Omega-3 DHA boosts memory for healthy adults, not Alzheimer’s sufferers
The results, specific to people with a decline in cognitive function that occurs naturally with age, were presented at the Alzheimer's Association 2009 International Conference on Alzheimer's Disease (ICAD 2009) in Vienna.
Almost 500 people took part in the randomised, double-blind, placebo-controlled, multi-center, six month study, which also recorded improvements in the heart rate of people receiving the DHA supplement. The study was funded by Martek Biosciences.
“In our study, healthy people with memory complaints who took algal DHA capsules for six months had almost double the reduction in errors on a test that measures learning and memory performance versus those who took a placebo,” said Yurko-Mauro, PhD, associate director of clinical research at Martek and lead researcher of the study.
“The benefit is roughly equivalent to having the learning and memory skills of someone three years younger.”
Cognitive decline occurs naturally as we age, and precedes diseases such as Alzheimer's. However, according to other findings also presented at ICAD 2009 in Vienna, the omega-3 fatty acid supplements did not benefit people already suffering from Alzheimer’s disease.
Scientists from Oregon Health and Science University, the University of California, San Diego, Boston University, and Martek report that DHA had no general impact on the cognitive health of people with mild to moderate Alzheimer's.
Implications
“These two studies raise the possibility that [interventions] for Alzheimer's must be given very early in the disease for them to be truly effective,” said William Thies, PhD, chief medical and scientific officer at the Alzheimer's Association.
“For that to happen, we need to get much better at early detection and diagnosis of Alzheimer's, in order to test therapies at earlier stages of the disease and enable earlier intervention,” he added.
Alzheimer’s data
The Alzheimer’s study involved 402 people with an average age of 76, ‘probable’ Alzheimer’s, dietary DHA intakes of no greater than 200 mg per day, and a Mini-mental state exam score (MMSE) between 14 and 26. The participants were randomly assigned to receive a daily DHA dose of 2 grams per day, or placebo, for 18 months.
Results of the double-blind, randomised, placebo-controlled clinical trial, funded by the National Institutes of Health, showed no evidence for benefit in the studied population. Blood levels of DHA did increase, however.
"These trial results do not support the routine use of DHA for patients with Alzheimer's," said lead researcher Joseph Quinn, MD.
In a subset of people who carried the "e4" version of the "ApoE" gene, however, the researchers noted a slower rate of decline on the primary test of mental function (the ADAS-cog). ApoE-e4 is known to increase the risk of developing Alzheimer's but does not appear to modify the rate of disease progression.
"This is an intriguing exploratory result," said Quinn. "However it must be treated with appropriate caution. The finding requires further study for confirmation."
The golden touch on age-related cognitive decline
The Memory Improvement with DHA Study (MIDAS) involved 485 healthy older people with an average age of 70 and a mild memory complaint. The participants were randomly assigned to receive either 900 mg per day of algal DHA or placebo for 6 months.
Results of the randomised, double-blind, placebo-controlled, multi-centre study showed that participants taking DHA supplements made significantly fewer errors on the Paired Associate Learning (PAL) test compared to when they started the study.
Furthermore, plasma DHA levels doubled during the study in the DHA group, and correlated with the PAL response.
The researchers also noted a significant decrease in heart rate in the DHA group, while blood pressure and weight did not change.
“Six month supplementation with DHA (900mg/d) improves memory function and decreases heart rate in healthy older adults with ARCD. This improvement on the PAL is associated with a shift in the normative distribution to a younger age,” wrote the MIDAS investigators.
Sources:
Alzheimer's Association 2009 International Conference on Alzheimer's Disease (ICAD 2009) in Vienna
Presentation #O1-04-02, 12 July 2009
“A clinical trial of docosahexanoic acid (DHA) for the treatment of Alzheimer's disease”
Authors: J.F. Quinn, R. Raman, R.G. Thomas, K. Ernstrom, K. Yurko-Mauro, E.B. Nelson, L. Shinto, A.K. Nair, P. Aisen
Alzheimer's Association 2009 International Conference on Alzheimer's Disease (ICAD 2009) in Vienna
Presentation #O1-04-01
“Results of the MIDAS Trial: Effects of Docosahexaenoic Acid on Physiological and Safety Parameters in Age-Related Cognitive Decline”
Authors: K. Yurko-Mauro, D. McCarthy, E. Bailey-Hall, E.B. Nelson, A. Blackwell, MIDAS Investigators
