Fish oil supplements linked to reduced risk of breast cancer

Scientists found that women who regularly took the supplements reduced their risk of the disease by 32 per cent, nearly a third.

The effect was restricted to invasive duct breast cancer, the most common form.

Other supplements commonly taken by women for menopausal symptoms did not appear to offer any protection.

It is the first time a link has been found between fish oil supplements and reduced breast cancer risk.

Studies looking at whether dietary consumption of fish or omega-3 fatty acids has any impact on breast cancer have been inconclusive.

"It may be that the amount of omega-3 fatty acids in fish oil supplements are higher than most people would typically get from their diet," said lead researcher Dr Emily White, from the Fred Hutchinson Cancer Research Centre in Seattle, Washington.

The Vitamins and Lifestyle (Vital) study recruited 35,000 post-menopausal women who had no history of breast cancer.

All were asked to fill out a 24-page questionnaire about their use of dietary supplements and monitored for six years.

Over that period, 880 of the women went on to develop breast cancer.

The new findings were published today in the journal Cancer Epidemiology, Biomarkers & Prevention.

Dr White said women should treat the results with caution.

"Without confirming studies specifically addressing this, we should not draw any conclusions about a causal relationship," she said.

A US nutrition expert at the Harvard School of Public Health in Boston, Prof Edward Giovannucci, who is also a member of the journal's editorial board, said: "It is very rare that a single study should be used to make a broad recommendation. Over a period of time, as the studies confirm each other, we can start to make recommendations."

Fish oil is already said to combat heart disease, reduce the symptoms of arthritis, and improve brain health. Harvard researchers are now recruiting patients for a new trial which will assess the impact of fish oil supplements and vitamin D on cancer, heart disease and stroke.

The researchers also looked at the effect of other non-vitamin and non-mineral supplements including grapeseed, black cohosh, dong quai, soy, St John's wort, ginkgo biloba, ginseng and melatonin. No association between taking these substances and a reduced risk of breast cancer was seen.

Dietary intake of omega-3 fatty acids and fish has been shown to lower blood concentrations of two inflammation-linked proteins that have been associated with breast cancer.

The scientists wrote: "Animal and human studies support fish oil as having anti-inflammatory and possibly other properties that could reduce breast cancer risk."