Researchers from the University of Copenhagen have found that selenium - naturally found in garlic and broccoli - slows down immune over-response, improving treatment against cancers such as melanoma and prostate cancer.
Melanoma, prostate cancer and certain types of leukaemia weaken the body by over-activating the natural immune system.
The immune system is designed to remove things not normally found in the body.
However, different cancer cells contain mechanisms that block the immune system's ability to recognise them - allowing them to freely continue cancer development.
Stimulating molecules of certain cancer cells over-activate the immune system and cause it to collapse.
"We have now shown that certain selenium compounds which are naturally found in garlic and broccoli effectively block the special immuno-stimulatory molecule that plays a serious role for aggressive cancers such as melanoma, prostate cancer and certain types of leukaemia," said professor Soren Skov from department of veterinary disease biology at the University of Copenhagen in Denmark.
In the long term, this may improve cancer treatment, he added.
"If we can find ways to slow down the over-stimulation, we are on the right track. The new results are yet another small step towards better cancer drugs with fewer adverse effects," Skov said.
The findings have been published in the Journal of Biological Chemistry.