Goldenseal: The Golden Cure for Common Colds?
August 1, 1998
Dr. Diehl is Associate Professor of Medicine at UCLA School of Medicine, Department of Medicine, Olive View-UCLA Medical Center.
Goldenseal: The Golden Cure for Common Colds?
August 1998; Volume 1: 90-93
By Dónal P. O'Mathúna, PhD
If your patients use herbal remedies, there's a good chance they may be taking goldenseal. A survey in one urban emergency room found it to be the most frequently used herbal preparation.1 Goldenseal is viewed as a powerful natural antibiotic, recommended especially for colds and flu. It reportedly enhances the effects of echinacea, another popular herbal cold remedy2 and is frequently added to other herbal preparations. One web site selling goldenseal claims, "Goldenseal is a cure-all type of herb that strengthens the immune system, acts as an antibiotic, has anti-inflammatory and antibacterial properties, potentiates insulin, and cleanses vital organs. It promotes the functioning capacity of the heart, the lymphatic and respiratory system, the liver, the spleen, the pancreas, and the colon."3
History and Folklore
Goldenseal grows naturally in the woodland areas across much of the Eastern and Midwestern United States, especially in Indiana, Kentucky, Ohio, and West Virginia. It is difficult to cultivate. Its botanical name is Hydrastis canadensis L.; it is part of the buttercup family. It is a low-growing herbaceous perennial, characterized by a bright yellow rhizome (or underground thickened stem), from which it gets its name. Other common names include golden root, eye root, and ground raspberry, because of its red fruit.
Native American tribes commonly used this herb as a diuretic and stimulant, to treat stomach ulcers, and as a wash for irritated eyes and mouth sores. Goldenseal was also an important dye. It was first mentioned by settlers in 1804 as a powerful "bitter" to increase appetite and facilitate digestion, and as a mouth and eye wash.4 Goldenseal was enthusiastically promoted by the Eclectic medical doctors, who focused on herbal remedies and gave many American herbs their first scientific evaluations by carefully observing and recording their effects.4 Many were critical of goldenseal's overblown claims, such as its ability to cure cancer, a claim regarded in 1922 by one Eclectic physician as "folly."5
Goldenseal was officially approved as a medicinal herb in the United States Pharmacopoeia (1830-1840 and 1860-1926), and in the National Formulary (1888 and 1936-1955).4 Many pharmaceutical companies sold the root and preparations of it until the early twentieth century. With the decline of the Eclectics in the 1930s, goldenseal's use dropped off in the United States. Recent interest in goldenseal began when it was reported during the 1970s that its use orally would conceal morphine in drug urinalysis. These claims have been shown to be without scientific merit, but they persist and have even been broadened to apply to marijuana and cocaine.6
Pharmacology
The active ingredients in goldenseal are a group of benzylisoquinoline alkaloids, the most abundant of which are berberine and hydrastine. Alkaloids are a diverse group of alkaline nitrogen-containing compounds made by many plants from a small group of amino acids. Many have pharmacological activity. Berberine, responsible for goldenseal's yellow color, is shown in the Figure in its chloride salt form. Although some attribute all goldenseal's alleged medicinal effects to berberine, the role of each constituent has not been investigated.
Mechanism of Action
The mode of action of goldenseal, and berberine, is not understood. Its GI effects are usually attributed to changes in the mucous membranes. Goldenseal is what herbalists call an alterative, a substance that gradually produces beneficial changes in the body by stimulating natural healing processes. Goldenseal's GI effects are thus said to result from "increasing deficient flow but decreasing excessive flow" of various mucous secretions.7
Bergner claims that goldenseal relieves colds and flu by increasing the flow of mucous, releasing more antibodies.7 Duke states it acts by increasing the blood supply to the spleen, thereby activating the immune system and increasing production of white blood cells.8 A search of MEDLINE and International Pharmaceutical Abstracts (using the terms goldenseal, golden seal, hydrastis, and berberine) revealed no studies to support the mechanistic claims.
Clinical Studies
Clinical studies of berberine, but not goldenseal, do exist. Berberine is also found in a number of other herbs with antimicrobial reputations used as stomach tonics, including barberry, Oregon grape root, goldenthread, and a number of Chinese herbs. Berberine has in vitro antimicrobial activity against a wide variety of Bacillus, Streptococcus, and Candida organisms.9 A number of studies in India found berberine active against Vibrio cholerae, protozoa, and fungi.10 A study with children found berberine (10 mg/kg/d for 10 days) as effective as metronidazole in the treatment of amoebal giardiasis.10 Another study with adults found that a single dose of 400 mg berberine sulfate reduced diarrhea volume due to enterotoxigenic E. coli by 48%, significantly better than control (P < 0.05).11 Significant differences were not found in more severe cholera cases.
However, there are problems relating these effects of berberine to those of goldenseal, especially when the herb is taken orally for colds and flu. Antiviral activity has not been reported for berberine. In animal models, it is poorly absorbed across the intestinal wall.12 In addition, goldenseal contains about 2-4% of berberine, thus requiring 26 commercial goldenseal capsules to obtain the 400 mg dose given in the above diarrhea study, according to Bergner.7 This far exceeds the normal recommended dose, questioning whether it is reasonable to expect a systemic antibiotic effect.
One study may support goldenseal's effect on mucous membranes and, thereby, its relief of some cold symptoms. Mice with drug-induced diabetes were fed a diet containing 6.25% by weight of goldenseal to investigate the claim that it is an effective natural diabetes treatment. No significant changes in plasma glucose and insulin concentrations were detected, but hyperphagia and polydipsia were significantly reduced.13
Formulation
Goldenseal is available as dried root and rhizome in capsules and as a tincture, extracts, tablets, salves, and ointments. For colds and flu, one or two capsules are recommended 2-3 times daily. Alternatively, a tea can be made by adding one teaspoonful of herb (2 or 3 capsules) or tincture to a cup of boiling water. This is usually taken three times daily. Stronger mixtures are recommended for external use only. Given the natural variability of herbal constituents and the problem of adulteration (see below), it is difficult to know how much berberine is contained in these doses.
Adulteration
Widespread use of goldenseal has led to over-collection of the plant, increasingly rare and even extinct in its natural habitats. Cultivation has not been successful. Prices have increased to $100 per pound, leading to adulteration of some preparations by less expensive berberine-containing herbs such as goldthread and Oregon grape.14 Herbalists report these species have different effects.7 A poison center in Utah included Oregon grape (Berberis aquifolium) on its list of plants frequently requiring attention.15 The European Union's drug regulating agency in 1996 listed the closely related Berberis vulgaris as an Herbal Drug with Serious Risks because of its berberine content.7
Adverse Effects
Although detailed studies were not found, herbalists caution that large doses of goldenseal or prolonged use causes adverse effects. Symptoms include nausea, vomiting, paresthesia, hypertension, and respiratory failure; fatalities have been reported.16 Goldenseal (10 capsules; strength not reported) is one of several berberine-containing herbs used as abortifacients, and thus should not be used during pregnancy.7 One herbalist cautions that using one-third of an ounce of dried goldenseal is equivalent to one-tenth of berberine's LD50 and will cause miscarriages.
Berberine also displaces serum-bound bilirubin, raising blood levels and increasing the risk of brain damage in infants with previously raised bilirubin levels.17 This is particularly problematic in Chinese communities, which have a higher prevalence of glucose-6-phosphate dehydrogenase deficiency, and in which herbs (including those containing berberine) are commonly used as a treatment for jaundice and as a postpartum tonic.18
One physician reports observing lowered WBC counts in his patients who use goldenseal for prolonged periods.19
Conclusion
The likely active ingredient in goldenseal has in vitro antibacterial, antifungal, and anti-parasitic activity. However, its systemic efficacy, especially against viral infections, remains unproven. Given reports of serious adverse effects, its popular use for colds and flu appears unwarranted. Goldenseal certainly should not be used during pregnancy or lactation. Ironically, goldenseal has fallen prey to the same tendency toward overuse as have prescription antibiotics, resulting in the plant species' endangerment.
References