims for the dietary supplement have not been evaluated by the Food and Drug Administration (FDA). The label must also list each ingredient by name, quantity, and total weight and must identify the plant parts from which each ingredient is derived.
Most dietary supplements used in alternative medicine are derived from plants, and some are derived from animals. Because such dietary supplements are natural, some people assume that they are safe to use. However, a substance is not necessarily safe just because it is natural. For example, many potent poisons, such as hemlock, are derived from plants, and some, such as snake venoms, are derived from animals. Furthermore, almost all substances that affect the body, whether dietary supplements or drugs approved for medical use by the FDA (see Prescription drugs or nonprescription drugs), can have unwanted side effects.
Because dietary supplements are not regulated as drugs by the FDA, their manufacturers are not required to prove that supplements are safe and effective (although they must have a history of safety). Consequently, few supplements have been studied rigorously for safety and effectiveness (although some may eventually be shown to be safe and effective). Furthermore, because the need to evaluate supplements in humans has been recognized only recently, much of the available information has not been gathered systematically or scientifically and so is difficult to evaluate. In contrast, both prescription and nonprescription (over-the-counter) drugs have been extensively and systematically studied by researchers and reviewed for safety and effectiveness by the FDA (see Drug Effectiveness and Safety). These studies include those in animals to detect the development of cancer and organ damage and those in humans to detect any signs of toxicity.
The amount and quality of evidence supporting the effectiveness of supplements varies greatly. For some supplements, evidence supporting their effectiveness is convincing. However, for most, scientific studies have not been designed well enough to provide clear, reliable answers. For some supplements, the only evidence suggesting effectiveness is reports about individual people or studies conducted in animals.
Other areas of concern are the purity and standardization of supplements. Supplements, unlike drugs, are not regulated to ensure that they are pure or that they contain the ingredients or the amount of active ingredient they claim to contain. As a result, the supplement may contain other substances, including, in some cases, prescription or nonprescription drugs and even dangerous substances such as mercury.
The amount of active ingredient in a dose of a supplement may vary, especially when whole herbs are ground or made into extracts to produce a tablet, capsule, or solution. The buyer is at risk of getting less, more, or, in some cases, none of the active ingredient in a supplement. Standardization requires that each individual dosage form of the product contains a precise amount of its active ingredient or ingredients. However, most herbal products are mixtures of several substances, and which ingredient is the most active is not always known. Therefore, determining which ingredient or ingredients should be considered active and thus subject to standardization can be difficult. Some supplements, particularly those produced in Europe, have been standardized and may include a designation of standardization on the label.
Advice on how to choose a pure, standardized product varies from expert to expert. Most experts recommend buying from a well-known manufacturer, and many recommend buying products made in Germany because oversight of supplements is stricter there than in the United States.
Although the content of a supplement is not standardized, the way in which it is manufactured has been standardized. In 2007, the FDA created current good manufacturing practices (GMPs) that standardize the manufacturing, packaging, labeling, and storing of dietary supplements. These GMPs help ensure the quality of dietary supplements and help protect the public health.
Supplements can interact with prescription and nonprescription drugs. Such interactions may intensify or reduce the effectiveness of a drug or cause a serious side effect. Before taking supplements, people should consult their doctor, so that such interactions can be avoided. Few well-designed studies have been conducted to investigate supplement-drug interactions, so most information about these interactions comes from sporadic individual reports of interactions.