CHAPTER TEN
Lentinan and HIV
How THE JAPANESE discovered the health benefits of shiitake makes for an interesting story. In the 1960s, Japanese researchers undertook a series of epidemiological studies to learn everything they could about incidences of disease in their country. In the course of one study, they found two remote mountainous districts where cancer was nearly unheard of. The government sent teams of scientists to these districts to find out why cancer rates were so low there. Was it something about how the people lived? Something in the diet? It so happened that growing shiitake mushrooms was the chief industry in both districts. The inhabitants ate a lot of shiitake, apparently believing that it helped prevent cancer.
The shiitake mushroom is delicious. After the white button mushroom, shiitake is the most popular culinary mushroom in the world. The cultivation of shiitake in the United States is increasing faster than the cultivation of any other culinary mushroom. Shiitake is a gourmet delight. The mushroom’s meaty flavor can complement almost any dish and, as it turns out, the mushroom that delights so many with its distinctive flavor is also a medicinal mushroom.
The mushroom is known throughout most of the world by its Japanese name, shiitake (shee-ee-TAH-kay). The name comes from the Japanese word for a variety of chestnut tree, shiia, and the Japanese word for mushroom, take. Shiitake is sometimes called the Forest Mushroom and the Black Forest Mushroom. In China, it is known as Shaingugu (alternate spelling, Shiang-ku), which means “fragrant mushroom.” Shiitake’s Latin name is Lentinula edodes, the etymology of which is as follows: lent means “supple,” inus means “resembling,” and edodes means “edible.” About 1980, a debate concerning shiitake’s Latin name broke out among taxonomists. Without going into all the details, the mushroom’s name was changed from Lentinus edodes to Lentinula edodes. Prior to 1980, literature concerning the shiitake mushroom refers to the name Lentinus edodes.
The shiitake mushroom is native to Japan, China, the Korean peninsula, and other areas of East Asia. The cap is dark brown at first and grows lighter with age. The spores are white and the edges of the gills are ser-rated. In the wild, shiitake grows on dead or dying hardwood trees—chestnut, beech, oak, Japanese alder, mulberry, and others—during the winter and spring. It prefers forest shade where cold water is nearby. The shiitake industry in Japan, as large as it is, can be credited with preserving much of the nation’s forests. Without income from shiitake, many a yeoman farmer would have long ago cut down his trees or sold his land to developers. Shiitake mushrooms are Japan’s leading agricultural export. Japan accounts for eighty percent of worldwide shiitake production.
Even by mushroom standards, shiitake is high in nutrition. The mushroom contains all the essential amino acids, as well as eritadenine, a unique amino acid that some physicians believe lowers cholesterol. Shiitake is high in iron, niacin, and B vitamins, especially B1 and B2. In sun-dried form, it contains vitamin D.
Shiitake cultivation in the United States got off to a slow start, thanks in part to the United States Department of Agriculture. For much of the last century, the USDA imposed a complete quarantine on the importation of shiitakes. USDA bureaucrats imposed the quarantine because they mistook Lentinus edodes (shiitake’s former Latin name; it has since been changed to Lentinula edodes) for another mushroom called Lentinus lepideus. This mushroom—its common name is Train Wrecker—was known to attack and corrode railroad ties. Train Wrecker was the suspect in several railway mishaps. The USDA realized its mistake and lifted the quarantine against shiitakes in 1972. Today, American growers produce approximately five million pounds of Shiitake mushrooms annually.
Historical documents in Japanese archives relate how Chuai, the bellicose fourteenth emperor of Japan, praised the shiitake mushrooms that were given him by members of the barbarian Kumaso tribe, whom he was trying to subdue on the island of Kyushu in the second century. Shiitake is supposed to have been used in the ancient Japanese royal court as an aphrodisiac.
In China, the cultivation of shiitake mushrooms began about a thousand years ago with a woodcutter named Wu San-Kwung in the mountainous areas of Zhejiang Province. To test his axe, Kwung swung it against a fallen log on which shiitake mushrooms grew. Days later, he noticed shiitake mushrooms growing where his axe struck the log. As an experiment, he cut the log in several different places. Once again, shiitake mushrooms grew where his axe landed. In this way, the log method of cultivating mushrooms was born. On one occasion, the story goes, mushrooms failed to grow on a log and Kwung grew frustrated. He attacked the log, beating it vigorously with the blade of his axe. When he returned to the scene of the battering, he discovered to his surprise that the log was covered with mushrooms. Kwung had discovered the “soak and strike” method of mushroom cultivation in which logs are battered in such a way that spores have more openings in which to germinate. This method is still used in some places. Wu San-Kwung’s contributions to agriculture are commemorated in a temple in Qingyuan. Festivals in his name are still celebrated throughout Zhejiang Province.
In traditional Chinese medicine, shiitake is used to treat high cholesterol, atherosclerosis, colds, and flu. The mushroom is also believed to enliven the blood, dispel hunger, and cure the common cold. It is supposed to boost Qi, the primal life-force that animates the body and connects it to the living cosmos. Given the high regard with which shiitake is held, it was only a matter of time before scientists got around to testing its medicinal properties.
In 1969, Tetsuro Ikekawa of Purdue University, working in conjunction with researchers at the National Cancer Center Research Institute in Tokyo, extracted a 1-3 beta glucan from shiitake that he tested on mice that had been infected with tumors. In seventy-two to ninety-two percent of the mice, tumor growth was inhibited. From this study, Lentinan was born (the beta glucan was named for Lentinula edodes). Ikekawa and his colleagues conjectured that Lentinan bolstered the immune system by activating macrophages, T lymphocytes, other immune-system cells, and the production of cytokines.
By 1976, scientists had run Lentinan through clinical trials and pharmaceuticalized it. The Japanese government’s Health and Welfare Ministry, the equivalent of the United States’ Food and Drug Administration (FDA), soon approved the drug and it was put on the market. Almost immediately, Lentinan proved effective in treating many kinds of cancers. However, the drug does not have any direct anticancer activity. When Lentinan is placed in a test tube with cancer cells, it does not affect the cells, but when it is injected into the body, Lentinan triggers the production of T cells and natural killer cells. Lentinan is the third most widely prescribed anticancer drug in the world. Doctors often prescribe it to patients who have undergone chemotherapy as a means of revitalizing the patients’ immune systems. Regrettably, Lentinan has not been approved by the United States’ Food and Drug Administration. Except under special circumstances, it is not available to Americans.
Shortly after the AIDS epidemic began in the early 1980s, physicians began experimenting with Lentinan as a means of making the immune system less susceptible to HIV, the virus that causes AIDS. Lentinan generated a lot of enthusiasm at the Sixth International Conference on AIDS in 1990, when reports were published showing the drug’s ability to increase helper T cells, the cells whose job it is to mark invaders so they can be destroyed by the immune system (HIV destroys helper T cells).
Another substance extracted from shiitake called LEM (Lentinula edodes mycelium) is believed to be helpful against hepatitis B. This disease is transmitted by blood transfusions, nonsterilized needles, and sexual contact. Some studies have shown that LEM stimulates the production of antibodies that counteract hepatitis.
Following are a couple of recent studies that concern shiitake mushrooms. Shiitake is good medicine. Given the popular notion that what tastes good is bad for your health, we wonder if people would find shiitake mushrooms as delicious if they knew how good for their bodies.
Lentinan and AIDS
Aware that a Japanese study showed that cancer patients did not get significant side effects from taking Lentinan, researchers in the United States were curious whether Lentinan could be used to treat AIDS patients. The researchers wanted to know whether Lentinan could strengthen AIDS patients’ immune systems and whether the patients would tolerate Lentinan as well as the Japanese cancer patients had. As we mentioned earlier in this chapter, Lentinan is a 1-3 beta glucan that is extracted from the shiitake mushroom.
The study of AIDS patients was conducted jointly in San Francisco and New York. In San Francisco General Hospital, ten patients were intravenously administered either 2,5, or 10 milligrams of Lentinan or a placebo once a week for eight weeks. At the Community Research Initiative in New York, two groups of twenty patients were intravenously administered either 1 or 5 milligrams of Len tin an twice a week for twelve weeks, and ten patients were administered a placebo. In New York, where the infusion was carried out over a thirty-minute period, no side effects were reported. In San Francisco, where infusion took ten minutes, four patients discontinued therapy because of side effects. Still, most side effects disappeared in twenty-four hours after the medication was discontinued. What’s more, dramatic side effects such as anemia, a drop in white blood cells, or inflammation of the pancreas were not observed.
In all patients who took Lentinan, the number of lymphocytes—the white blood cells that circulate in the lymph and help flush viruses and bacteria from the body—went up. However, researchers cautioned that the small number of patients in the study prohibited them from concluding that Lentinan actually increases activity by lymphocytes. Given the small number of side effects observed in the study and the increase in lymphocytes, researchers recommended undertaking a trial in which Lentinan is used in combination with zidovudine (AZT) or didanosine (a protease inhibitor), two drugs specific for HIV.
A subsequent trial in which the researchers treated some patients with Lentinan and didanosine and other patients with didanosine alone showed a marked increase in lymphocytes in the Lentinan-didanosine patients when compared with those who received only didanosine. These provocative studies suggest that Lentinan can be useful for treating patients with HIV.
Shiitake and Tooth Decay
Dental plaque is a soft, thin, sticky film that forms on the surface of teeth, often near the gum-line. It is made up of millions of bacteria, as well as saliva and other substances, and can cause tooth decay. In case you haven’t heard by now, the best way to prevent plaque from forming on teeth is to brush regularly.
To see if shiitake can help prevent tooth decay, researchers from the Nihon University School of Dentistry in Japan conducted a test in which they exposed the Streptococcus mutans and Streptococcus sobrinus bacteria to shiitake powder. Dentists know these bacteria verywell, because they are the primary components of dental plaque. In an in vitro test, researchers observed a decrease in plaque formation in the test tube. In an in vivo test conducted on laboratory rats that had been infected with Streptococcus mutans, researchers compared rats who had been fed the shiitake extract with rats who did not get the benefit of shiitake. The researchers discovered significantly fewer cavities in the shiitake group. What’s more, the shiitake component of the rats’ diet amounted to only 0.25 percent, which indicates that shiitake may be a potent protection against tooth decay.
In another study undertaken at the Nihon University School of Dentistry, researchers found that shiitake was effective against several bacteria, including varieties of Streptococcus, that are commonly found in the mouth. Generally speaking, the study found that microbes such as Candida that are not found in the mouth were resistant to the mushroom. It appears that as a medical mushroom, shiitake is especially useful to dentists.