Mushrooms & Green Tea May Reduce Breast Cancer

Risk Cut More Than Half Among Chinese Users

May 31, 2009

Chinese women who ate fresh or dried mushrooms and drank green tea had much less risk of getting breast cancer, a recent study found.

It’s been generally observed that Chinese women are less likely to get breast cancer than women in other developed countries. It has also been observed that phytochemicals (chemicals in plants that might be useful as medicines) may reduce cancer risk. Researchers wanted to see if consuming phytochemicals might contribute to the reduced breast cancer risk in Chinese. A chemical derived from mushrooms, Polysaccharide-K, is used in Europe, Japan, and China as an adjuvant in cancer therapy, so they selected eating mushrooms to study.

It has also been observed that polyphenols may reduce cancer risk, so green tea, rich in polyphenols, was included in the study.

The Study

About a thousand women (1,009) with newly diagnosed breast cancer were compared to 1,009 other women as controls. The control group was matched person to person by age with the cancer group. All the subjects were seen in a clinic in Hangzhou, China.

Information about diet and tea drinking for the past 30 days was obtained from all the subjects. A multivariate analysis, which attempts to account for other known risk factors, compared those with cancer to those cancer-free.

Results

One group of women had much lower risk of cancer. This group was women who consumed 10 grams (0.35 oz) or more of fresh, or 4 grams (0.14 oz) or more of dried mushrooms, and also consumed more than one gram (0.035 oz) of dried green tea each day. This group compared to non-consumers had less than one fifth (<20%) the risk of breast cancer.

That comparison was the most striking, but there was a trend throughout the results that lower mushroom and tea consumption was associated with higher cancer risk.

Reporting mushroom and tea consumption as weight eliminates differences that might be due to differences in preparation, such as how dilute the tea was. Mushrooms the size of those in the illustration weigh about 20 grams or two thirds an ounce each. A commercial teabag generally contains a little less than two grams dried tea. Reporting consumption as daily intake was calculated from servings over a period of time; for example, one serving of two and a half ounces of mushrooms a week is reported as 2.5/7 or 0.38 oz per day.

Study Limitations

There are several reasons why this study may not be applicable to many women in Canada, the United States, and other non-Chinese countries.

First, only Chinese women were subjects. There may be genetic differences that make the results not applicable.

Second, there may be confounders—characteristics not studied that influence or cause the findings. For example, women who drank no or very little green tea, and ate no or very few mushrooms, may be different in other ways, such as other diet risks or use of estrogen-type herbs or medications.

Third, women with breast cancer at the clinic may have been referred to the clinic from a particular group, and not be representative of the general population. This is called referral bias.

The copyright of the article Mushrooms & Green Tea May Reduce Breast Cancer in Nutrition is owned by James Cooper. Permission to republish Mushrooms & Green Tea May Reduce Breast Cancer in print or online must be granted by the author in writing.