The most commonly consumed mushroom-a popular addition to pizzas and pasta dishes-is showing promise for fighting cancer, recent research shows.
White button mushrooms (Agaricus bisporus) contain powerful polysaccharides that are known for their immune-system regulating and antitumour effects. Now, scientists have discovered that they have an ability to stop and even reverse the growth of breast-cancer cells (J Med Food, 2012; 15: 58-65).
In a laboratory study by Arizona State University researchers, extracts of white button and other common mushrooms, including crimini and oyster mushrooms, reduced the growth of human breast-cancer cells by up to 33 per cent (Exp Biol Med [Maywood], 2010; 235: 1306-14).
In animals, white button mushroom extracts have been found to suppress aromatase activity and oestrogen bio-synthesis-important factors in breast-cancer development (Cancer Res, 2006; 66: 12026-34).
But it's not just isolated extracts that have anticancer effects. When white button mush-rooms were added to the diets of mice for 10 weeks, natural-killer (NK)-cell activity was increased. These immune-system cells play a key role in fighting tumours as well as virus-infected cells (J Nutr, 2007; 137: 1472-7).
Although clinical trials are still few on the ground, a recent study of more than 1000 Chinese women reported lower breast-cancer risk among those who ate lots of fresh or dried mushrooms. The most common fresh mush-room eaten was the white button mushroom (Int J Cancer, 2009; 124: 1404-8).
This mushroom appears to be an even more potent cancer-fighter than white buttons. Not only can it suppress the growth of cancer cells, but it can also induce apoptosis-program-med cell death (Exp Biol Med [Maywood], 2010; 235: 1306-14). In one test-tube study, beta-glucan, the polysaccharide found in maitake mushrooms, killed over 95 per cent of prostate-cancer cells (Mol Urol, 2000; 4: 7-13).
Maitake (Grifola frondosa) also appears to be useful for polycystic ovary syndrome (PCOS), in which women fail to ovulate each month or even at all. In a randomized Japanese study of 80 PCOS sufferers, one group received maitake extract, another received the hormone-stimulating drug clomiphene citrate and the third group received a combination of the two. The researchers then followed the patients for up to 12 weeks to compare rates of ovulation. Although maitake wasn't as effective as clomiphene at inducing ovulation (it had a 77-per-cent success rate com-pared with 94 per cent with clomiphene), its lack of side-effects makes it a useful natural alternative. What's more, the combination of maitake and clomiphene induced ovulation in all but two of the 15 patients in that group (J Altern Complement Med, 2010; 16: 1295-9).
Maitake may also have a role to play in controlling diabetes. A powdered form of the mushroom significantly reduced blood sugar levels in mice (Biol Pharm Bull, 1994; 17: 1106-10). In humans, a daily dose of 1000 mg of maitake was found to permanently normalize blood sugar levels in patients who had severe type 2 (non-insulin-dependent) diabetes (Diabet Med, 2001; 18: 1010).
In Japan, the shiitake (Lentinus edodes) poly-saccharide lentinan is approved for use as an anticancer drug. It's considered an important adjuvant treatment for several types of tumours, especially those of the stomach and colorectum.
In one study of advanced stomach cancer, chemotherapy patients who received injections of lentinan once or twice a week in addition to the usual drugs lived significantly longer and had a better quality of life in comparison to the patients who received chemotherapy alone (Hepatogastroenterology, 1999; 46: 2662-8). It appears to work by boosting the immune response by increasing the number of circulating B cells, as demonstrated in a recent clinical trial (Int J Med Mushrooms, 2011; 13: 319-26).
Lentinan may also be a valuable complementary therapy for HIV-positive patients. In a controlled trial of 107 such patients, lentinan taken with the drug didanosine (ddI) increased levels of CD4 cells-among the immune system's main defenses-more than with ddI alone (J Med, 1995; 26: 193-207).
Coriolus versicolor, reishi (Ganoderma lucidum) and especially maitake mushrooms may also have a place in fighting HIV and other viral infections (Life Sci, 1997; 60: PL383-7; Phytochemistry, 1998; 49: 1651-7).
In animal studies, shiitake mushroom powder has been found to lower blood pressure and cut cholesterol, although good (HDL) cholesterol levels were reduced as well the bad (LDL) (J Nutr Sci Vitaminol [Tokyo], 1987; 33: 341-6). These results, however, may not apply to humans.
The reishi mushroom-known in China as lingzhi, the 'plant of immortality'-was recently found to suppress the development of colorectal aden-omas, which are precancerous lesions of the large bowel.
The controlled study investigated the effects of a water-soluble extract of reishi given daily for a year. At the end of the study, the researchers reported that the size and number of adenomas in the reishi group had decreased, whereas adenomas in the control group had increased in both number and size (Hiroshima J Med Sci, 2010; 59: 1-6).
In another clinical trial, reishi extract was significantly better than a placebo at improving lower urinary tract symptoms in men (Asian J Androl, 2008; 10: 777-85).
Other research in humans suggests that reishi may have both antidiabetic and cardioprotective effects (Br J Nutr, 2011: 1-11; Epub ahead of print).
Oyster mushrooms (Pleu-rotus ostreatus) are a natural source of a cholesterol-lowering compound similar to that used in some statin drugs. In dried form, these mushrooms have been shown to significantly reduce cholesterol in animals.
In one study, administering a 5-per-cent dried oyster-mushroom powder to rats reduced blood and liver choles-terol levels by 33 and 27 per cent, respectively (Z Ernah-rungswiss, 1994; 33: 44-50).
Although these results may not apply to humans, one small clinical trial in which 10-15 g/ day of oyster mushrooms were eaten for four weeks reported a 30-per-cent reduction in the participants' LDL cholesterol levels. A larger trial, however, found no significant differences in LDL cholesterol after supplementation with freeze-dried oyster mushrooms in HIV patients with treatment-related high cholesterol (BMC Complement Altern Med. 2011; 11: 60).
The medicinal properties of mushrooms are full of possibil-ities, but the research is still in its early stages. Nevertheless, a number of commercially available mushroom products are already on the shelves.
In general, look for liquid products rather than powdered (dried) supplements, as these are thought to be more bio-available (readily taken up by the body). However, so far, there appears to have been no systematic attempt to evaluate this claim scientifically. It may be that liquid extracts are just more concentrated than the powdered ones.
There is, however, evidence to suggest that using the whole mushroom or mushroom extracts may be more beneficial than supplementing with only its isolated components such as polysaccharides. According to scientists at the University of California at Davis, whole mushrooms contain a number of important active ingredients that may have synergistic actions against disease (Exp Biol Med [Maywood], 2004; 229: 393-406).
Finally, it's worth remem-bering that medicinal and culinary mushrooms are often one and the same, so many of the benefits of mushrooms can be had by simply making them
a routine part of your diet. Research by the US Department of Agriculture has discovered that most of the nutrients in raw mushrooms are fully retained when cooked, while others are retained at levels of 80-95 per cent (www.ars.usda.gov/is/pr/2006/ 060818.htm).
Factfile: Fungal facts
- Because maitake mushrooms are rich in fibre, yet low in calories and fat, they are a potential weight-loss aid. In a study of more than 30 overweight subjects, those who took maitake tablets (equal to consuming 200 g of fresh mushrooms) daily for two months lost weight, despite making no other changes to their usual diets (Altern Med Rev, 2001; 6: 48-60).
- Japanese researchers have found that eating raw mushrooms can eliminate bad breath. Button, field and birch bolete mushrooms were among those with the highest ability to 'capture' methyl mercaptan, the main chemical responsible for halitosis (J Agric Food Chem, 2001; 49: 5509-14).
- A Norwegian study concluded that an extract of Agaricus blazei Murill, an edible mushroom from Brazil, can both treat and prevent bacterial infections such as otitis media, bronchitis, pneumonia and meningitis (Scand J Immunol, 2005; 62: 393-8).
- Fungus-based materials may make good artificial skin and wound coverings. The idea came from similar products based on crustacean shells and the fact that fungal cell walls also contain chitin and/or chitosan. Indeed, Sacchachitin, a skin-substitute membrane prepared from the waste residues of Ganoderma tsugae (hemlock reishi) fruiting bodies, can enhance skin wound-healing in both animals and humans (J Biomed Mater Res A, 2005; 72: 220-7).
WDDTY VOL 22 NO 11, February 2012