Two of the most well-known beneficial effects of omega-3 fish oils are the improvements of cardiovascular and cognitive (heart and brain) health. These two benefits are usually investigated separately in studies, but a recent study published in the Nutrition Journal1 evaluated both together. They investigated the effects of fish oil supplementation on cognitive performance in healthy individuals, and related that outcome to cardio-metabolic risk factors. By doing so, they were able to make connections between heart health and cognitive health via the anti-inflammatory effects of fish oil.

Forty subjects were divided into two groups: the first received fish oil daily (3000 mg omega-3 including 1500 mg EPA + 1050 mg DHA) for five weeks followed by five weeks of placebo, and the second group received five weeks of placebo followed by five weeks of fish oil. (So each person acted as his own placebo, which helps reduce potential confounding factors.) The researchers found that daily fish oil supplementation significantly improved working memory, and there was a trend towards improvement in the ability to sustain attention. In addition, those subjects taking fish oil were also found to have decreased systolic blood pressure and triglycerides, both risk factors for the development of heart disease.

Stated the researchers, “The relation between higher levels of cardio-metabolic risk markers and inferior cognitive performance in healthy subjects, as observed in the present study, highlights the potential of a preventive dietary approach in the combat of both metabolic disorders and associated cognitive decline.”

They also found a reduction of inflammation (as measured by TNF-alpha concentrations) related to improved cognitive performance. They state, “The relationship between inflammation and cognitive performance indicate that omega-3 polyunsaturated fatty acids may be beneficial to cognitive functions due to a general anti-inflammatory effect, also involving effects on neuro-inflammation. Low grade chronic inflammation is increasingly also recognized as an important factor in the development of metabolic disorders such as diabetes type 2 and cardiovascular disease.”

That’s the premise underlying our latest book and PBS show, Heart of Perfect Health (now airing nationally)—silent inflammation is the common underlying factor that contributes to chronic disease, including heart health. And you know what? The gut is the main source of this silent inflammation. Heal your gut, heal your body.

The researchers made a smart choice when they decided to use a placebo that did not include another oil, like olive oil. Olive oil is a common placebo for fish oil, but since olive oil itself has some beneficial effects, including reduced inflammation, a positive benefit may be masked by the use of this oil. Instead, the researchers used a water-filled tablet to eliminate possible confounding factors. However, they did make one mistake—they measured plasma levels of omega-3 fatty acids instead of red blood cell membrane levels. Red blood cell membrane levels of omega-3 fats (also called the Omega-3 Index2) is the best marker of long-term omega-3 fatty acid intake and reflects tissue levels of omega-3s, which is where these fats are most utilized. They even mention, “An additional potential study limitation may be that no data is available concerning subjects’ blood- and/or red blood cell membrane phospholipid concentrations of omega-3 polyunsaturated fatty acids.” I have mentioned this as a potential limitation of the recent study that led to claims that fish oil supplementation does not lower heart disease risk.

Overall, it’s important to consider the totality of the evidence. And overwhelmingly, omega-3 fish oil supplementation has been associated with a wide array of benefits. This study is moving us one step closer towards understanding how the underlying disease process, in many different chronic illnesses, is the same. Rather than separating one disease from the other, by teasing out the underlying common causes, we have much greater potential to positively impact health.



  1. A. Nilsson, et al., “Effects of supplementation with n-3 polyunsaturated fatty acids on cognitive performance and cardiometabolic risk markers in healthy 51 to 72 years old subjects: a randomized controlled cross-over study.” Nutr J. 2012 Nov 22;11(1):99.
  2. W.S. Harris, “The omega-3 index as a risk factor for coronary heart disease.” Am J Clin Nutr. 2008 Jun;87(6):1997S-2002S.