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Fatty Fish Seen Curbing Women’s Kidney Cancer Risks
9/25/2006
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Swedish study indicates that the omega-3s and vitamin D abundant in fatty fish help prevent kidney cancer in women
by Craig Weatherby 


We can hardly keep up with the stream of cell, animal, and human studies suggesting fish-rich diets may help reduce the risk of some of the most common and deadly cancers, including malignancies of the breast, colon, skin, liver, and blood.

 

Just last week, we reported research results indicating that consuming the US RDA for vitamin D (400 IU) slashes the risk of pancreatic cancer by a whopping 43 percent. Fatty fish are the richest food sources of vitamin D, with salmon leading the pack and sockeye ranking as the number one source.


Key Points

  • Women in large study who ate fatty fish weekly enjoyed a dramatic drop in their risk of kidney cancer.
  • Risk reduction linked to high levels of omega-3s and vitamin D in fatty fish (e.g., salmon and sardines).
  • Kidney cancer risk is raised by meats and smoking and cut by fruits and fish.

Now, findings from Sweden suggest that the high levels of vitamin D and long-chain “marine” omega-3s found in fatty fish can cut the risk of kidney cancer by a huge 74 percent margin.

 

Kidney cancer on the rise

The American Cancer Society estimates that 38,890 people will be diagnosed with kidney cancer in the United States this year, and that one in three (some 12,840 people) will die from the disease.

 

The new study (Wolk A et al 2006) looked at rates of renal (kidney) cell carcinoma or RCC, which accounts for 80 percent of all kidney cancers in the United States and has been on the rise over the past 30 years.

 

Prior research results indicate that smoking and diets high in fried or sautéed meats or poultry raise the risk of RCC, while diets rich in fruits and vegetables appear to reduce the risk, possibly because of their vitamin C content. Now it looks like fatty fish can join the list of preventive foods.

 

New findings flow from sizable Swedish study

The new results stem from the same Swedish Mammography Cohort study that confirmed the cancer-promoting effects of eating red meats (beef and pork) and the sausage, bacon, and cold cuts made from them (See “New Cancer Risk Findings”).

 

The Swedish Mammography Cohort study began when scientists at Sweden’s Karolinska Institute offered free mammography scans to 90,000 women in Uppsalaand Västmanland counties. The women ranged between 40 to 76 years of age, andSweden’s comprehensive patient registry showed that none had a previous cancer diagnosis.

 

Between March of 1987 and December of 1990, women who accepted the free mammography offer were mailed diet/lifestyle/health status questionnaires, and 61,443 completed and returned it.

 

The 56,030 participants who were still alive in the study area received a second questionnaire in September 1997. Of these women, 36,664 responded and met all the inclusion criteria. The Karolinska team analyzed the data from their responses, seeking any statistically significant associations between diet or lifestyle factors and cancer rates.

 

Results show fatty fish reduce kidney cancer risk

The Karolinska group compared the first and second questionnaires and scanned Sweden’s cancer patient registry to see whether the women in the study had been diagnosed with kidney cancer.

 

They concluded that the women who ate fatty fish regularly during the 15-year period enjoyed significant protection against renal (kidney) cancer:


  • The women who reported eating at least one portion of fatty fish a week had a 74 percent lower risk of renal (kidney) cancer, compared with those who never ate fatty fish.
  • The group who reported eating fresh fish at least once a week enjoyed a 44 percent reduction in risk.

Importantly, the results did not change when the researchers accounted for the cancer-promoting effects of various lifestyle and health factors.

 

In a press release, study co-author Alicja Wolk, DMSc made two key points:


  • “This is the first time that a link between the consumption of fatty fish and renal cancer has been studied.”
  • “The reason previous studies have been unable to demonstrate a link between fish consumption and renal cancer is that they made no distinction between fatty and non-fatty fish.”

Fatty fish protect, but lean species fail: Omega-3s and vitamin D called key

The Karolinska Institute team attributed the protective power of fatty fish to high levels of omega-3s and vitamin D: “Our results support the hypothesis that frequent consumption of fatty fish may lower the risk of RCC [kidney cancer] possibly due to increased intake of fish oil rich in [omega-3] eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA] as well as vitamin D.”

 

And, the Swedes noted that diets high in fatty fish raise blood levels of omega-3s: “Results from a cross-sectional study in 16 regions in Europe (the European Prospective Investigation into Cancer and Nutrition [EPIC]) showed greatly increased (3-4 fold) blood concentrations of [omega-3] eicosapentaenoic acid [EPA] in study participants from Sweden and Denmark who consumed fatty fish.” [Note: eating fatty fish also raises levels of omega-3 DHA, but the EPIC study authors did not measure it.]

 

As we’ve reported, the results of cell studies and recent epidemiological studies indicate that omega-3 fatty acids and vitamin D protect against cancer (To view past articles in “Vital Choices” go to our Newsletter archive and search for "cancer").

 

And, compared with lean species like cod or sole, fatty fish like salmon and sardines contain much higher levels of omega-3 fatty acids, and three to five times as much vitamin D.

 

(NOTE: Independent test results indicate that Pacific Albacore tuna is an exception to the general “more fat = more vitamin D” rule. While Pacific Albacore tuna is lower in omega-3s compared with salmon, sablefish, or sardines, only sockeye salmon contains more vitamin D: 1,170 IU per 6 oz serving of sockeye versus 925 IU per 6 oz serving of albacore.)

 

The fatty fish that the women in the Swedish study reported eating included salmon, herring, sardines and mackerel, while the non-fatty species included cod and tuna.

 

The results of this large, scientifically sound study suggest that in addition to cardiovascular benefits, eating salmon, sardines, and other fatty fish once a week offers a good way to avoid cancer of the kidneys.

 

 

Sources

  • Boeing H, Schlehofer B, Wahrendorf J. Diet, obesity and risk for renal cell carcinoma: results from a case control-study in Germany. Z Ernahrungswiss. 1997 Mar;36(1):3-11.
  • Chow WH, Gridley G, McLaughlin JK, Mandel JS, Wacholder S, Blot WJ, Niwa S, Fraumeni JF Jr. Protein intake and risk of renal cell cancer. J Natl Cancer Inst. 1994 Aug 3;86(15):1131-9.
  • Fujioka T, Suzuki Y, Okamoto T, Mastushita N, Hasegawa M, Omori S. Prevention of renal cell carcinoma by active vitamin D3. World J Surg. 2000;24:1205-1210.
  • Larsson SC, Kumlin M, Ingelman-Sundberg M, Wolk A. Dietary long-chain n-3 fatty acids for the prevention of cancer: a review of potential mechanisms. Am J Clin Nutr. 2004;79:935-945.
  • Larsson SC, Orsini N, Wolk A. Processed meat consumption and stomach cancer risk: a meta-analysis. J Natl Cancer Inst. 2006 Aug 2;98(15):1078-87. 
  • Lindblad P, Wolk A, Bergstrom R, Adami HO. Diet and risk of renal cell cancer: a population-based case-control study. Cancer Epidemiol Biomarkers Prev. 1997 Apr;6(4):215-23.
  • McCabe AJ, Wallace JM, Gilmore WS, McGlynn H, Strain SJ. Docosahexaenoic acid reduces in vitro invasion of renal cell carcinoma by elevated levels of tissue inhibitor of metalloproteinase-1. J Nutr Biochem. 2005;16:17-22.
  • McLaughlin JK, Gao YT, Gao RN, Zheng W, Ji BT, Blot WJ, Fraumeni JF Jr. Risk factors for renal-cell cancer in Shanghai, China. Int J Cancer. 1992 Oct 21;52(4):562-5.
  • Wolk A, Larsson SC, Johansson JE, Ekman P. Long-term fatty fish consumption and renal cell carcinoma incidence in women. JAMA. 2006 Sep 20;296(11):1371-6.

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