DOES IT WORK? Goldenseal has years of traditional use but very little evidence to support this use, writes Dónal O'Mathúna
GOLDENSEAL HAS been one of the most popular herbs sold in the United States. It is often combined with Echinacea and other herbs as a "natural antibiotic" for the treatment of colds and flu.
Its popularity has waxed and waned over the decades, usually depending on its availability. It was widely used by Native Americans who passed it on to early American settlers. Its natural sources soon became depleted and it faded out of popular use.
During the 1960s, it developed a reputation for masking the presence of illegal drugs in urine tests. This urban myth has been traced to a novel written in 1900 by US pharmacist, John Uri Lloyd. There is no scientific basis to the story.
Nor is there evidence that goldenseal helps for any of the other conditions for which it is popularly recommended. Despite this, it continues to be widely recommended as an alternative to pharmaceutical antibiotics.
Evidence from studies
Laboratory studies have found that goldenseal contains a number of chemicals called alkaloids.
The best-known of these is berberine, which has been found to have some antimicrobial activity in the lab.
However, when tested in animals, an important limitation was found. Only a tiny proportion of the berberine given to animals was absorbed from their intestines. Tests in humans have revealed similar problems.
One study estimated that a person would need to consume 26 capsules of a commercial goldenseal product to absorb enough to have a possible effect.
Since the active ingredients are poorly absorbed, ointments and creams containing goldenseal for skin infections have appeared on the market. No studies have been reported on these uses.
Despite its widespread popularity, goldenseal has not been studied in clinical trials. The small amount of research that has been done on berberine does not support its oral use in humans, and does not lend any support to the use of goldenseal for cold or the flu.
Problematic aspects
Large doses of goldenseal (and other berberine-containing herbs) have been reported as causing abortions. This suggests that goldenseal should not be used during pregnancy, a recommendation supported by many herbalists. Some evidence is also available that newborn babies with jaundice had their symptoms worsened if their mothers took goldenseal while breastfeeding.
Although the evidence is primarily anecdotal, goldenseal should be avoided during pregnancy and breastfeeding.
Goldenseal has been widely used at different times in recent history. Each time its use declined because of limited supply. We are entering such a phase at the moment.
Goldenseal has been overharvested to the point that its wild variety is now listed as an endangered species by some environmental organisations. The problem arises from both harvesting in the wild where plants are not replaced and the destruction of woodlands through mining and deforestation.
The short supply of goldenseal has led to high prices, which in turn have led to the discovery of goldenseal products that contain no goldenseal. Products that list goldenseal as one of several herbs contained in the preparation often do not state how much should be present.
Recommendations
Goldenseal is a herbal remedy that is long in traditional use and short in supporting evidence. Very little relevant research has been carried out. What research has been conducted in the laboratory is generally not supportive of its value for humans.
Given this, and the way the herb has become endangered due to overharvesting, there appears to be no good reason to use goldenseal.
• Dónal OMathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University. He authored Alternative Medicine: The Christian Handbook, Updated and Expanded Edition, Zondervan, 2007