The magic and medicine of the mushroom
The Irish Times
Health Supplement, p. 13
6 May 2008
DOES IT WORK? MUSHROOMS HAVE a long history as medicinal agents. Reishi mushrooms have been recommended as a general tonic in traditional Chinese medicine for thousands of years.
Shiitake mushrooms have been used in Japan to stimulate the immune system. “Magic mushrooms” are known for their psychedelic effects, while “death cap” mushrooms remind us that some mushrooms are toxic. All attest to the potent pharmacological agents present in some mushrooms.
One particular mushroom has been attracting much attention for the prevention and treatment of cancer. It was originally discovered in Brazil where its common name meant “mushroom of God” or “mushroom of life”. Japanese researchers brought it to Japan – where it is called Himematsutake – in the 1960s. Its scientific name is Agaricus blazei Murrill, commonly abbreviated as ABM.
Its reputation against cancer has made ABM one of the most widely used medicinal mushrooms in Asia and South America. About half a million people in Japan are believed to use an extract of the mushrooms to prevent cancer or supplement chemotherapy. Surveys have found that ABM is the most commonly used “health food” by Japanese cancer patients. Word of this interest is making its way to Europe and the US where manufacturers are marketing ABM dietary supplements on the basis of Japanese research.
Evidence from studies
Much Japanese research has focused on identifying the active ingredients in ABM extracts. Several “beta-glucans” have been found, which are known to stimulate the body’s immune defence systems.
Several lab studies have verified that ABM extracts stimulate these cells. This has been shown to prevent the spread of some types of cancer cells in animals. ABM extracts do not usually affect cancer cells directly.
While such developments are encouraging, they fall far short of demonstrating that ABM prevents or treats cancer. Few animal studies have been conducted and no clinical trials in humans. The only studies currently available are surveys where patients using ABM report that the extracts helped them and had few side effects. While helpful, these do not show whether ABM is effective.
The mushrooms themselves remain difficult and expensive to grow and process, leading to much diversity in the products available on the market. The amount and variety of beta-glucans vary considerably depending on when they are harvested.
Of more concern is that ABM contains agaritine, a substance known to be toxic and carcinogenic in animals. The agaritine level varies in different extracts, with one product being voluntarily taken off the market in Japan when it was found to have excessive levels of agaritine. ABM extract has been shown to interfere with liver enzymes that break down other drugs. ABM is thus very likely to interact with other drugs that a person might be taking.
ABM mushrooms and their extracts are a good example of a natural product that may lead to useful compounds in the prevention or treatment of cancer. Taxol is an example of one that has become an important anti-cancer drug. But it took nearly 30 years to bring the extract of the Pacific yew to the point of knowing how to safely and effectively use purified taxol in treating cancer.
Much more research is needed on ABM to understand what it contains and how best to use it in people. Some of the compounds may be helpful, but others, like agaritine, are known to be toxic.
Little research has moved past bench experiments, and hardly any research has examined the substances in human trials. As much as we might like to believe that these mushrooms will benefit cancer patients, caution is warranted until evidence is provided to show how this can be done safely and effectively.
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