Herbal Therapy

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For thousands of years, plants have been a source of medicinal agents. Many of the drugs we use today still come from plants, for example, morphine (opium poppy), digoxin (foxglove), and atropine (datura) to mention a few.

In recent years, there has been much interest on the part of the general public about herbalism, often as part of an alternative/ complementary form of health care. A renewed interest in herbal remedies and natural products has placed additional responsibility on consumers and health professionals to know:

  • why common medicinal herbs are used;
  • the potential for undesirable side effects, interactions, or allergic reactions;
  • if the claims being made are correct;
  • the quality of available products; and
  • if the cost is reasonable.

The attraction of herbal/natural remedies reflects on interest in a "back to nature" philosophy. While attractive, it is important for the public to know that there may be problems associated with the use of some herbs. For example:

  • "If it is natural, then it must be safe." Strychnine, a natural product once used in tonics, is a violent poison. Tobacco has been positively linked to lung cancer.
  • "Herbs are not drugs." Oregano added to pasta for flavoring is a herb, but the opium poppy, also an herb, contains the very powerful drug morphine.
  • "Herbs cannot do any harm, they can only cure." This is clearly incorrect when you consider plants such as poison ivy!
  • "If it has been used for centuries it must work." The age of a statement is not proof it is correct. Bloodletting was used for centuries, but that did not make it effective. The effectiveness of medicinal agents, whether herbal/natural or man-made, old or new, must be determined through careful study.

Nevertheless, there is a trend toward the use of herbal products to treat just about any condition. A maze of herbal/natural products ranging from vitamins to cancer treatments promoted by advertising is available to consumers. It becomes important to ask about the content, regulation, efficacy, uses, and safety of these products. What do these herbal products contain? How much? What are they used for? How long should they be taken? Are they safe? Do they really work? Are there active chemical ingredients? What are the dosages and warnings for a given herbal/natural product?

How are herbal/natural products regulated?

The difference between herbal/natural products and approved drugs is their regulatory status. Prescription products (for example, morphine) and nonprescription or over-the-counter (OTC products such as senna tablets) must meet strict requirements. The manufacturer must provide:

  • scientific evidence to prove that the product is safe and effective;
  • proof that it follows good manufacturing practices (GMP) in a clean (sanitary) facility that meets all the quality control standards set by the Food and Drugs Administration (FDA) in the United States or Health Canada in Canada; and
  • full label disclosure to indicate medicinal and nonmedicinal ingredients and directions for safe use that include cautions and contraindications.

Scientific evidence requires that the product undergoes careful scrutiny to see whether it is of benefit in treating or curing a given medical condition. This involves treating people in a carefully designed and controlled study that is monitored by health professions to see whether the product is safe and whether it works (i.e., is effective). These studies are referred to as double-blind placebo-controlled clinical trials. This is how researchers determine the effects, side effects, and adverse reactions of a product. If the product is shown to be of benefit, the information or evidence from the study is forwarded to the FDA for further scrutiny and approval for marketing.

If the product is deemed safe, effective, and compliant, it receives a unique Drug Identification Number (DIN) that is clearly printed on the product label. This allows the public to know that they are consuming a product that has been evaluated as being safe and effective for a given medical condition.

In the United States most herbs are sold as "dietary supplements" under the Dietary Supplement Health and Education Act (DSHEA) of 1994. Under this law they are considered safe, unless proven unsafe by the FDA. In other words, the manufacturer does not have to prove the product is safe. Rather, it is up to the government to prove the product is harmful. This is in contrast to prescription and nonprescription products that must be proven safe and effective by the manufacturer before they are marketed.

The DSHEA prohibits making medical claims on dietary supplement labels, but it allows for publications to be used in connection with their sale. Therefore, products are required to bear the words "This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease." The FDA does not scrutinize dietary supplements or literature used to promote their sale. This waiver serves to warn the public that the product or literature has not been approved as a regulated drug.

With a similar twist, in Canada most herbs are sold as a "food" without any labeled disclosure, health claim, or quality control. Marketing a product with a health claim places it under the category of "drug." This would require meeting strict requirements under the "drug" part of the Food and Drugs Act of 1953. Selling it as a "food" avoids any testing for safety and efficacy. Unfortunately, this leaves all consumers and health professionals wondering about the quality, safety, and efficacy of the product.

What kinds of products are we concerned about?

Chronic conditions such as Alzheimer's disease, arthritis, high blood pressure, depression and problems with the prostate gland become more common with advancing age. Consequently products such as, ginkgo biloba, glucosamine, garlic, St. John's Wort and saw palmetto, are frequently promoted as treatments for these health problems.

Ginkgo biloba , L. (Ginkgoaceae). Ginkgo has been prescribed in Europe for illnesses associated with reduced blood flow in the brain in elderly persons. These include depression, short-term memory loss, ringing in the ears (tinnitus), and Raynaud's disease.

Researchers are still studying ginkgo to find out how it works. It may work as an anticoagulant (blood thinner), vasodilator (opens up blood vessels) or as an antioxidant (a chemical that has a protecting effect in the body) (Desmet). The anti-stress and anti-anxiety activity may be due to its effect on an enzyme in the brain (White, Scates, and Cooper; Letzel, Haan, and Feil).

Because of the way ginkgo may work, patients taking aspirin, anticoagulants (blood thinners, for example, Coumadin®), vasodilating agents (drugs that open up blood vessels), anti-inflammatory, or antidepressant drugs should not add ginkgo to their medicines without first consulting with their doctors. Side effects of ginkgo have included stomach upsets, headache, dizziness, and vertigo. Ginkgo seeds and fruit pulp are toxic if eaten (Pharmacist's Letter ).

Clinical studies in humans for symptoms associated with decreased blood flow to the brain, used dosages of 120 to 160 mg per day of a ginkgo biloba extract, with treatment lasting for at least four to six weeks. Results showed that ginkgo may have some benefit but that this needs to be studied further. Ginkgo does not seem to be of benefit for treating tinnitus (World Health Organization).

Glucosamine. Glucosamine is a sugar derivative that occurs naturally in the body (see Figure 1). It is an essential nutrient used in the formation of specialized sugar polymers called glycosaminoglycans. These polymers are used to form bone, cartilage, heart valves, ligaments, nails, tendons, and synovial fluid (a lubricating fluid found in weight-bearing joints).

As the human body ages, cartilage, which cushions the ends of bones, begins to lose elasticity, shrinks, and cracks. Sometimes pieces of cartilage break off into joint space and irritate the surrounding tissue. This inhibits movement and causes inflammation that results in decreased movement and pain. The muscles that hold the joints together weaken due to their lack of use, and the joint may change its shape and function. After a long period the bones may rub together causing more pain and the formation of spurs. This condition is known as osteoarthritis (OA).

It has therefore been suggested that supplementation with glucosamine may relieve symptoms of OA. The usual oral dosage reported in the scientific literature is 500 mg, three times a day. Glucosamine is a by-product of the shellfish industry and obtained from the exoskeletons of crustaceans (lobsters). Pharmacists and physicians should ask the consumer if they have any allergies to shellfish. Glucosamine is well tolerated and adverse reactions or drug interactions have not been reported.

Large-scale, long-term clinical studies are needed to evaluate the efficacy of glucosamine in the treatment of OA (McAlindon et al.). It is important for the patient to understand the nature of OA, risk factors (heredity, injury to the joint, and excess body weight), and current therapy, which includes diet, exercise, and physiotherapy. Appropriate lifestyle changes may eliminate or limit the need for medications.

Serenoa repens (Bart.) or saw palmetto. In men the urethra is surrounded near its base by the prostate gland, which secretes part of the semen. When this gland enlarges, as it often does in older men, urination may become difficult. Symptoms of urinary frequency, urgency, and hesitancy are common in urinary tract infections, cancer of the prostate, or prostate enlargement. Therefore, it is very important for patients to see their doctor to find out the nature of the underlying problem.

Saw palmetto extract, has been used to treat symptoms associated with prostate enlargement ("Sabal fructus"). Clinical studies using an oral dose of 160 mg of extract twice daily indicate that it may help the symptoms associated with an enlarged prostate (Brinker). The most common adverse effects are nausea and stomach pain. Headache, increased blood pressure, urinary retention, and back pain have been reported (Nemecz).

Saw palmetto has not been shown to reduce enlargement of the prostate gland, and patients with symptoms should be encouraged to see their physician for routine checkups.


A herbal/natural product can have effects and side effects. It is best for individuals to check with their doctor or pharmacist to see whether it is safe and effective for them. Individuals should use the same caution as they would with any medication, by consulting their pharmacist or doctor.

Meera B. Thadani

See also Arthritis; Drugs and Arthritis; Evidence-Based Medicine; Prostate; Vitamins.


Brinker, F. "An Overview of Conventional, Experimental and Botanical Treatments of Non-malignant Prostate Conditions." British Journal of Phytoerhapy 3, no. 4 (1993/1994): 156176.

DeSmet, P. A. G. M. Adverse Effects of Herbal Drugs, vol. 3, Berlin: Springer Verlag, 1997.

Letzel, H.; Haan J.; and Feil, W. B. "Nootropics: Efficacy and Tolerability of Products from Three Active Substance Classes." Journal of Drug Development and Clinical Practice 8, no. 2 (1996): 7794.

McAlindon, T. E.; Lavalley, M. P.; Gulin, J. P.; et al. "Glucosamine and Chondroitin for Treatment of Osteoarthritis: A Systematic Quality Assessment and Meta-Analysis." Journal of the American Medical Association 283 (2000): 14691475.

Nemecz, G. "Saw Palmetto." U.S. Pharmacist (January 1998): 97102.

Pharmacist's Letter No. 97-005, Vol. 97, no. 4, Therapeutic Research Centre, Stockton, Calif.: 1997.

Schulz, V.; Hansel, R.; and Tyler, V. E. Rational Phytopathy: A Physicians' Guide to Herbal Medicine. Berlin: Springer-Verlag, 1998.

White, H. L.; Scates, P. W.; and Cooper, B. R. "Extracts of Ginkgo Biloba Leaves Inhibit Monoamine Oxidase." Life Sciences 58, no. 16 (March 1996): 13151321.

World Health Organization. "Ginkgo." World Health Organization Monographs on Selected Medicinal Plants, vol. 1. Geneva, Switzerland (1999): 154167.