As a dietitian, I am concerned about supplementing with fish oil for breast cancer prevention and want to offer a different perspective on the fish oil hype [Fish Oil May Reduce Cancer Risk, 7/12/10].

First, scientific studies have found major health risks associated with fish oil intake. Researchers have found high levels of contaminants such as organochlorine pesticides, methyl mercury, and polychlorinated biphenyls (PCBs), even in molecularly distilled fish oil. And the omega-3s in fish oils are actually highly unstable molecules that tend to decompose and unleash dangerous free radicals. Furthermore, the global supply of fish is in danger and the distribution of fish oil does not promote ecologically sustainable practices.

Fish consumption has actually been tied to breast cancer. A study from Nutrition and Cancer shows that postmenopausal women who consume a mere 25 grams of fish per day (just under 1 oz) have a 14 percent greater risk of developing estrogen-positive breast cancer.

Fish and fish oil intake have also been tied to increased diabetes risk. In a recent Harvard study, researchers followed 195,204 adults for 14 to 18 years and found that those who consumed more fish or fish oil had a higher risk of developing diabetes. The risk increase was modest for occasional fish eaters, but rose to a 22 percent increased risk for women consuming five or more fish servings per week.

Microalgae-based DHA supplements provide the benefits of omega-3s without any harmful contaminants or potential allergens. If health-conscious adults want to supplement omega-3, plant sources are a safer option & can work as efficiently as fish oil. However, it may not be necessary according to health professionals.

Professor Frank Sacks with the Harvard School of Public Health reports that with adequate intake of plant omega-3s, essential fatty acid supplementation is likely unnecessary. According to Sacks and other nutrition experts from the World Health Organization, it is likely fine to rely on plant sources of omega-3 for the conversion of long-chain omega-3s (EPA/DHA).

If our diets weren’t so high in fat, we would not need to supplement omega-3s. As people consume more fatty meat and other animal products, their total fat intake increases dramatically, especially in the form of omega-6, and the body cannot efficiently process the essential fats that occur naturally in healthful plant foods like walnuts, flax seed, dark green leafy vegetables, and soybeans. When the ratio of essential fatty acids is geared toward omega-6, metabolism of both fats becomes altered.

High-fat diets are a major risk factor for heart disease, diabetes, and some cancers, including breast cancer. If we would address this underlying risk factor and lower our total fat intake, we would have no reason to supplement essential fatty acids—and we would have much lower rates of cancer and other chronic diseases.

A low-fat diet rich in fruits, vegetables, nuts, seeds, and legumes can provide all the essential fatty acids we need—and it helps fight heart disease, obesity, type 2 diabetes, and some cancers.

Joseph Gonzales, R.D., is a dietician for The Cancer Project in Washington D.C.  He holds a Bachelor of Science in Nutrition from Bastyr University.