Women who take fish oil supplements may have a lower risk of developing breast cancer than those who don't, a study published on July 08 suggests - though whether the supplement itself bestows the benefit is not yet clear.
In a study of more than 35,000 postmenopausal women, researchers found that those who said they regularly used fish oil supplements were one-third less likely than non-users to develop breast cancer over the next six years.
The lower risk was seen even with a number of known and suspected risk factors for breast cancer taken into account - including older age, obesity, heavy drinking and sedentary lifestyle.
Still, the study is limited in the fact that it is what is known as an "observational" study - where researchers look at the relationship between an "exposure" (like supplement use) and a disease risk.
"There are a lot of cautions with this type of study," said senior researcher Dr Emily White, of the Fred Hutchinson Cancer Research Centre in Seattle. "It cannot show cause-and-effect. "So it is too soon to recommend that postmenopausal women start taking fish oil for the sake of lowering breast cancer risk, White told Reuters Health in an interview.
Any such recommendations may come if and when evidence from clinical trials supports a benefit of fish oil. "Fortunately, there is going to be a clinical trial," White said.She was referring to a Harvard University trial just underway that will look at whether fish oil and vitamin supplements affect the risks of cancer, heart disease and stroke in older men and women.
In that study, which aims to enrol 20,000 U.S. adults, researchers will randomly assign participants to take one or both supplements, or placebo pills to serve as a comparison. This type of study is considered the "gold standard" for demonstrating cause-and-effect.Fish oil, a rich source of healthy fatty acids known as omega-3, is best known as a potential boon for heart health. A number of clinical trials have shown that fish oil may help lower triglycerides (a type of blood fat), high blood pressure and the risk of heart attack in people with established heart disease; high fish consumption has also been linked to a lower risk of developing heart disease.So experts generally recommend that adults aim to eat fish at least twice a week - preferably fattier fish like salmon, mackerel and trout. But whether fish or fish oil have any effects on cancer risk remains unclear.
The new study, published in the journal Cancer Epidemiology, Biomarkers & Prevention, looked at the question by asking 35,016 women ages 50 to 76 about their current and past use of fish oil and certain other supplements.