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updated: 5/28/2012 6:42 AM

Fish oil may reduce weight loss during chemotherapy

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Last week, I gave a lecture for the American Lung Association and the topic was alternative therapies for treating lung cancer.

In preparing for the lecture, I explored the research on the use of fish oils to minimize the loss of muscle mass during chemotherapy. Although there are a number of studies suggesting that it can prevent the weight loss often associated with chemotherapy, most studies do not show a definitive benefit. However, one recent study did find a strong, positive relationship with fish oil and the prevention of weight loss in lung cancer patients undergoing chemotherapy.

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Fish oil contains two important omega-3 oils, docosahexaenoic acid and eicosapentanic acid. DHA is an important fat because it comprises 40 percent of all the polyunsaturated fatty acids in the brain and, by weight, is 50 percent of nerve membrane. EPA is essential because it is a precursor molecule for many anti-inflammatory compounds as well as a precursor for DHA. Humans cannot synthesize either EPA or DHA very efficiently and these oils must be obtained through diet -- either eating fish or taking fish oil supplements.

Weight loss is a common side effect of chemotherapy in patients with progressive cancer. This weight loss can negatively impact the patient's ability to continue with chemotherapy and may decrease survival. In a number of studies, incorporating fish oil containing DHA and EPA into the diet have suggested an increase in survival probably through reduced weight loss and protein wasting. However, three large clinical trials failed to demonstrate a clear benefit of fish oil preserving body weight in cancer patients. Confounding factors in these studies included uncertain compliance and that fish oil supplementation was started late in therapy, after the patients were already debilitated.

One recent study published in the medical journal Cancer introduced EPA at the beginning of chemotherapy. In this study, 104 participants either took EPA or a placebo before starting chemotherapy. Chemotherapy and the study lasted about 10 weeks. The authors also followed weight, muscle mass and blood levels of omega-3 fats to see if higher blood levels correlated with better muscle preservation. This is something that the other studies had not done. What they found was that those participants who took fish oil did not lose as much muscle as those participants not taking fish oil. Indeed, there was a strong, inverse relationship between the amount of omega-3 fats in the blood and muscle wasting. Essentially, more fish oil meant less weight loss.

There are few side effects to fish oil supplementation, mostly related to the stomach. There is some concern about fish oil supplements containing mercury and pesticides. Good fish oils undergo a purification process called molecular distillation, essentially removing contaminants. These manufacturers will label their fish oil as "molecularly distilled." There is also some concern about fish oil and an increased risk of bleeding. This may not be a real concern unless taking more than 5,000 milligrams of fish oil per day.

• Patrick B. Massey, M.D., Ph.D is medical director for complementary and alternative medicine for the Alexian Brothers Hospital Network. His website is

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