Men with prostate cancer have been boosted by research which indicates their chances of survival may increase if their diet is rich in fish oil fatty acids.
Studies on mice suggest that omega-3 fatty acids, found in oily fish such as mackerel, herring, tuna and sardines, can slow the disease's progress.
Omega-3 in the diet might benefit men with a genetic susceptibility to prostate cancer, and prevent the disease from shortening their lives, scientists believe.
In experiments carried out in the US, mice engineered with a genetic defect that gave them prostate cancer were fed from birth on a diet high in omega-3 fatty acids.
Researchers writing in the Journal of Clinical Investigation said their disease progression was reduced, and survival increased.
Professor Yong Chen, who led the team at Wake Forest University School of Medicine in Winston-Salem, North Carolina, said: "This study clearly shows that diet can tip the balance towards a good or a bad outcome.
"It's possible that a change in diet could mean the difference between dying from the disease and surviving with it."
Dietary changes may especially benefit people prone to prostate cancer because the disease is usually diagnosed in older men, and the tumours grow slowly, Prof Chen said.
He pointed out that a high omega-3 diet could delay tumour development or progression long enough for a man with prostate cancer to live out his normal lifespan.