Two extracts from shiitake (“woodear”) mushrooms act as immune system stimulators and possess antiviral activities, according to scientists in Japan. LEM, an extract from immature shiitakes, and lentinan, which is an extract from the mushroom’s fruit body, both appear to stimulate immune responses but differ in their antiviral properties.
LEM (for Lentinus edodes mycelium, the Latin name of the immature form of the fungus) is being studied by Dr. Naoki Yamamoto’s research team at Yamaguchi University in Tokyo. These researchers report that a low concentration of LEM inhibits growth of viral diseases in the test tube, and that their studies have “also confirmed that LEM is effective in restoring and bolstering immune response.”
“LEM appears to act on the immune system by stimulating lymphocytes and macrophages, which are responsible for the immune system’s defense against bacteria, viruses, tumor cells, and toxins.”
This preliminary information was provided to the Native by Dr. Tim M. Sharon of El Toro California. Dr. Sharon holds a Ph.D. in theoretical physics, and works in medical instrumentation development. Although not a biologist, he works closely with biological and medical scientists in developing medical instrumentation.
LEM appears to act on the immune system by stimulating lymphocytes and macrophages, which are responsible for the immune system’s defense against bacteria, viruses, tumor cells, and toxins. LEM has also been shown to be effective in stimulating production of antibodies to hepatitis B, and improving liver function.
“LEM—due to its stimulation of immune response—may also improve or restore the body’s immune system when it has been weakened following chronic illness, long periods of stress, medical treatments involving radiotherapy and chemotherapy, or even simple aging, say researchers,” according to Dr. Sharon. “Significantly, laboratory studies point to LEM’s potential ability to suppress liver cancer in early stages of development (when chemically induced in rats) and to inhibit the spread of cancer to other organs.”
Sharon also said, in a telephone interview, that there is some preliminary evidence (primarily from laboratories in Japan) that LEM may interfere with reverse transcriptase activity (a step in the replication of viruses), block receptor sites of viruses on cells, and stimulate IL-1 activity (an immune-modulator important to a healthy immune response). In tobacco plants, LEM is reported to inhibit the spread of mosaic virus, possibly by blocking the receptor site.
Dr. S. Nagaoka, of LEM Laboratory in Tokyo, has patented the process for extracting LEM. The mushrooms used for this process are grown under “Strict environmental control” by the M.O.N. Company in Tokyo, of which Dr. Nagaoka is a cofounder. LEM is taken orally, and is a common food supplement in Japan.
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The antiviral and immune-stimulating results of LEM have so far been demonstrated only in test tube experiments or laboratory animals. However, studies are currently beginning which will investigate the antiviral and immunopotentiating properties of LEM on “viral illness” patients in Japan.
Lentinan, the other shiitake extract, is classified as a drug (rather than as an over-the-counter food supplement like LEM). Lentinan is extracted from the adult fruit body of the mushroom, and does not appear to possess antiviral properties as strongly as LEM. In the laboratory, however, lentinan seems to have the same ability to stimulate the immune system as LEM. Lentinan must be administered intravenously or by injection because it is vulnerable to enzymes in the human digestive system. Lentinan has been under investigation as an immune system stimulator since 1969. More recently, Dr. Tadao Aoki and colleagues at Shinrakuen Hospital in Niigata, Japan, in collaboration with Dr. Ronald B. Herberman at the Pittsburgh Cancer Institute, studied the effect of lentinan on 23 Japanese patients identified as having “low natural killer syndrome” (LNKS).
These investigators describe LNKS as a “newly proposed category of immune disorders,” consisting of lowered NK cell activity (natural killer cells attack other cells infected with viruses or bacteria), remittent fever, and uncomfortable fatigue (defined as exhaustion accompanied by decreased interest in mental and physical activities) that persists “without explanation” for more than six months. Dr. Aoki and colleagues differentiated LNKS from “EBV-associated disease” because their LNKS patients exhibited neither high EBV antibody titers nor the sore throat and painful lymph nodes associated with “EBV disease.” However, their research was performed before publication of the Centers for Disease Control case definition of Chronic Fatigue Syndrome (CFS) in 1988; it seems reasonable to assume that these LNKS patients could be a subset of CFS patients, given the varied presentation and symptomatology of that illness. CFS patients also exhibit low NK cell activity, recurrent fever, and “uncomfortable” fatigue, and a duration of six months is required to receive a diagnosis of CFS.
“If a virus is the cause of LNKS,” write Dr. Aoki and colleagues “it may be a new unknown virus or unknown substrain of known viruses.” They note that “Because of the lack of a definite diagnosis, most of the patients had visited several physicians and hospitals. They were sometimes considered to have psychiatric depression or neurosis and some patients were treated with anti-depressive drugs.”
THE LNKS patients were treated with one milligram of lentinan per day, administered either every other day or twice a week, intravenously or by intramuscular injection. Lentinan was supplied by Aijnomoto, C. In Tokyo, Japan.
These researchers conclude that the “association between the abnormal immunologic profile and the symptomatology was supported” by the improvement in symptoms seen after treatment by lentinan.
“The return to a feeling of well-being and a disappearance of fever usually is seen after 2-4 weeks of treatment. Administration of lentinan then needed to be continued for a prolonged period and was only gradually decreased, after several months of treatment, in order to avoid recurrence of the clinical features of LNKS…Only after continued administration of lentinan to the LNKS (patients) for six months or more did the NK activity return to the normal range.”
It is reasonable to suppose that research on shiitake mushroom extracts would begin again, particularly if both lentinan and LEM are used in clinical trials in the near future. It should be particularly easy to gather data on the efficacy of LEM, because of its availability as an over-the-counter food supplement. The potential of both of these compounds for controlling CFS appears to be greater than any pharmaceutical currently in use.
This article is reprinted from a previous issue of Healthwatch with permission from The New York Native and Neenyah Ostrom, July 31, 1989. We felt it deserved further consideration.