Breast cancer is the most frequently occurring cancer and the leading cause of cancer death among females; accounting for almost a quarter of total cancer cases and 14% of the cancer deaths. Recent figures show that its incidence is showing no signs of abating, and if proven preventive measures are not implemented fast the diagnosis of new cases over the next decade will hit catastrophic levels.
Now new research has emerged to suggest that when it comes to nutrition advice for thwarting cancer, one food we have erroneously overlooked is oily fish. In the past we have discussed how when it comes to fish oil there is simply no other nutrient that carries its weight with such a consistently supportive evidence base for producing mass reductions in our rampant levels of cardiovascular, inflammatory and mental disease - and generally left it there. But now it's time for the addition of cancer prevention to its resume of impressive benefits.
Published last week in the British Medical Journal was a new meta-analysis of 21 studies of almost one million participants which concluded that consumption of omega 3 fatty acids, as found in fish, produces a significant reduction in the rate of breast cancer occurrence . Those women who consumed the highest levels of fish oil had a 14% lower rate of breast cancer. Considering three quarters of us in the UK do not include oily fish as part of our routine dietary habits, taking the initiative to rectify this would be expected to prevent an astounding 5,000 plus cases of breast cancer, in the UK alone, each year. Indeed, the authors found that upping your intake of fish oil by a mere 100mg a day (achieved by a single portion of salmon a week) reduces breast cancer occurrence by 5%. For those really looking to stamp out any chances of breast cancer from inadequate omega 3 intakes, consumption levels should be targeted to match those we find in Asian cultures (~1 gram of fish oil EPA/DHA a day - achieved safely by consuming a high quality, purity assured supplement).
When we stop to assess the physiological roles of the omega 3 fish oils in the body, it makes sense that their consumption has such a dramatic effect in slashing our cancer risk. Cancer proliferation is greatly encouraged in an inflammatory environment; fish oils inhibit the production of the pro-inflammatory eicosanoids derived from arachidonic acid. Fish oils have also been shown to have direct action in regulating transcription factor activity, gene expression and the activities of molecules involved in controlling the different stages of the cancer cell cycle (growth, differentiation apoptosis, angiogenesis, and metastasis). On top of this, there is evidence that fish oils can decrease the production of oestrogen - an oestrogen imbalance is the primary cause of breast cancer.
It is essential to note that while fish consumption (1-2 servings a week) is perfectly adequate to exert this chemo-preventive effect, it must be in the form of oily fish, such as herring, salmon, trout and mackerel. It is the fish oil specifically that exerts the beneficial effect, meaning white and tinned fish just do not cut it. In addition to this the effects are only observed from consumption of the omega 3s EPA and DHA. The plant derived inferior omega 3 ALA does not confer any protective effect. This means that an algae supplement (which provides marine DHA) is a must for vegans, vegetarians or anyone else who does not consume fish or fish oil supplements.
 Zheng, Ju-Sheng, et al. "Intake of fish and marine n-3 polyunsaturated fatty acids and risk of breast cancer: meta-analysis of data from 21 independent prospective cohort studies." BMJ: British Medical Journal 346.
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