STOCKHOLM, SWEDEN. It is estimated that in the U.S. about 40,000 individuals will be diagnosed with kidney cancer in 2006 and about 13,000 will die from the disease. A recent study from Sweden provides evidence for a simple risk reduction strategy—eat fatty fish. This study was initiated in the late 1980s and involved 90,000 Swedish women who were questioned about their dietary habits and then followed for more than a decade. Women who consumed at least one portion of fatty fish (rich in omega-3 fatty acids) each week during the study period ending in 2004 had a reduced risk of kidney cancer of 74% when compared to those who ate no fatty fish. However, eating lean non-fatty fish produced no protection. This result is based on a subgroup of 36,664 women who provided fish consumption information at baseline and again in 1997. There were 40 incident kidney cancer cases during the 1998-2004 follow-up. In this study, omega-3-rich fatty fish included salmon, raw (pickled) herring, sardines and mackerel. Non-fatty fish included cod, tuna, fresh-water fish, shrimp and lobster.
The authors comment that these results support the hypothesis that the lower risk of kidney cancer is possibly due to the increased intake of fish oil rich in the two marine omega-3 polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) as well as vitamin D. They discuss the evidence for the biological plausibility of this hypothesis. The authors also point out that an explanation for the null results from earlier studies of the influence of fish consumption on cancer may have been the failure to distinguish fatty from not-fatty fish intake. As regards vitamin D, they discuss studies that found a connection between kidney cancer and vitamin D deficiency as measured by serum marker levels. This epidemiologic study, according to the authors, is the first to address this dietary association.
Wolk, A et al. Long-term Fatty fish Consumption and Renal Cell Carcinoma Incidence in Women. Journal of the American Medical Association, 2006, Vol. 296, No. 11, pp. 1371-6