Subject Categories: Clinical medicine
Published online 7 August 2013
Breast cancer is one of the most common types of cancer, accounting for 23% of cancer cases and 14% of cancer deaths in 2008. Prospective cohort studies in Singapore and Japan have shown that omega-3 fatty acids can help prevent breast cancer. Studies elsewhere, however, have found no association between omega-3 fatty acids and breast cancer risk.
To resolve this controversy, Duo Li and co-workers at Zhejiang University and APCNS Center of Nutrition and Food Safety in Hangzhou have now collated data from 26 publications and aggregated the outcomes of 21 independent prospective cohort studies. They found that only marine omega-3 fatty acids (i.e., those found in salmon, herring and mackerel) have the health benefit of lowering the risk of breast cancer.
The 21 prospective cohort studies encompass 20,905 breast cancer cases and 883,585 participants from countries in North America, Europe and Asia. The researchers studied the effects of fish, marine omega-3 fatty acids (e.g., EPA, DHA and DPA), and plant omega-3 fatty acids (e.g., ALA) separately. They could associate a 14% reduction in breast cancer risk with a high intake of marine omega-3 fatty acids, but not with a high intake of fish or plant omega-3 fatty acids.
The finding not only confirms the protective effect of marine omega-3 fatty acids, but also explains the discrepancy between the results of previous studies. The researchers believe that the low fish content of the Western diet is responsible for the missing association between omega-3 fatty acid intake and lower breast cancer risk.