Herbal supplements are becoming increasingly popular among consumers. Herbal medicines come in many forms including liquids, tinctures, pills, capsules, tablets, teas and loose herbs. It is generally believed that herbs will do no harm since they are ‘natural’ substances. Although many herbal remedies have shown no ill effects in studies, some others should be used with caution.

About 25% of prescription drugs contain active ingredients from plants i.e. digoxin, morphine. Extracts or parts of plants used for medicinal purposes fall under the herbal remedy category. However, lack of quality control in the growing, harvesting and processing of herbal medicines mean that they may not even contain any active ingredients.


How can one know that the herbal product contains what it says on the label?

Some products list their ingredients in detail while others do not. In Canada, all medicines are issued a Drug Identification Number. Herbal medicines are not required to meet any regulatory standards. The chemical content of plants vary depending on the part of the plant used, species, variety, age and soil conditions. Some herbal medicines have been found to contain other more toxic herbs, metals or drugs.


Are herbs effective as medicines?

Western medicine is based on clinical studies (usually randomized placebo-controlled) that are evidence based. The placebo effect works about 30-40% of the time due to expectation, suggestion and belief. Few herbal medicines have been tested this way, but this article will review some of the recent studies on the effectiveness of herbal remedies. (see table)


Are herbal medicines dangerous?

Some herbal medicines have been found to have adverse effects. These include serious allergic reactions, toxicity, and drug interactions.



Numerous herbal supplements are available on the market and the accompanying table identifies just a few that can be found. Plants are potentially effective medicines and consumers wanting to take such herbal remedies should carefully research information on the products. Consult your physician if you are currently taking or planning to take any herbal medicines.



Study Results

Side Effects

Aloe (ferox or barbadensis) Laxative (daily dose 0.05-0,2g dry extract) Effective laxative; lethal dose 1g/day for several days For acute not chronic constipation, may cause diarrhea, not recommended during pregnancy
Cayenne (Capsicum) Gastrointestinal stimulant. Decreases blood clotting and blood cholesterol Effective as stimulant, but evidence lacking re: clotting, cholesterol Can cause stomach irritation
Chamomile (Chamomillia procumbens) Back pain Some results compared to placebo Allergy
Chaparral Diuretic, pain reliever, bowel cramps, anticancer Evidence lacking Liver toxicity; In 1968, FDA removed it from its GRAS list (‘generally recognized as safe’)
Echinacea (E.pallida, E.purpurea or E.angustifolia) Treatment of flu by enhancing immune function Results vary in studies. Intravenous treatment effective, but questionable results when taken orally as capsule or tea. Allergy
Evening Primrose (oenothera biennis) Premenstrual Syndrome, Ulcerative colitis Results same as placebo
Ephedra (Ma Huang) Decreased appetite, weight loss 20-30 deaths and more than 800 adverse effects attributed to Ephedra High blood pressure and heart rate, People with heart disease and high blood pressure should avoid
Feverfew (Tanacetum parthenium) Migraine Benefit for migraines compared to placebo Allergy
Ginger (zingiber officinale) Nausea, vomiting Found to be effective in 3 studies but same as placebo in 1 study
Ginkgo biloba (EGb) Dementia progression Five studies found effectiveness in slowing dementia progression Bleeding, Interaction with Coumadin and ASA, Avoid if pregnant or nursing
Ginseng, Asian (Panax ginseng) Exercise performance, Flu, immune response Results same as placebo(exercise) One study found benefit when compared with placebo(flu) Skin rash, Headache, Insomnia, Increased blood pressure
Saint John’s Wort (Hypericum per foratum) Antidepressant Two studies found benefit when compared with placebo Skin photosensitivity, Should not be taken with other psychoactive medications

Mary Flesher, Clinical Dietitian
First published in the Inside Tract® newsletter issue 111 – January/February 1999