FISH AND FISH OIL FOR PROSTATE CANCER PATIENTS,
By Charles “Snuffy” Myers, MD
information last updated on May, 2005
One of the healthiest low-fat proteins is fish. But fish and fish oil aren’t only a healthy option for loosing weight-they may help you control your prostate cancer because they’re high in DHA and EPA.
There are now more than 100 papers in the scientific literature that link arachidonic acid with prostate cancer. These papers suggest that arachidonic acid increases the aggressiveness of human prostate cancer because it is converted to a series of powerful hormones, including the prostaglandins, leukotrienes, and other eicosanoids. Studies show that drugs like aspirin and celebrex, which block the formation of some of these hormones, can either reduce the risk of prostate cancer or slow its progression. However, diet can also alter the amount of arachidonic acid in the body and its conversion to products that stimulate cancer growth.
Ocean fish body fat is rich in the omega-3 fatty acids DHA and EPA. These fatty acids block the conversion of arachidonic acid to these potentially damaging products and, as a result, have multiple health benefits. In fact, increasing dietary DHA and EPA may alleviate the symptoms of arthritis and other types of inflammation; it also decreases the tendency of platelets to trigger blood clots, and, in turn, reduces the risk of stroke. And over the past year, researchers showed that increasing your intake of DHA and EPA can dramatically reduce your risk of cardiac arrest because of abnormalities in heart contraction rhythm.
But some of fish oil’s health benefits appear to be unrelated to its ability to block the arachidonic acid metabolism. For example, DHA appears to play a critical role in the development and function of the human brain and retina. As a result, DHA supplements are routinely added to pediatric formulas used to replace human milk.
Since 1987, laboratory studies have repeatedly illustrated that DHA and EPA slow or arrest the growth of human prostate cancer cells. Researchers showed that this growth arrest is associated with decreased conversion of arachidonic acid to its potentially damaging metabolites. This past year, a very important clinical study published by the group at the Harvard School of Public Health examined the link between dietary fish consumption and the risk of metastatic prostate cancer (Augustsson, et al). This paper reported results from the Health Professionals Follow-up Study that involved 47,882 men over twelve years. During the twelve years, 2,483 cases of prostate cancer were identified. Of these, 617 were advanced and 278 were metastatic.
Eating fish more than three times a week reduced the risk of prostate cancer but had an even greater impact on the risk of metastatic prostate cancer. For each additional 500 mg of marine fat consumed, the risk of metastatic disease decreased by 24%! If this study were just an isolated report, one might be justified in ignoring the findings, but this paper is just the latest advancement in a long series of laboratory and clinical observations that document the favorable impact of ocean fish consumption on prostate cancer as well as general health.
Fish do not make DHA and EPA but obtain it from algae that form the bottom of the ocean food chain. In algae, these omega-3 fatty acids act to keep the membranes of the plants flexible and fluid at cold temperatures. Thus, fish that live in cold water are better sources of these omega-3 fatty acids than fish from tropical regions. Our oceans are also contaminated with mercury and other heavy metals, which tend to concentrate in fish at the top of the food chain. This is a problem with swordfish, many types of shark, and, to a lesser extent, tuna. Among large ocean fish, salmon shows less of a problem with mercury contamination. In general, small, fatty fish, such as herring and sardine, are the best compromise between high omega-3 fatty acid content and low mercury levels.
For vegetarians and vegans, DHA that has been extracted directly from algae and is marketed under the brand name Neuromins is available. The study by Augustsson, et al suggests that benefit increased as the dose of marine lipid increased. This makes it hard to give you a specific recommendation as to the optimum dose. For what it is worth, I take 2,000 mg of fish oil twice a day. Clinical trials in advanced cancer patients have administered doses as high as 6,000 mg a day without side effects.
The multiple health benefits attributed to DHA and EPA beg the question of why humans are so dependent on these fatty acids for optimal health. Scientists have approached this question within the context of human evolutionary history. Humans now live in a wide range of environments that range from the sea side to remote locations without any natural source of DHA; continued dependency on this fatty acid would seem to be disadvantageous. Most evolutionary explanations have revolved around variations of the Aquatic Ape Hypothesis, which focuses on the physical differences between humans and the other great apes.
The premise for this theory basically states that humans are uniquely suited for living at or near the ocean’s edge because of these physical differences. For instance, our bodies are relatively hairless, which allows us to swim with less resistance. Our longer legs make wading in water easier when compared to the anatomy of the large apes. Proponents of this theory point to other oddities (like the abundance of ear wax) that are an advantage in an aquatic environment. And human infants show an almost instinctive ability to swim, naturally holding their breath and exhibiting appropriate arm and leg motions.
More recently, advocates of the Aquatic Ape Hypothesis have noted that access to large amounts of DHA would be an advantage during pregnancy and early development that might have allowed a rapid evolutionary shift from the brain size of a large ape to that seen in man.
In other words, we are designed by nature to live on the shores of the ocean, eating fish and surfing! Unfortunately, hard evidence from the fossil record to support the Aquatic Ape Hypothesis is scant. Perhaps the most interesting set of observations is that most of the existing human remains that date from 100,000 or more years ago are found in caves along the South African coast and, more recently, in Eritrea, along the Red Sea coast.
Even if the Aquatic Ape Hypothesis is eventually disproved, laboratory and clinical evidence clearly document the importance of DHA and EPA for optimum human health. Now, the evidence strongly suggests that these fatty acids have an important role to play in suppressing the development and progression of prostate cancer.
References:
1. Verhaegen, M.J., The Aquatic Ape Theory: evidence and a possible scenario. Med Hypotheses, 16(1): 17-32, 1985.
2. Karmali, R.A., et al., The effects of dietary omega-3 fatty acids on the DU-145 transplantable human prostatic tumor. Anticancer Res, 7(6): 1173-9, 1987.
3. Chaudry, A.A., et al., Arachidonic acid metabolism in benign and malignant prostatic tissue in vitro: effects of fatty acids and cyclooxygenase inhibitors. Int J Cancer, 57(2): 176-80, 1994.
4. Langdon, J.H., Umbrella hypotheses and parsimony in human evolution: a critique of the Aquatic Ape Hypothesis. J Hum Evol, 33(4): 479-94, 1997.
5. Crawford, M.A., et al., Evidence for the unique function of docosahexaenoic acid during the evolution of the modern hominid brain. Lipids, 34 Suppl: S39-47, 1999.
6. Norrish, A.E., et al., Prostate cancer risk and consumption of fish oils: a dietary biomarker- based case-control study. Br J Cancer ,81(7): 1238-42, 1999.
7. Rose, D.P. and J.M. Connolly, Omega-3 fatty acids as cancer chemopreventive agents. Pharmacol Ther, 83(3): 217-44, 1999.
8. Lewis, N.M., S. Seburg, and N.L. Flanagan, Enriched eggs as a source of N-3 polyunsaturated fatty acids for humans. Poult Sci, 79(7): 971-4, 2000.
9. Walter, R.C., et al., Early human occupation of the Red Sea coast of Eritrea during the last interglacial. Nature, 405(6782): 65-9, 2000.
10. Aronson, W.J., et al., Modulation of omega-3/omega-6 polyunsaturated ratios with dietary fish oils in men with prostate cancer. Urology, 58(2): 283-8, 2001.
11. Chung, B.H., et al., Effects of docosahexaenoic acid and eicosapentaenoic acid on androgen- mediated cell growth and gene expression in LNCaP prostate cancer cells. Carcinogenesis, 22(8): p. 1201-6, 2001.
12. Hughes-Fulford, M., Y. Chen, and R.R. Tjandrawinata, Fatty acid regulates gene expression and growth of human prostate cancer PC-3 cells. Carcinogenesis, 22(5): 701-7, , 2001.
13. Inoue, K., H. Takano, and T. Yoshikawa, Fatty fish supplementation and risk of prostate cancer. Lancet, 358(9290): 1367, 2001.
14. Broadhurst, C.L., et al., Brain-specific lipids from marine, lacustrine, or terrestrial food resources: potential impact on early African Homo sapiens. Comp Biochem Physiol B Biochem Mol Biol, 131(4): 653-73, 2002.
15. Crawford, M.A., Cerebral evolution. Nutr Health, 16(1): 29-34, 2002.
16. Wahle, K.W. and S.D. Heys, Cell signal mechanisms, conjugated linoleic acids (CLAs) and anti-tumorigenesis. Prostaglandins Leukot Essent Fatty Acids, 67(2-3): 183-6, 2002.
7. Augustsson, K., et al., A prospective study of intake of fish and marine fatty acids and prostate cancer. Cancer Epidemiol Biomarkers Prev, 12(1): p. 64-7, 2003.
18. Giovannucci, E., et al., Nutritional Predictors of Insulin-like Growth Factor I and Their Relationships to Cancer in Men. Cancer Epidemiol Biomarkers Prev, 12(2): 84-9, 2003.
19. Terry, P.D., T.E. Rohan, and A. Wolk, Intakes of fish and marine fatty acids and the risks of cancers of the breast and prostate and of other hormone-related cancers: a review of the epidemiologic evidence. Am J Clin Nutr, 77(3): 532-43, 2003.
