A recent survey estimated that more than 38 million adults in the United States used herbal products and dietary supplements in 2002.
[1] More than half of those users said that these products were important to their health and well-being, yet only one third told a conventional healthcare provider about their use.
Other reports have estimated that 25% of patients who seek medical attention for a serious medical problem are using “unconventional” therapies, and 70% of those patients do not disclose those practices to their physician.[2,3] One survey estimated that about 18% of the US population uses herbal therapy on a regular basis.[4]
Herbal products and dietary supplements are widely available in supermarkets and other retail outlets, as well as by mail order. In fact, only a small percentage of these products (4.5%) are actually sold in pharmacies.[5] Many patients believe they derive health benefits from these herbal preparations, yet some remain skeptical and may seek advice from health professionals prior to use. Thus, it is important for all health professionals to be informed about available products and to be aware of any potential problems associated with their use.
Concerns About Herbal Products and Dietary Supplements
Unlike prescription and over-the-counter drugs, herbal products are not regulated by the US Food and Drug Administration (FDA) to determine purity or potency.[6] In fact, some products may contain contaminants, and their potency is dependent on many factors, such as the climate and soil conditions where they are grown, harvested, and stored.[7] Some herbal preparations have even been found to contain prescription drugs and heavy metals as unlabeled ingredients, and in some cases, these contaminants have resulted in toxicities.[8-17]
The labeling of herbal products is regulated by the Dietary Supplement Health and Education Act of 1994 (DSHEA).[18] Under this law, manufacturers may only make general claims about a supplement’s effect on the structure or function of the human body (eg, “supports the immune system”). They must include the following statement in their labeling: “This product is not intended to diagnose, treat, cure, or prevent any disease.”
The labels on herbal products are designed to promote product use and not necessarily to inform the consumer, so health professionals should be equipped with a general understanding of popular herbs and supplements, including knowledge of efficacy, common side effects, risks, and interactions. In addition, they should prospectively seek information regarding their patients’ use of unconventional medicines to avoid adverse consequences.
Consumers should be advised that manufacturers of herbal supplements are not required to demonstrate safety or efficacy prior to marketing. Before the FDA can remove a product from the market, the agency must prove that the product is unsafe or ineffective. Recent examples of this include the ban on products containing ephedra due to adverse cardiovascular effects,[19] and the prohibition of kava amid concerns about hepatotoxicity.[20]
Patients with medical illness should not use herbs and dietary supplements without medical supervision. As will be discussed, some herbal products have adverse effects and may interact with prescribed medications. Furthermore, many conditions that patients try to diagnose or treat themselves may be serious, requiring a careful history and examination by a healthcare professional. For example, unsupervised use of saw palmetto for urinary symptoms may delay a diagnosis of prostate cancer.[21] Similarly, patients with symptoms such as chronic insomnia, anxiety, and depressed mood should see their health provider. Patients with cardiovascular disease, hypertension, heart failure, and hyperlipidemia should be under a healthcare professional’s care and receive appropriate prescription drugs.
The following is an overview of some of the most commonly used herbal products, including important clinical considerations in the use of these products.
Echinacea for Fighting Cold Symptoms, Boosting Immunity
Echinacea is one of the most popular herbs in the United States, extracted from the purple coneflower that is native to North America. Species include Echinacea purpurea, Echinacea angustifolia, and Echinacea pallida. It has been studied as an adjunct therapy to enhance the immune system, mostly in upper respiratory tract infections, and these studies have produced mixed results.[22,23]
A recent meta-analysis concluded that standardized extracts of echinacea were effective in the prevention of common cold symptoms after clinical inoculation, when compared with placebo.[23] The authors of that study concluded that the likelihood of experiencing a cold was 55% higher with placebo than with echinacea (P < .043).
Some antiviral and bacteriostatic properties have been demonstrated in vitro, and the herb also appears to stimulate the production of cytokines (interferon, tumor necrosis factor, and interleukins).[24] Animal studies have revealed probable mechanisms of echinacea-induced immune enhancement, such as increasing the number of circulating white blood cells.[25]
Common side effects of echinacea supplements include unpleasant taste and allergic reactions. Because the flower is related to ragweed, cross allergenicity may occur in individuals allergic to ragweed.[26,27]
Echinacea is not recommended in patients with progressive or autoimmune disorders, including acquired immunodeficiency syndrome, tuberculosis, multiple sclerosis, collagen disorders, and diabetes mellitus. Theoretically, since echinacea alters the immune system, these disorders may be exacerbated.[28,29] Persistent use of echinacea has been associated with hepatotoxicity, so it should not be taken by patients who are taking other known hepatotoxins such as anabolic steroids, amiodarone, methotrexate, or ketoconazole.[30]
While not all randomized controlled trials performed to date have shown benefit for Echinacea over placebo,[22,31] a Cochrane review in 2006 concluded that the aerial parts of Echinacea purpurea might be effective for early treatment of colds in adults.[32]
Unfortunately, the optimal dose of echinacea is unknown, and multiple formulations exist, such as capsules, tinctures, teas, and extracted plant juice. Recommended dosages vary widely; for instance, capsules of Echinacea purpurea extract range from 100 to 500 mg, with manufacturers’ suggested use ranging from 1 to 4 times daily for common cold prevention.
Take-home message: Clinicians should inform patients that a wide variety of Echinacea preparations and doses have been studied and results are inconsistent, making it difficult to recommend specific products. However, E. purpurea seems to be modestly effective for preventing the common cold in those at risk (eg, sick contacts). Evidence that the herb may reduce the duration of cold symptoms has been mixed. Patients allergic to ragweed, with progressive autoimmune disorders, and on hepatotoxic drugs should avoid echinacea. Leer más…
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