According to the study published on bmj.Com, each 0.1 g per day or 0.1 per cent energy per day increment of intake of n-3 polyunsaturated fatty acid (n-3 PUFA) derived from fish was associated with a 5 per cent reduction in breast cancer risk.
To achieve this risk reduction, intake of oily fish such as salmon, tuna or sardines should be 1-2 portions per person per week.
Researchers from Zhejiang University in China set out to investigate the association between fish and n-3 PUFA intake and the risk of breast cancer. Levels were measured from both dietary sources and blood tests.
Marine n-3 PUFA was associated with a 14 per cent reduction of breast cancer between the highest and lowest category of marine n-3 PUFA intake.
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The risk was lowest in Asian populations, probably because fish intake is much higher in Asia than in western countries, authors said.
The authors said their analysis, together with previous publications, "supports a protective role of marine n-3 PUFA on the incidence of breast cancer."
"Our present study provides solid and robust evidence that marine n-3 PUFA are inversely associated with risk of breast cancer. The protective effect of fish or individual n-3 PUFA warrants further investigation of prospective studies," they said.