Taking omega-3 fatty acids doesn't help brain function in healthy older adults, at least in the short term, according to a new review that adds to the debate over fish oil and people's health.
The researchers looked at the results of three randomized controlled trials involving a total of 3,500 healthy adults over age 60, a portion of whom were given omega-3 fatty acid supplements. During the studies, which lasted from six to 40 months, the participants taking omega-3s demonstrated no advantage over the control groups in tests measuring memory, verbal fluency or symptoms of dementia.
Observational studies have suggested consuming fish oil benefits the brain, and some researchers have proposed a plausible mechanism to explain such benefits, but "when you look at the papers, there's no evidence for taking these supplements" in the short term, said study author Alan Dangour, a senior lecturer in public health nutrition at the London School of Hygiene and Tropical Medicine.
In two of the three studies, participants took either omega-3-enriched gel capsules, or capsules containing sunflower or olive oil. In the other study, participants received tubs of margarine to use as they wished; only some of the tubs were enriched with omega-3s.
On tests of cognitive function — one test, for example, asked participants to write down as many animals starting with the letter "p" as they could — those who had consumed the omega-3s showed no benefit over those who had not.
Overall, neither the control group nor the test group saw any major decline in cognitive function, however. According to the researchers, this suggests that the time frame of the studies may have been too short to adequately access fish oil’s effect on preventing dementia.
“We really need longer-term studies, which will pick up a greater amount of decline” in cognitive function, Dangour said, but he acknowledged that such studies are expensive and difficult to undertake.
The review's findings were not surprising, because of the limited time frames considered in the studies, said Lynne Shinto, an associate professor of neuroscience who specializes in omega-3 research at Oregon Health and Science University. Shinto agreed with Dangour that long-term studies are needed, but noted that it is difficult to keep people enrolled in such studies for extended periods of time.
Researchers could consider studies of participants who are genetically predisposed to dementia, or are at higher risk of dementia due to health conditions such as diabetes, Shinto said. These might produce more conclusive results over the short term.
An association between eating fatty fish, which is a source of omega-3s in the diet, and cognitive function has been found in previous observational studies, but how the fish provides this brain boost is still unclear. Researchers have found that the benefit exists when fish is consumed broiled or baked but not fried, for example.
Dangour and Shinto agreed that fish oil and omega-3s may have benefits for heart health.
“There is no evidence that taking fish oils has any benefit for cognitive function in later life,” Dangour said, but “people take supplements for a variety of reasons.”
The researchers considered all literature pertaining to the topic but included only the randomized control trials involving older, healthy adults and lasting at least six months. The research does speak to use of omega-3s for people experiencing dementia, they said.
The study was published on June 12 in the journal The Cochrane Library.
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