Western Herbal Medicine and Nutrition by Gabriel MacSharry

Omega 3 fish oils and cancer

Healthy Omega 3

Interesting new findings regarding Omega 3 fish oils and cancer treatment and prevention, see inside for more

Fish Oil And Cancer - New Findings

By Ralph W. Moss, Ph.D.

Swedish scientists recently published an important paper on the positive impact of omega-3 fatty acids (which are found mainly in fish oil) on a certain type of childhood cancer called neuroblastoma (Gleissman 2010). These Karolinska Institute scientists had previously shown that DHA (the most unsaturated form of fatty acid in fish oil) could cause apoptosis (i.e., programmed cell death) in cancer cells. They have now extended their work to experimental animals, showing that fish oil supplementation caused either stabilization or actual regression of tumors in these animals. As they state, DHA "is a promising new agent for cancer treatment and prevention of minimal residual disease" (ibid). Their conclusions, as I shall show, also have relevance to a broader range of adult cancers.

The paper actually encompasses two parts, one on treatment, the other on prevention. In the prevention half, they gave DHA as a food supplement to rats before the animals were implanted with human neuroblastoma cells. (Because they lack a thymus, the rats in question are unable to reject tissue from a foreign species.) In the treatment half of the study, athymic rats that already had established neuroblastomas were force fed DHA daily and their tumor growth and DHA levels were then monitored. The authors concluded that "untreated control animals developed progressive disease, whereas treatment with DHA resulted in stable disease or partial response." The response depending on the dose of DHA.

Neuroblastoma is a tumor of the sympathetic nervous system that occurs in children. In fact, it accounts for 6 to 9 percent of all childhood cancers. It is the most deadly solid tumor of childhood outside the brain. "Despite intensive treatment modalities, the cure rate for these patients is less than 50 percent," the authors report, "and the majority experience relapse from minimal residual disease." Needless to say, there is an urgent need for new treatment ideas.

There appears to be a very special relationship between DHA and nerve tissue. For instance, a deficiency of DHA will lead to delayed neural development. Compared to normal nerve tissue, neuroblastoma is "profoundly deficient in DHA," whereas the level of the competing omega-6 fatty acid arachidonic acid (AA) is increased. This suggested to the authors that "an imbalance between omega-3 and omega-6 fatty acids may serve as an adaptation mechanism in nervous system tumors." Logically, then, one might expect the addition of DHA to slow or even stop the growth of neuroblastoma.

This is indeed what happened when they gave DHA supplements. The authors reported: "In the DHA-supplemented group the mean time to tumor take was significantly delayed compared to the control group" (ibid.). One rat receiving the DHA-enriched diet did not develop tumors at all. In the treatment part of the study, the median tumor volume index at the end of the experiment (day 12) was 3.72 for animals receiving one gram of DHA per kilogram of body weight, 5.47 for animals receiving half a gram per kilogram of DHA, and 9.48 in the control animals. The results were statistically significant. Put another way, a high dose of DHA decreased normal tumor growth by about two-thirds. As was predicted in the authors’ ‘omega-3 deficiency’ theory, the level of DHA in the tumor tissue tripled in the higher-dose treatment group vs. the controls.

The finding that DHA supplements cut the amount of tumor formation by two-thirds in experimental rats was astonishing, but not exactly new. It was in line with previous findings that a fish oil-enriched diet could inhibit the formation of various other kinds of tumors, including papillomas (Akihisa 2004), breast cancer (Manna 2008, Yuri 2003, Noguchi 1997), cancers of the large and small intestines (Toriyama-Baba 2001) lungs (Toriyama-Baba 2001), colon cancer (Takahashi 1993, Iigo 1997), sarcoma (Ramos 2004), and prostate cancer (Kelavkar 2006). Other studies have shown that omega-3 is strongly associated with a decreased risk of aggressiveness in prostate (Fradet 2006), kidney (Wolk 2006) and breast cancer (Kim 2009).

But DHA supplementation worked better at preventing the occurrence or recurrence of tumors than at treating established tumors. "Our study shows that DHA given as a daily oral supplement displays a moderate capacity to reduce neuroblastoma growth in the majority of treated animals," Judith Gleissman and her Karolinska coworkers wrote, "but not in all." Some animals simply did not incorporate DHA into their tumor tissue, and it was precisely those animals that did not respond to the treatment.

Do these recent Swedish findings have relevance to cancers in humans, including, but not limited to, children with neuroblastoma? I believe they do. The authors point to a study in an Inuit population of Alaska, which has a DHA intake several-fold higher than typical Caucasians. In one study, this group’s neuroblastoma rate was one-tenth that of a comparable lower-48 American population (Dewailly 2001). Alarmingly, in most of America, the ratio of omega-3 to omega-6 fatty acids has "dropped precipitously" over the past few decades. This bodes ill for American children and their parents and loved ones.

Eating more fatty fish seems, even more than ever, a prudent thing to do. Children, too, should be encouraged to increase their DHA intake through fatty fish consumption. However, with the Gulf of Mexico oil spill, finding good sources of non-contaminated fish is likely to become even more difficult than it already has been. High quality supplements of DHA and EPA may thereore be the best solution for most readers. For vegetarians, getting sufficient amounts of DHA and EPA can be a challenge. The best sources are walnuts, flaxseeds and flaxseed oil, olive oil, canola (rapeseed) oil, and avocado. DHA supplements derived from microalgae, not fish, are also readily available. There are also three or four clinical trials underway to test the effect of DHA and other omega-3 fatty acids in various kinds of cancer, such as lung, breast and lymphoma. Readers can find out about these by entering the terms "DHA," "EPA" and cancer into the Clinicaltrials.gov database.

References:

Dewailly E, Blanchet C, Lemieux S, Sauve L, Gingras S, Ayotte P, Holub BJ. n-3 Fatty acids and cardiovascular disease risk factors among the Inuit of Nunavik. Am J Clin Nutr 2001;74:464-73.

Fradet V, Cheng I, Casey G, Witte JS. Dietary Omega-3 Fatty Acids, Cyclooxygenase-2 Genetic Variation, and Aggressive Prostate Cancer Risk. Clin Cancer Res 2009.

Gleissman H, Segerström L, Hamberg M, Ponthan F, Lindskog M, Johnsen JI, Kogner P. Omega-3 fatty acid supplementation delays the progression of neuroblastoma in vivo. Int J Cancer. 2010 May 24. [Epub ahead of print]

Iigo M, Nakagawa T, Ishikawa C, Iwahori Y, Asamoto M, Yazawa K, Araki E, Tsuda H. Inhibitory effects of docosahexaenoic acid on colon carcinoma 26 metastasis to the lung. Br J Cancer 1997;75:650-5.

Kelavkar UP, Hutzley J, Dhir R, Kim P, Allen KG, McHugh K. Prostate tumor growth and recurrence can be modulated by the omega-6:omega-3 ratio in diet: athymic mouse xenograft model simulating radical prostatectomy. Neoplasia 2006;8:112-24.

Kim J, Lim SY, Shin A, Sung MK, Ro J, Kang HS, Lee KS, Kim SW, Lee ES. Fatty fish and fish omega-3 fatty acid intakes decrease the breast cancer risk: a case-control study. BMC Cancer 2009;9:216.

Manna S, Chakraborty T, Ghosh B, Chatterjee M, Panda A, Srivastava S, Rana A. Dietary fish oil associated with increased apoptosis and modulated expression of Bax and Bcl-2 during 7,12-dimethylbenz(alpha)anthracene-induced mammary carcinogenesis in rats. Prostaglandins Leukot Essent Fatty Acids 2008;79:5-14.

Noguchi M, Minami M, Yagasaki R, Kinoshita K, Earashi M, Kitagawa H, Taniya T, Miyazaki I. Chemoprevention of DMBA-induced mammary carcinogenesis in rats by lowdose EPA and DHA. Br J Cancer 1997;75:348-53.

Ramos EJ, Middleton FA, Laviano A, Sato T, Romanova I, Das UN, Chen C, Qi Y, Meguid MM. Effects of omega-3 fatty acid supplementation on tumor-bearing rats. J Am Coll Surg 2004;199:716-23.

Takahashi M, Minamoto T, Yamashita N, Yazawa K, Sugimura T, Esumi H. Reduction in formation and growth of 1,2-dimethylhydrazine-induced aberrant crypt foci in rat colon by docosahexaenoic acid. Cancer Res 1993;53:2786-9.

Toriyama-Baba H, Iigo M, Asamoto M, Iwahori Y, Park CB, Han BS, Takasuka N, Kakizoe T, Ishikawa C, Yazawa K, Araki E, Tsuda H. Organotropic chemopreventive effects of n-3 unsaturated fatty acids in a rat multi-organ carcinogenesis model. Jpn J Cancer Res 2001;92:1175-83.

Wolk A, Larsson SC, Johansson JE, Ekman P. Long-term fatty fish consumption and renal cell carcinoma incidence in women. JAMA 2006;296:1371-6.

Yuri T, Danbara N, Tsujita-Kyutoku M, Fukunaga K, Takada H, Inoue Y, Hada T, Tsuhttp://www.cancerdecisions.com/mambots/editors-xtd/mosimage.gifbura A. Dietary docosahexaenoic acid suppresses N-methyl-N-nitrosourea-induced mammary carcinogenesis in rats more effectively than eicosapentaenoic acid. Nutr Cancer 2003;45:211-7.

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