The fish oil supplements that millions of men take each day to cut their risk of heart disease might have a negative health effect.

A new study suggests that men who have higher levels of omega-3 polyunsaturated fatty acids in their system face a more than 40 per cent increased risk of developing prostate cancer.

To determine this, the researchers relied on data from a past study that examined the blood concentrations of omega-3 in nearly 850 men with prostate cancer and about 14-hundred men without prostate cancer.

When they did this, the researchers found an association between high omega-3 levels and the occurrence of prostate cancer.