Omega-3s and Omega-6s May Reduce Overall Cancer Risk, Study Finds

Fish oil supplements may help lower the overall risk of developing cancer, according to a recent study published in the International Journal of Cancer.

Researchers in the United Kingdom analyzed data from over 250,000 people who took blood tests to measure levels of omega-3 and omega-6 fatty acids. The participants were then monitored for a little more than a decade.

Higher levels of omega-3 and omega-6 were associated with reduced overall risk of cancer. While the individual risk reduction seems modest, small improvements across large populations could translate to significant health benefits.

People who had higher levels of omega-3s had lower rates of colon, stomach, and lung cancer, in addition to lower rates of other digestive tract cancers, when followed up after a decade, according to Yuchen Zhang, lead author of the study and a doctoral student in the College of Public Health at the University of Georgia.

High omega-6 levels led to lower rates of 14 different cancers, including brain, malignant melanoma, and bladder.

In the study, the benefits of high levels of fatty acids were independent of risk factors like body mass index (BMI), alcohol use, and physical activity.

But some experts say more research is still needed, especially since the study found a slight increase in prostate cancer among men who had higher levels of omega-6.

“This is an interesting study with promising findings,” Marissa Shams-White, PhD, MPH, senior principal scientist for population science at the American Cancer Society, told Verywell. “The study had many strengths, including that it was in a very large population. However, this is only one study, and findings may not be generalizable to all adults.”

Omega-3 and omega-6 fatty acids are important sources of dietary fats. While omega-3s can promote heart and brain health and reduce inflammation, omega-6s can provide energy and support cellular health.

Shams-White explained that observational studies such as this one examine associations between nutrients and health outcomes, but they cannot establish causation that proves fatty acid intake changes cancer risk.

“There is currently inconsistent evidence that fish oil supplements, and any other dietary supplements, may affect cancer risk,” Shams-White said. “Taking supplements may impact health differently than consuming nutrients through foods in your diet.”

The current cancer prevention guidelines recommend consuming nutrients through diet but not taking dietary supplements for cancer prevention, she added.

“Dietary sources are rich in other nutrients and vitamins that may interact to together impact health. As an example, fish are not only great sources of omega-3s, but they can also be good sources of protein, vitamin D, and B vitamins like selenium and potassium,” Shams-White said.

Research suggests that most Americans consume about 10 times more omega-6s than omega-3s, according to Amy Bragagnini, MS, RD, a spokesperson for the Academy of Nutrition and Dietetics and clinical oncology dietitian at Trinity Health Lacks Cancer Center in Grand Rapids, Michigan.

Foods that are rich in omega-3s include fatty fish like salmon and sardines, chia seeds, flax seeds, walnuts, and spinach. Omega-6 fats mainly come from vegetable oils like sunflower oil and safflower oil.

“I would encourage people to aim to get more omega-3 fatty acids from food when they can,” Bragagnini told Verywell, adding that it’s best to increase omega-3 intake instead of reducing omega-6s in your diet.

Adults should aim to consume a total of 8 ounces of fish per week, according to the U.S. dietary guidelines.

Bragagnini noted that if her patients struggle to add omega-3s to their diet, then she’d advise them to consult a doctor about taking a supplement.