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NIH Study Shows No Benefit of Omega-3 or Other Nutritional Supplements for Cognitive Decline
While some research suggests that a diet high in omega-3 fatty acids can protect brain health, a large clinical trial by researchers at the National Institutes of Health found that omega-3 supplements did not slow cognitive decline in older persons. With 4,000 subjects followed over a 5-year period, the study is one of the largest and longest of its kind. It was published on August 25 in the Journal of the American Medical Association.
“Contrary to popular belief, we didn’t see any benefit of omega-3 supplements for stopping cognitive decline,” said co-author Emily Chew, MD.
Chew leads the Age-Related Eye Disease Study (AREDS), which was designed to investigate a combination of nutritional supplements for slowing age-related macular degeneration (AMD), a major cause of vision loss among older Americans. That study established that daily high doses of certain antioxidants and minerals — the so-called AREDS formulation — can help slow the progression to advanced AMD.
A later study (AREDS2) tested the addition of omega-3 fatty acids to the AREDS formula. But the type of omega-3 made no difference. Omega-3 fatty acids are made by marine algae and are concentrated in fish oils; they are believed to be responsible for the health benefits associated with regularly eating fish, such as salmon, tuna, and halibut. Where studies have surveyed people regarding their dietary habits and health, they have found that regular consumption of fish is associated with lower rates of AMD, cardiovascular disease, and possibly dementia. “We’ve seen data that eating foods with omega-3 may have a benefit for eye, brain, and heart health,” Chew commented.
Omega-3 supplements are available over the counter and are often labeled as supporting brain health. A large 2011 study found that omega-3 supplements did not improve the brain health of older patients with pre-existing heart disease.
With the AREDS2 study, Chew and her colleagues saw another opportunity to investigate the possible cognitive benefits of omega-3 supplements, she said. All of the participants had early or intermediate AMD. Their average age was 72 years, and 58% were female. The subjects were randomly assigned to one of four treatment groups:
- Omega-3 (specifically docosahexaenoic acid [DHA], 350 mg) and eicosapentaenoic acid (650 mg)
- Lutein and zeaxanthin (nutrients found in large amounts in green leafy vegetables)
- Omega-3 and lutein/zeaxanthin
Because all of the participants were at risk of worsening of their AMD, they were also offered the original or a modified version of the AREDS formulation (without omega-3 or lutein/zeaxanthin).
The participants were given cognitive-function tests at the beginning of the study to establish a baseline, and then 2 and 4 years later. The tests, all validated and used in previous cognitive-function studies, included eight parts designed to test immediate and delayed recall, attention and memory, and processing speed. The cognition scores of each subgroup decreased to a similar extent over time, indicating that no combination of nutritional supplements made a difference.
“The AREDS2 data add to our efforts to understand the relationship between dietary components and Alzheimer’s disease and cognitive decline,” said Lenore Launer, PhD, senior investigator in the Laboratory of Epidemiology and Population Science at the National Institute on Aging. “It may be, for example, that the timing of nutrients, or consuming them in a certain dietary pattern, has an impact. More research would be needed to see if dietary patterns or taking the supplements earlier in the development of diseases like Alzheimer’s would make a difference.”
Source: NIH; August 25, 2015.