A recent national survey found that 14% of all people in the U.S. are using some type of herbal medicine. Middle aged women were the largest users of herbal medicines; 23% of the surveyed women in this age group had used an herbal supplement in the last week. Similar results were found in two other surveys. Common reasons women give for using herbal medicines include treatment of: menopausal symptoms, premenstrual syndrome, and menstrual irregularities, as well as to aid breastfeeding, decrease breast cancer risk, prevent recurrence of breast cancer, and change breast size. This fact sheet will focus on uses of herbal medicines that could potentially affect breast cancer risk.
There are several ways that herbal medicines are prepared and taken. The method of preparation is important because different preparations of the same herb can contain different ingredients and have different uses and safety. Herbs can be used fresh, dried or as alcohol or water extracts; for example tea is a water extract of an herb. Most herbal medicines are given by mouth but some are used on the skin, as enemas, or as suppositories. Aromatherapy is also used and involves the inhalation of essential oils (volatile distilled oils from plants) or the use of essential oils to scent massage oils.
Only a few herbs have been studied in randomized, double-blind, clinical trials, the type of study that provides the strongest evidence for the effectiveness of a medical treatment. Without the kind of evidence that comes from a clinical trial it is very difficult, if not impossible, to judge the safety and efficacy of herbal medicines. In the absence of evidence from a clinical trial, the potential effectiveness of an herbal medicine can only be judged based on traditional use or research that can only assess one narrow aspect of an herbal medicine. For example, there are cellular and animal studies that can give an estimate of the biological activity of herbal medicines and their potential for various treatments, but these studies poorly reflect their safety and efficacy in the human body. Nonetheless, a single clinical trial can give misleading results. Consistent results from several well designed and conducted clinical trials are needed to be sure a medicine is safe and effective.
The National Institutes of Health has recently established the National Center for Complementary and Alternative Medicine to provide funding, support and encouragement of rigorous research on complementary medicine, including herbs. Their website is located at: http://nccam.nih.gov/.
Herbal and conventional medicines share common historical and biological roots and have similarities. heir basic actions occur by the same mechanisms and the active ingredients in herbal medicines, like those in conventional medicines, can be considered drugs. There are also differences between herbal and conventional medicines. Most conventional drugs contain a single active chemical. In contrast, the individual herbs and multi-herb preparations used in herbal medicine typically contain many active ingredients. Sometimes the presence of more than one active ingredient makes the herbal medicine more effective. But having more than one active ingredient may also cause problems and make it more difficult to use safely and effectively. This is because multiple active ingredients in herbs may have different strengths or degrees of effectiveness, and they may also work on different biological systems in the body, which can be related or unrelated to the health problem being treated.
Herbal and conventional medicines also typically contain different amounts of active ingredients. In most, but not all, cases the active ingredients in herbal medicines are more dilute than those found in conventional medicines. This presence of lower amounts of active ingredients decreases the potential for problems with their use, but it can also limit effectiveness. Nonetheless, both herbal and conventional medicines should be used with care because all drugs carry the possibility of harmful or ‘adverse’ effects on health.
Herbal and conventional medicines also differ in consistency. The amount and purity of the single active ingredient found in most conventional medicines are monitored and controlled. In contrast, herbal medicines can vary in both active ingredient levels and purity. The various active ingredients in herbal medicines can vary widely since they can be affected by the conditions in which the source plants are grown and how they are processed. Large differences in the amounts of active ingredients have been reported for a number of herbs both from the same producer and among different producers. Standardized extracts, which contain a minimum level of a specific chemical in the herb, are available for some herbs. But there are only a few herbs for which the active ingredients are known.
Although herbal medicines have been used for a much longer time than conventional medicines, the safety and effectiveness of conventional medicines has been studied more and is much better understood. This is mainly the result of government regulations that require that the manufacturers of conventional medicines must present proof of the safety and effectiveness of the medicine, as well as, guidelines for its use to the U.S. Food and Drug Administration (FDA) before the product is marketed. Table 1 lists additional regulatory requirements that the FDA requires for conventional drugs. These regulations add considerably to the cost of releasing a new drug but produce a substantial level of understanding of the medicine. This greatly increases the amount of confidence consumers can have in a drug’s safety and effectiveness.
In contrast, almost all herbal medicines used in the U.S. are classified as dietary supplements and as such, they are regulated like foods. Because of this there are few regulatory requirements for these products (see Table 1). Manufacturers are not required to demonstrate either the effectiveness or the safety of herbal medicines (supplements) before they are sold. Further, if an herbal medicine is unsafe, this condition must be demonstrated by the FDA, instead of the manufacturer needing to demonstrate safety. Proof of a lack of safety is also complicated by the absence of a requirement that manufacturers record and report adverse effects of herbal medicines. Some monitoring of adverse effects is required but by the much less strict system designed to oversee adverse effects of foods. In addition, the manufacturers do not have to test the quality of the final product as they do for conventional drugs. This has unfortunately set up a system where herbal medicines are considered safe until enough adverse events occur to prompt the FDA to prove otherwise. Such an open market for these medicines has been highly criticized and has been described by some as “a disaster waiting to happen.” This absence of regulation offers producers and consumers of herbal medicines a great deal of freedom about what kinds of herbal medicines are available, but it also gives consumers very little confidence that the herbal supplements available to them are either effective or safe. The National Research Council has recently proposed a new revised framework for the evaluation of the safety of dietary supplements including herbs.
In other industrialized countries, there is more strict regulation of herbal medicines than in the U.S. For example, the European Union has recently updated its legislation regulating herbal medicines. Under this legislation all herbal medicines undergo regulation. Traditional herbal medicines are less regulated, in that they do not have to demonstrate effectiveness. But there are regulations regarding the demonstration of safety, the specificity of labeling, the manufacturing procedures and the product quality. In addition, manufacturers must be licensed.
Just because herbal medicines are “natural” products does not mean they are safer than conventional medicines. The ingredients in herbal medicines, that can lead to health problems or adverse effects, are generally found in lower amounts in plants, making it more difficult to get a large dose. But many herbal medicines are concentrated to increase effectiveness and this process may also eliminate this potential ‘margin of safety.’ Detection of adverse effects is also more difficult for herbal medicines as they are currently marketed in the U.S. There is no focused safety testing of herbal medicines or required reporting of adverse effects. Detection by individual doctors is very limited in scope. In most cases, an individual doctor would have to treat an exceedingly large number of patients with the same medicine before an adverse effect could be detected.
Many problems, some of them serious, have been reported when herbal medicines are used. Some of these problems come from the herbal medicines themselves. Others come from interactions of herbal medicines with other medications; many of these interactions have been reported. Some examples are shown in Tables 2 and 3 below.
Several studies have also reported various types of contamination of herbal medicines. Contaminants in herbal medicines that have been reported include other herbs, microorganisms, toxins produced by microorganisms, pesticides and toxic heavy metals. In addition there are many reports of herbal products being adul-terated with conventional drugs. Several of these problems have resulted in deaths.
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