Analysis of famed Physicians’ Health Study affirms prostate-protective potential of omega-3sby Craig Weatherby
Prostate cancer claims as many lives as breast cancer, albeit at more advanced ages.
Major risk factors for prostate cancer – including diets low in greens and high in red meat and dairy foods and (ironically) a longer lifespan – are rife in the developed world.
- Men who ate fish in abundance were 48 percent less likely to have died from prostate cancer over a 19-year period.
- Men who consumed the most omega-3s were 36 percent less likely to have died from prostate cancer.
- No preventive effect of fish or omega-3s was found, but this contradicts positive indications from a report that used blood tests to pinpoint actual omega-3 intake.
In 2005, prostate cancer affected 18 percent and killed three percent of of American men.
Evidence that omega-3 fatty acids curb the growth of cancer cells continues to mount.
In contrast, it is increasingly clear that – when consumed in excess – omega-6 fatty acids promote tumor growth.
Americans ingest omega-6 fats in enormous amounts, relative to intake of omega-3s.
This is because Americans eat little omega-3-rich seafood and scant amounts of omega-3-containig greens, while omega-6 fats abound in our most commonly consumed foods.
Omega-6 fats predominate in cheap vegetable oils – corn, soy, cottonseed, sunflower, safflower, and canola – in the packaged foods made with these oils, and in factory-farmed (grain-fed) fish, poultry, and meats.
In Japan – where omega-3 intakes (from seafood) are much higher and omega-6 intakes are much lower than in Western countries – death rates from prostate cancer are only about one-fifth to one-half of those found in the U.S. and Europe (Wakai K 2005).
The overlooked omega connection to prostate and other cancers
In March of 2006, we reported the results of two studies in human prostate cancer cells, which showed that omega-3s retard, and omega-6s fuel their growth (see “Omega-3s Slow, Omega-6s Speed Prostate Cancer Growth”).
Last August, scientists from UCLA reported similarly disturbing cell-study results (See “Prostate/Colon Risks Raised by High Omega-6/Omega-3 Ratio”).
And last fall, researchers at the Harvard School of Public Health reported that their analysis of data from the huge Physicians’ Health Study support the cancer-preventive potential of omega-3s and the risks of diets high in omega-6 fatty acids (See “‘Omega-Ratio’ Impact on Prostate Cancer Risk Affirmed”).
The results of a new analysis of data from the Physicians’ Health Study affirm the idea that people’s relative intakes of omega-3 and omega-6 fatty acids influence the risk or severity of major cancers.
Fatty fish may boost prostate cancer survival rates
The new study – also conducted by scientists from the Harvard School of Public Health – links increased intake of omega-3-rich seafood to a 48 percent rise in prostate cancer survival rates (Chavarro JE et al. 2008).
The researchers analyzed data collected from 20,167 men who participated in the Physicians’ Health Study.
The men selected were free of prostate cancer at the start of the study in 1983, and were followed for an average of 19 years.
During this nearly two-decade period, 2,161 men in the study were diagnosed with prostate cancer and 230 died from the disease.
The Harvard team compared the men’s reported diets to their health records.
These were their major findings:
- Men who ate fish five or more times a week were 48 percent less likely to have died from prostate cancer, compared with men who consumed fish less than once a week.
- Men who consumed the most omega-3s were 36 percent less likely to have died from prostate cancer, compared with men whose consumed the least omega-3s.
- Men’s fish intake appeared unrelated to the risk of developing prostate cancer.
Like all epidemiological studies, this latest analysis cannot prove that diets high in omega-3s curb the growth of prostate cancer.
But when considered in the light of other such studies – and substantial evidence from lab and animal research – its results suggest that fishy diets should be part of any prevention-oriented lifestyle plan.
Any such plan should also include exercise and diets high in fiber and colorful plant foods, and low in red meat.
Omega-3s’ apparent lack of preventive power appears misleading
In this new data analysis, men’s fish intake appeared unrelated to their risk of developing prostate cancer.
As the Harvard team concluded, “These results suggest that fish intake is unrelated to prostate cancer incidence but may improve prostate cancer survival.”
However, as we reported last year, the same Harvard team linked higher blood levels of fish-derived omega-3 fatty acids (DHA and EPA) to a 40 percent reduction in the risk of developing prostate cancer (See “‘Omega-Ratio’ Impact on Prostate Cancer Risk Affirmed”).
And as Vital Choice science advisor William E. Lands, Ph.D., always stresses, “the tissue is the issue” (An expert in fatty acid metabolism, Dr. Lands was a Professor of Biochemistry at the University of Michigan and the University of Illinois, and directed basic research at the National Institute on Alcohol Abuse and Alcoholism).
He means that blood tests provide far more reliable measures of people’s omega-3 intake, compared with the diet questionnaires used in most epidemiological investigation, including the Physicians’ Health Study that provided the data for the new analysis.
- Chavarro JE, Stampfer MJ, Hall MN, Sesso HD, Ma J. A 22-y prospective study of fish intake in relation to prostate cancer incidence and mortality. Am J Clin Nutr. 2008 Nov;88(5):1297-303.
- Chavarro JE, Stampfer MJ, Li H, Campos H, Kurth T, Ma J. A prospective study of polyunsaturated fatty acid levels in blood and prostate cancer risk. Cancer Epidemiol Biomarkers Prev. 2007 Jul;16(7):1364-70. Epub 2007 Jun 21.
- Collin SM, Martin RM, Metcalfe C, Gunnell D, Albertsen PC, Neal D, Hamdy F, Stephens P, Lane JA, Moore R, Donovan J. Prostate-cancer mortality in the USA and UK in 1975-2004: an ecological study. Lancet Oncol. 2008 May;9(5):445-52. Epub 2008 Apr 16.
- Gann PH, Hennekens CH, Sacks FM, Grodstein F, Giovannucci EL, Stampfer MJ. Prospective study of plasma fatty acids and risk of prostate cancer. J Natl Cancer Inst. 1994 Feb 16;86(4):281-6. Erratum in: J Natl Cancer Inst 1994 May 4;86(9):728.
- Hall MN, Campos H, Li H, Sesso HD, Stampfer MJ, Willett WC, Ma J. Blood levels of long-chain polyunsaturated fatty acids, aspirin, and the risk of colorectal cancer. Cancer Epidemiol Biomarkers Prev. 2007 Feb;16(2):314-21
- Harvei S, Bjerve KS, Tretli S, Jellum E, Robsahm TE, Vatten L. Prediagnostic level of fatty acids in serum phospholipids: omega-3 and omega-6 fatty acids and the risk of prostate cancer. Int J Cancer. 1997 May 16;71(4):545-51.
- Surveillance, Epidemiology and End Results (SEER) Program. Accessed online November 23, 2008 at http://seer.cancer.gov/statfacts/html/breast.html
- Surveillance, Epidemiology and End Results (SEER) Program. Accessed online November 23, 2008 at http://seer.cancer.gov/statfacts/html/prost.html
- Wakai K. [Descriptive epidemiology of prostate cancer in Japan and Western countries] Nippon Rinsho. 2005 Feb;63(2):207-12. Review. Japanese.