Mushrooms may protect against cancer
A diet containing lots of mushrooms, such as shiitake and oyster mushrooms, may protect against cancer. A small epidemiological study that South Korean researchers at Hanyang University published in 2008 in the International Journal of Cancer suggests this. We have our reservations about the study, but nevertheless the results seem too good to be true.
The researchers compared the mushroom intake of 362 women aged 30-65 who had breast cancer with that of a comparable group of women without breast cancer. They did statistical gymnastics to filter out the effects of educational level, heredity, physical exercise, BMI, smoking, alcohol, supplements and the intake of folate, vitamin D, kilocalories, carbohydrates and soya protein.
There are indications that mushrooms contain substances that may protect against cancer. Koreans eat relatively large quantities of mushrooms. The types of mushrooms that are most common in the Korean diet are shiitake, oyster mushrooms and winter mushrooms.
Among the premenopausal women, those who ate mushrooms had less breast cancer. The relationship was not statistically significant, though.
The situation was different among the postmenopausal women. The more mushrooms they ate per day, and the more frequently they ate mushrooms, the lower their risk of developing breast cancer.
If the Koreans' calculations are correct, then every 15 g mushroom per day reduces the chance of breast cancer in postmenopausal women by 32 percent.
"Increased dietary intake and consumption frequency of mushrooms may be associated, in a dose-response relationship, with a decreased risk of developing breast cancer in postmenopausal women," the Koreans concluded. "These findings may be helpful in providing recommendations to the public on how to prevent breast cancer, especially in postmenopausal women."
"Further studies on dietary mushrooms among various populations in a large cohort study are needed in order to generate more detailed guidelines about cancer prevention."
A big but
The last sentence above is doubly relevant in the case of this study. "While health related behaviors such as regular exercise, smoking, drinking, multivitamin supplement use, BMI and dietary factors were adjusted for, the residual effects of other health-related behaviors may still have influenced the results," the researchers wrote.
"Given the common belief in Korea that mushrooms are healthy, people who preferred mushrooms would most likely have other healthy dietary habits."
Int J Cancer. 2008 Feb 15;122(4):919-23.
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