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.

--Ralph W. Moss, Ph.D.

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.

The Moss Reports is on Facebook (Get Connected)