Omega-6 fatty acid intake tied to breast cancer

NEW YORK (Reuters Health) - Substances called heterocyclic amines (HAs) found in cooked meat and fish don’t appear to boost a woman’s risk of developing breast cancer after menopause, Swedish researchers report.

However, low intake of these substances combined with high consumption of omega-6 polyunsaturated fatty acids (PUFAs), which are found in most types of vegetable oil, may indeed increase the likelihood that postmenopausal women will develop breast cancer, Dr. Emily Sonestedt, of Lund University, Malmo, and her colleagues found.

“The interaction in the present study between omega-6 PUFAs and HAs is not easily explained, and points toward the importance of examining the impact of food patterns rather than the influence of single dietary factors,” Sonestedt and her team state in the October 1 issue of the International Journal of Cancer.

HAs form in meat or fish cooked at high temperatures, and have been tied to breast cancer in rats. Rats fed a fatty diet having a high omega-6 content developed even more tumors in response to dietary HAs than rats given a low fat diet.

Sonestedt’s team examined whether HA consumption was related to breast cancer, and whether omega-6 PUFA intake played a role in this relationship, in women enrolled in the Malmo Diet and Cancer study.

The cohort included 11,699 women 50 and older. During follow-up, which averaged about 10 years, 430 of the women were diagnosed with breast cancer.

Women who consumed the most HAs were at no greater breast cancer risk than those who consumed the least, the researchers found. However, in women with low HA consumption, high omega-6 PUFA intake increased the likelihood of being diagnosed with breast cancer.

A previous analysis of data from this study had found high blood fats and high insulin levels -- both of which have been linked to breast cancer -- in women who consumed lots of low-fiber bread, Sonestedt and her team note. This could help explain the relationship in the current study, because women with low HA consumption ate more bread, cookies and cakes, the researchers say.

They conclude, based on their research, that a diet “very high in omega-6 PUFA may promote breast cancer development.”

SOURCE: International Journal of Cancer, October 1, 2008.