By Stephen Z. Fadem, MD, Paul Garney, MS, RD and Bruce T. Smith, MS, RD
The use of herbs as medicine has grown in popularity in this country over the past decade, contributing to a $4.1 billion supplement industry. The popularity of herbs is due to several factors: they can be purchased without a prescription, a belief that "natural" products are safer and the knowledge that many of our modern drugs are derived from herbs. However, there has not been an equal increase in clinical studies. This means that much of the information available to the public is general in nature and not designed for those with specific medical problems. Any supplement use needs to be evaluated in the context of the individual user: their primary diagnosis, any additional conditions and the medications they are taking. It is important to understand that pharmaceuticals and herbs are not regulated to the same degree. In 1994, the Dietary Supplements Health and Education Act was passed by Congress. Under this act, herbs and a number of other biologically active substances are classified as dietary supplements. Regulation of these supplements is based upon adverse events, i.e., they are considered safe until proven harmful (ephedrine as an example). In contrast, drugs must prove they are safe, e.g. clinical trials, before they are allowed on the market. As a result, herbals can contain pesticides, heavy metals, poisonous plants and even conventional medications without impunity. Remember these products are big business and are not coming from your grandmother's garden.
In addition, even pure products may not be supplying ingredients as advertised. ConsumerLab.com (CL), an independent product testing company, has reviewed a number of health products and the results reflect the lack of standardization in the industry. For instance, in a test of 22 brands of ginseng products, only nine passed CL's criteria: eight contained unacceptable levels of pesticide, two contained unacceptable levels of lead and seven contained less than the required levels of active ingredients. All of the companies listed their products as being "standardized."
Further complicating this issue, active ingredients in herbals have often not been identified or may only be effective in the presence of other active ingredients found in the herb. Variables influencing effectiveness include where a plant was grown, which parts were used, and even which variation is used (e.g., Korean vs. American vs. Siberian ginseng).
Another aspect of supplementation used to consider is drug interaction. People with kidney disease are on a number of medications. Herbals can boost or decrease the effectiveness of prescribed pharmaceuticals. Ephedra, often used in weight loss products, causes an increase in heart rate and blood pressure and should not be used in patients with hypertension, congestive heart failure and diabetes. Other examples of negative interactions are: St. John'swort and digoxin, protease inhibitors or cyclosporine; ginseng and anticoagulants or immunosuppressants. It is critical to mention to your physician any herbals, over-the-counter medications and products purchased from health food stores you may be using.
Other herbs that may be problematic are those with diuretic properties. Goldenrod, parsley, uva ursi and juniper berries fall into this category. In fact, juniper and parsley effects are created by irritation of the kidney's epithelial tissue. Other herbals may affect electrolyte balance. Alfalfa and dandelion contain high levels of potassium, of particular concern for those taking potassium-sparing diuretics.
Some herbs have been found to be extremely dangerous. Between 1990 and 1992 the herb Aristolochia, innocently used as a weight loss product, was found to be highly carcinogenic and a direct cause of irreversible kidney failure.
Should someone with chronic kidney disease avoid all herbal products? No, not necessarily. Green tea is an example of an herb that confers benefit with low risk. Research has demonstrated that green tea mildly guards against cardiovascular disease by lowering total cholesterol levels and improving the cholesterol profile (the ratio of LDL cholesterol to HDL cholesterol), reducing platelet aggregation and lowering blood pressure. However, even here caution is advised. Green tea compounds have been reported to enhance vitamin K activity and, thus, can interfere with warfarin dosing. Furthermore, most of the benefits related to green tea have been from observations, animal or in vitro studies and not rigid clinical trials. Controlled research protocols need to be developed to further study this potentially valuable product. Evidence-based medicine builds upon a foundation of studies that meet scientific criteria. There is no reason why selected herbals felt to have potential benefit, such as green tea, cannot undergo large, multicenter research trials.
When facing the uncertainty of a chronic illness, there is temptation to succumb to a product's promises of alleviation or cure. This is especially true with cancer, but also applies to kidney disease. The Web site www.quackwatch.com has informative and valuable articles about dubious medical practices, including herbal supplements. Many herbal products have never been through multicenter, double blind, controlled and randomized trials. Valid data is lacking as to their safety and effectiveness. Anecdotal testimonials are used as substitutes for the valid and rigidly controlled evidence that we have grown accustomed to in the medical practice. Marketing claims that an herbal product has value and is effective can be misleading. The old adage, "If it sounds too good to be true, it probably is," should be kept in mind. Basic healthy living practices will provide the most benefit: for high blood pressure eliminate salt from the diet; for diabetes, be vigilant in monitoring your blood sugars, exercise and eat a balanced diet of fresh foods. These activities also represent areas where you, as the patient, can exercise control over your illness.
In summary, there may be great value to herbal products when used under the proper conditions. However, without controlled clinical trials, data as to their safety and effectiveness is going to be lacking. The public, especially people with any form of kidney disease, should exercise caution when using products of this nature.
Dr. Fadem is a practicing nephrologist in Houston , TX . Dr. Fadem also serves as a member of the AAKP Medical Advisory Board and Board of Directors. Paul Garney, MS, RD and Bruce Smith, MS, RD are dietitians at Davita Med-Center in Houston , TX .
This article was first published in the May 2002 issue ofaakpRENALIFE.
The information contained herein is intended for educational purposes only. It is not intended and should not be construed as the delivery of medical care. Persons requiring diagnosis or treatment, or those with specific questions, are urged to contact their local healthcare provider for appropriate care.
This article originally appeared in the March/April 2003 issue of Kidney Beginnings: The Magazine, Vol. 2, No. 1.
