A balanced diet with a variety of vegetables can reduce risk of cancer. REUTERS

Selenium, found in food like garlic and broccoli, can help modify the immune response and fight cancers like melanoma, prostate cancer and certain types of leukaemia, says a study.

Where the cancers over-activate the natural immune system, selenium slows down the same.

Normally, the immune system is trained to remove foreign bodies from the body but cancer cells have mechanisms that help evade detection.

Some cancer cells overexpress immunostimulatory molecules in liquid form. This has a negative impact on the immune system and can even lead to its collapse.

Researchers from the University of Copenhagen focused on one such molecule, the NGK2D ligand, which dissolves and spreads in the blood and becomes a marker for serious illness.

Selenium compounds were seen to have a very beneficial effect when it comes to neutralising the special variant of the NGK2D ligand found in blood and on the surface of the cancer cells.

"We have now shown that certain selenium compounds, which are naturally found in, e.g., garlic and broccoli, effectively block the special immunostimulatory molecule that plays a serious role for aggressive cancers such as melanoma, prostate cancer and certain types of leukaemia," says Professor Søren Skov, Department of Veterinary Disease Biology, University of Copenhagen.

The findings are published in the Journal of Biological Chemistry.

Both garlic and broccoli are popularly advocated in the fight against cancer.

Garlic contains sulphur compounds that may stimulate the immune system's natural defences against cancer. But there is not enough evidence to support eating large amounts of garlic or taking garlic supplements for cancer prevention, says the American Cancer Society.

So also with broccoli which is a source of phytochemicals that may have anticancer properties and could help detoxifying enzymes in the body. The best advice at this time to reduce cancer risk is to eat a wide variety of vegetables, in which broccoli is part of a balanced diet.

Foods containing vitamin D could help lower risk from cancer while eating too much red meat could trigger cancer.