According to a recent research, consumption of fatty fish like salmon and sardines rich in omega-3 fatty acids may help in protection against kidney cancer.
A big, 15-year study was conducted in Sweden on women focusing on their consumption of fatty and lean fish and its effect on kidney cancer risk. It concluded that those who ate great amounts of fatty fish, i.e., more than one serving in a week, had 44% lower risk for the most common type of kidney cancer; renal cell carcinoma than those who did not consume any fish.
"That's substantial," said Eugenia Calle, director of analytic epidemiology for the American Cancer Society. "There is very little published on this topic -- it may be the only study to look at fatty fish and kidney cancer."
The study was published in the Sept. 20 issue of the Journal of the American Medical Association.
"Previous studies on fish consumption and cancer risk produced inconsistent results, and they were limited in that they looked at all types of fish consumption, " Calle said.
"There has been some experimental data with animals and cells that suggest fatty fish, with their abundance of omega-3 fatty acids and Vitamin D, may protect against cancer, " she added.
"The Swedish study, led by Alicja Wolk of the Karolinska Institutet in Stockholm, is probably the first study to look at fatty fish consumption. There's a lot of hypotheses but not a lot of studies yet," Calle said.
The study was conducted on 61,433 women. The consumption of fatty fish like salmon, herring, sardines, and mackerel; lean fish like cod, tuna and fresh water fish; and seafood like shrimp, lobster and crayfish was observed. A food frequency questionnaire was given to the participants when the study began in 1987 and again in September 1997.
150 kidney-cancer cases were reported in the 15-year follow-up (1987-2004). Lower incidence of kidney cancer was reported among women who consumed fatty fish once a week or more. However, no link was found with the consumption of lean fish or other seafood.
"In this large population-based cohort with data on long-term diet, we found that women who consumed one or more servings of fatty fish per week had a statistically significant 44 percent decreased risk of RCC (renal cell carcinoma) compared with women who did not consume any fish. Women who reported consistent long-term consumption of fatty fish at baseline and 10 years later had a statistically significant 74 percent lower risk," the authors wrote in a prepared statement.
"Our results support the hypothesis that frequent consumption of fatty fish may lower the risk of renal cell cancer possibly due to increased intake of fish oil rich in eicosapentaenoic acid and docosahexaeneoic acid as well as vitamin D. Our results, however, require confirmation because this is the first epidemiological study addressing this issue," say the researchers.
According to them, there were huge differences in the omega-3 fatty acids and vitamin D contents between fatty fish and lean fish. 20-30 times higher amounts of marine omega-3 polyunsaturated fatty acids was found in fatty cold-water fish than in lean fish and the vitamin D content was 3-5 times higher in the former than the latter. The occurrence and progression of renal cell carcinoma has been associated with lower levels of serum vitamin D.
However, the findings of this study contradicts a major review published earlier this year according to which omega-3 fatty acids derived from fish or fish-oil supplements did not prevent cancer. This review of over 38 studies found no proof that fish-rich diet fights any type of cancer.
"These conflicting data showed omega-3 fatty acids definitely have health benefits, but they are not a panacea. Preventing cancer is not one of the things omega-3 fatty acids do," said lead researcher Dr. Catherine MacLean, a natural scientist at Rand Health and a rheumatologist at the Greater Los Angeles VA Healthcare System.
The study featured in the Jan. 25 issue of Journal of the American Medical Association.
"Kidney cancer isn't that common in the United States, ranking No. 7 for men and not making the top 10 cancers for women. So the public health impact is not as great as it would be, say, for breast, lung, prostate," Calle said. "But, in terms of general interest, if [fatty fish] were associated with a decreased risk of additional cancers, that would be a very important message," she added.
"You can't go wrong eating fish," Calle said, "the American Cancer Society does not have specific recommendations on the type of fish to eat. As more data become available, our dietary recommendations are reviewed and updated."