DHA, or docosahexaenoic acid, is a type of omega-3 fatty acid found in fatty fish like salmon, mackerel and sardines. For years, researchers have speculated that fish oil supplements containing DHA might play a role in preventing or delaying the onset of dementia and Alzheimer's disease. A new study, however, finds that DHA may be of limited value for those conditions.
In a randomized, double-blind trial, researchers gave a placebo or a supplement containing 1 g DHA twice a day to people who had been diagnosed with mild to moderate Alzheimer's. Many of the 402 participants received their treatment for 18 months; their cognitive functioning was assessed at the start of the trial and at six-month intervals.
Though blood levels of DHA increased significantly in the group receiving the supplements, there was no significant difference in the rate of cognitive or functional decline between the two groups. Some of the participants also underwent brain MRI scans, but there was also no change in the volume of any part of the brain. (Atrophy in the brain is one of the hallmarks of Alzheimer's disease.)
