A new study using neuroimaging and cognitive testing found significantly less brain atrophy and better scores on cognitive tests among older individuals taking fish-oil supplements than among those not taking supplements. These beneficial effects were seen only in those with normal cognitive abilities at the beginning of the study, however. No improvement was seen in participants who already displayed mild cognitive impairments or Alzheimers.
Lead researcher Laurie A. Daiello, PharmD, of Brown University, cautioned, Retrospective studies cannot establish cause and effect, so we cant make a global recommendation that everyone should start taking fish-oil supplements. But the findings highlight the need for additional research on the effects of long-term fish-oil use on brain health in later life.
The findings, published in the journal Alzheimers & Dementia, add to a growing body of evidence that supplements of the omega-3 fatty acids found in fish (DHA and EPA) can benefit the brain and cognitive behavior. According to Robin B. Kanarek, PhD, Tufts professor of psychology,
Previous randomized controlled trials assessing the influence of omega-3 supplementation on cognitive function in healthy older adults suggest that DHA (800-900 milligrams per day) can improve verbal, visuospatial and episodic memory, and that higher serum and plasma DHA are generally associated with improved cognitive scores on these measures.
LOOKING BACKWARD: In the new study, Daiello and colleagues took a retrospective look at the effects of fish-oil supplements on brain activity and behavior in 819 older adults who participated in the Alzheimers Disease Neuroimaging Initiative. Every six months, participants completed standard cognitive tests for memory and other mental abilities and underwent brain magnetic resonance imaging (MRI) scans. Daiello and colleagues correlated the results on the scans and cognitive measures with participants use of fish-oil supplements during the four-year study period: Did those who took fish-oil pills fare better?
The study group included 229 older adults without cognitive deficits when the study began, 397 who were diagnosed with mild cognitive impairments, and 193 with Alzheimers disease. Only those in the initially normal group displayed an association between fish-oil supplementation and cognitive protection. But that apparent benefit was significant-less brain atrophy in key neurological areas as well as better test scores. Individuals with the most-studied genetic risk factor for Alzheimers disease, APOE-4, did not seem to benefit from fish-oil pills, nor did those already diagnosed with the disease or with mild cognitive impairments.
HOW MUCH AND WHO?: The study also did not address the dosage of fish oil that participants took, and prior research suggests that might be important. Tufts Kanarek points out that in another study, a lower dose of DHA (such as about 250 milligrams a day) did not influence cognitive function.
As for people already suffering cognitive decline or dementia, the evidence for the benefits of fish oil is mixed. Some findings suggest that supplementation with omega-3s may improve cognitive functions in individuals with mild cognitive deficits or Alzheimers disease, Kanarek says.
For example, she notes that in some studies, omega-3s reduced decrements in memory and attention in older adults with mild Alzheimers disease and reduced memory impairments in individuals with more severe Alzheimers disease. Similarly, omega-3 supplementation improved global clinical status in individuals with mild to moderate Alzheimers disease. DHA-rich fish oil enhanced verbal fluency in older adults with mild cognitive impairment, and both EPA- and DHA-rich fish oil improved depressive symptoms.
In contrast, however, other work showed no influence of omega-3 supplementation in individuals with mild to moderate Alzheimers disease-as did this latest study.
BRAIN FOOD: It makes sense that fish-oil supplements might benefit the brain. Lipids, a collective term for fats and oils, make up about 50%-60% of the brains dry weight, and the omega-3 fatty acid DHA (docohexaenoic acid) is the most abundant fatty acid found in nerve cell membranes. The DHA composition of the brain decreases with age as a result of the cumulative effects of oxidative damage, so getting extra DHA might make up for that loss.
To date, however, even with this new study, the evidence of benefit is not as strong for obtaining fish oil in pill form as it is for consuming omega-3s from dietary sources such as fish.
Your Brain on Fish
One important study of the brain benefits of eating fish was conducted by Tufts HNRCA Lipid Metabolism Laboratory in 2006. Participants with the highest blood levels of the omega-3 DHA reported that they ate an average of nearly three fish servings a week. Those with higher blood levels of DHA, as well as those eating the most fish, had a dramatically lower risk of dementia and Alzheimers disease on followup. Subjects with the highest DHA levels had a 47% reduced risk of dementia and a 39% lower risk of Alzheimers.