A chemical extract from an oriental mushroom has proven to be an effective "vaccine" against cancer in mice.
A study at the National University of Singapore has found that laboratory animals fed lentinan taken from shiitake mushrooms were protected against developing tumours.
The fungi, available in UK supermarkets, are widely used in traditional Asian medicine.
Lentinan's beneficial properties have been known for 30 years. It is sold as a health supplement and used in some Japanese and Korean hospitals in conjunction with chemotherapy. Nevertheless, its appeal has been limited by its high cost and the fact that it has been administered by injection.
Mary Ng Mah Lee, associate professor of microbiology, and colleague A. T. Yap, have devised a way of extracting lentinan that produces a 100-fold increase in yield.
Furthermore, the scientists have shown for the first time that the chemical can imbue significant protection against cancer when taken orally.
The team fed mice 3mg of lentinan a day for a week before attempting to induce tumour.
In 95 per cent, tumour growth was prevented and the animals remained healthy for several months. Even when fed mashed shiitake mushrooms rather than the chemical extract, 55 per cent did not develop tumours.
In a separate experiment, the scientists gave mice lentinan and cancer cells simultaneously. This time, 80 per cent remained tumour free.
Electron microscopy studies have indicated that the immune system was boosted by the lentinan to induce tumour cells to self destruct.
"We are confident that it should work in humans and could be a good immune booster for sick people in general," Dr Ng Mah Lee said.
The findings will be revealed at the International Mycological Congress in Oslo next week.