The omega-3 fatty acids found in foods like fish and fish oil supplements (primarily EPA and DHA) have been under scrutiny lately. For example, a recent story in the Washington Post questioned the value of taking fish oil for preventing heart disease. Now, a new study published in the journal JAMA has found that supplementing with 1,000 mg of combined EPA and DHA per day for five years had no effect on cognitive function in older adults with age-related macular degeneration.
Interestingly, the new study’s findings seem to conflict with some previous research. For instance, a 2013 clinical trial with 36 participants, published in the journal Psychopharmacology, found that taking fish oil supplements (providing 1,740 mg of combined EPA and DHA per day) was linked to improved cognitive function in Malaysian adults with low socioeconomic status that were already experiencing mild cognitive impairment.
Here are some possible explanations for these contradictory findings:
- Nutritional differences. The participants in the 2013 study had low dietary fish intake due to financial constraints, while the participants in the current study were not specifically of low socioeconomic status or known to have low dietary fish intake. It’s possible that people with low fish intake could have fatty acid deficiencies and may be more likely to benefit from supplementation. In addition, the supplements used in the 2013 study provided more EPA and DHA than those in the new study. The 2013 study also used whole fish oil, which provides appreciable amounts of other fatty acids, as well as vitamins A and D.
- Health differences. The new trial included people with age-related macular degeneration, while the 2013 trial included people with mild cognitive impairment. People with these conditions are likely to have different needs from one another, and may respond to supplements differently.
- Timing. The authors of the more recent study speculated that their treatment protocol may have been "too little, too late," suggesting that it may be important to start taking omega-3s earlier in life.
The take-away is that more research is needed to understand the relationship between omega-3 supplementation and cognitive function in different groups of people. In addition, the potential health benefits of omega-3s should not be discounted. Previous research has associated omega-3s with increased bone health and immune system support, and decreased incidence of depression.