DHA Fish Oil Supplements May Not Help Alzheimer's Patients
November 15, 2010
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.)
These findings don't necessarily mean that DHA has no value at warding off dementia or Alzheimer's, however. Researchers still believe that DHA might help if supplementation is started before the onset of Alzheimer's symptoms, rather than after. "[I]t remains possible that an intervention with DHA might be more effective if initiated earlier in the course of the disease in patients who do not have overt dementia," the authors wrote.
Source: Quinn et al. "Docosahexaenoic Acid Supplementation and Cognitive Decline in Alzheimer Disease." JAMA. 2010;304(17):1903-1911.