Fish Oil And Cancer - New Findings

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. 

TO BE COMPLETED, WITH REFERENCES, NEXT WEEK.

--Ralph W. Moss, Ph.D.