Can Fish Oil Supplements Reduce the Risk of Cancer?

To date, there have been inconsistent results when evaluating the association of essential fatty acid consumption and cancer incidence; however, new research published in the International Journal of Cancer provides some additional clarification.

The researchers used data from 250,000 people from the United Kingdom-based study and followed them for nearly 13 years. They found that participants who had higher levels of omega-3 fatty acids had lower risk of developing five different cancer types including colon, stomach, and lung. Individuals with high omega-6 fatty acid levels had a lower risk of developing 14 different cancers including brain, bladder, malignant melanoma, and others.

“Now that we have evidence that essential fatty acid consumption may play a preventive role versus cancer, it would be interesting to investigate whether their intake can improve cancer outcomes, to determine if diets rich in one or the other or both can improve survival of those already diagnosed,” said integrative health pioneer Ronald Hoffman, MD. “At any rate, the study is a repudiation of the notion that ultra low-fat diets are a panacea for cancer prevention.”

Dr. Hoffman also points out that the omega-6 finding is surprising.

“It is kind of paradoxical to see omega-6 consumption confer benefit because the majority of omega-6 consumed in the standard American diet is from ultra-refined seed oils,” points out Dr. Hoffman who is the host of the popular podcast Intelligent Medicine. “Perhaps the cancer-protective properties are a reflection of a more plant-based diet that features consumption of healthy omega-6 rich foods like nuts and seed.”

Another surprising aspect of this new study is that high omega-3 levels were associated with an increased risk of prostate cancer. Dr. Hoffman said there may be explanations for this association.

“Most men obtain their omega-3s from fish which can be contaminated with endocrine disruptors like polychlorinated biphenyls, which have been shown to increase the risk of prostate cancer,” explained Dr. Hoffman who also feels the omega-6:3 ratio is important. “This study confirms the oft-asserted deleterious effect of elevated omega-6:3 ratios which increases cancer rates because it is indicative of an overall poor diet,” said Dr. Hoffman.

Another issue Dr. Hoffman points out is the utilization of plasma testing. “It’s important to remember that essential fatty acid plasma levels are not a perfect proxy for consumption of foods rich in either,” he said. “Instead of being a reflection of consumption, they may be to some extent altered by metabolism which may be skewed in cancer-prone or cancer-resilient individuals.”

Clinical Conclusions

From a mechanistic standpoint, there is biological plausibility that omega-3s may help reduce the risk of cancer because of their anti-inflammatory, pro-apototic, and anti-proliferative effects.

While this latest study does not definitively confirm that taking a fish oil supplement will reduce the risk of all cancers, it does add to the conversation. Cancer type, gender, fatty acid source, and measurement all play a role. More research, especially regarding omega-6 fatty acids, needs to be conducted to further clarify the exact role essential fatty acids may play regarding cancer development and risk reduction.