Two Chinese dietary staples – mushrooms and green tea – may have the power to ward off breast cancer, mounting evidence suggests. A study of over 2,000 Chinese women in the International Journal of Cancer found large quantities of both in the diet slashed cancer risk by up to 90%.

Research suggests chemicals in the foods block tumour growth and boost the body’s natural defences against cancer. But experts say it is unclear whether the benefits will apply to all women. It is known that the rate of breast cancer in China is four- to five-times lower than rates typically seen in developed countries, although this is changing as women are adopting Western diets rich in meat and dairy – and piling on the pounds.

Powerful extracts

Researchers have been hunting for what the Chinese secret might be. Extracts of the mushroom Phellinus linteus have been used for centuries in Easter Ancient medicine where it is believed to refresh bodies and extend life. And scientists in California have been doing a trial to see if taking a mushroom extract twice a day for a month helps breast cancer survivors remain free of the disease after work showed the extract could halt the growth of breast cancer cells.

The new study of Chinese women, by a team at the University of Western Australia in Perth, found that women who ate at least 10g – around a third of an ounce – of fresh mushrooms daily were 64% less likely to develop breast cancer.  Dried mushrooms had a slightly less protective effect, reducing the risk by around half. And women who combined a mushroom diet with regular consumption of green tea saw an even greater benefit.

The risk among women in this group was reduced by almost 90%. Green tea contains antioxidant compounds called polyphenols that have been shown to fight breast tumours in animals. Black tea, although made from the same plant called Camellia sinesis, is not believed to have the same properties because the leaves are processed differently. Black tea leaves go through a fermentation process that strips the plant of its natural polyphenol compounds.

No ’super food’

Researcher Min Zhang and colleagues stressed that their study does not prove cause-and-effect. Although they did account for other known risk factors for breast cancer, such as the women’s weight, education level, and exercise frequency and smoking habits, there could be other factors that explain the findings.

Dr Julie Sharp of Cancer Research UK said: “Both green tea and mushrooms have previously been reported to lower cancer risk and while this study adds to the evidence, more research is needed to confirm these observations and find out if they are relevant to UK women.

“It is important to remember there is no one particular ’super’ food that will protect you from cancer.

“Large scientific studies have proven that the best way to reduce your risk of many cancers is to eat a healthy balanced diet.” Dr Sarah Cant of Breakthrough Breast Cancer said: “Breast cancer incidence rates do vary in different countries and China has lower rates than the UK.

“However, this is likely to be due to cultural and lifestyle differences such as having children earlier or exercising more for example, and is unlikely to be solely due to diet.

“We still aren’t sure which individual food types influence the chance of developing this disease.”

A UK charity said the tea might help men manage low-risk tumours. Although previous studies have shown benefits from drinking green tea – including some positive findings in relation to prostate cancer, there have been mixed results. In this study, Philadelphia-based researchers tested a compound called Polyphenon E.

They were looking for a number of biomarkers – molecules – including vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) which are indicators of developing cancer. They also looked for prostate specific antigen (PSA) – a protein only found in the prostate. Levels can rise if cancer is present.

Polyphenon E (12 cups of tea)

The study included 26 men, aged 41 to 72 years, who had been diagnosed with prostate cancer and who were scheduled for radical prostate surgery. Patients took four capsules containing Polyphenon E for an average of 34 days, up until the day before surgery – the equivalent of around 12 cups of normally brewed concentrated green tea.

The study found a significant reduction in levels of HGF, VEGF and PSA, with some patients demonstrating reductions of more than 30%.

Dr James Cardelli, from the Feist-Weiller Cancer Center, who led the study, said the compound, which was provided by the company Polyphenon Pharma, “may have the potential to lower the incidence and slow the progression of prostate cancer.” There were only a few reported side effects associated with this study, and liver function remained normal.

Dr Cardelli said: “We think that the use of tea polyphenols alone or in combination with other compounds currently used for cancer therapy should be explored as an approach to prevent cancer progression and recurrence.” “There is reasonably good evidence that many cancers are preventable, and our studies using plant-derived substances support the idea that plant compounds found in a healthy diet can play a role in preventing cancer development and progression.”

Active Surveillance

John Neate, chief executive of the Prostate Cancer Charity, said: “There have been several studies into green tea and its potential benefits, but there is, as yet, no conclusive evidence. “The results of this study do suggest that there is merit in further research into the effects of extracts of green tea, both in relation to its impact on the prevention of prostate cancer and in controlling progression in men already diagnosed with the disease, as was investigated in this instance.”

“These initial positive findings could indicate that green tea could have a place in ‘active surveillance’, where a slow-growing, low risk tumour is monitored for changes and men want to take something which could help keep progression at bay. “Potentially, this could mean completely avoiding, in some cases, any of the more usual medical interventions and their associated side effects.”