Study: No omega-3 effect on Alzheimer's patients
November 3, 2010
PORTLAND, ORE. — Supplementation with an omega-3 fatty acid sourced from algae did not slow the rate of cognitive and functional decline in patients with mild to moderate Alzheimer’s disease, according to results of a study appearing in the Nov. 3 issue of The Journal of the American Medical Association. Docosahexaenoic acid (DHA), the omega-3 fatty acid used in the study, is the most abundant long-chain polyunsaturated fatty acid in the brain.
The study looked at the use of omega-3 fatty acids as a treatment for people who already have Alzheimer’s disease, but omega-3 fatty acids also may have a neuro-protective effect on the prevention of developing Alzheimer’s disease, said Harry Rice, vice-president of regulatory and scientific affairs for the Global Organization for EPA and DHA Omega-3s (GOED).
“We advocate for ingestion of long-chain omega-3s throughout the life span,” he said.
He said the study was well-conducted and used human subjects while other omega-3 fatty acid studies on Alzheimer’s disease have used animal subjects.
“In general, I think it was very good,” said Dr. Rice. “I think it answered a lot of questions, and good research always leaves more questions to be answered.”
Dr. Rice said he hoped media coverage of the study would not turn consumers away from omega-3 fatty acid ingestion.
“With the benefits of long-chain omega-3 fatty acids, there is no reason why people shouldn’t be taking them, getting them through their diet,” he said. “The cardiovascular benefits are incredible.”
Joseph F. Quinn, M.D., of the Oregon Health and Science University in Portland, was the corresponding author for the study. Two of the doctors involved in the research were employees of Martek Biosciences, Columbia, Md., a manufacturer of DHA and the supplier of the placebos and DHA used in the study. A grant from the National Institute on Aging supported the study.
Previously, animal studies have demonstrated oral intake of DHA reduces Alzheimer-like brain pathology. The new study was conducted at 51 U.S. clinical research sites of the Alzheimer’s Disease Cooperative Study. The randomized, double-blind, placebo-controlled trial of DHA supplementation involved individuals with mild to moderate Alzheimer’s disease. While 402 people were randomized for the study, 295 of them completed the trial.
People randomly were assigned to algal DHA at a dose of 2 grams per day or to identical placebos. Treatment lasted for 18 months.
Researchers used the Alzheimer’s Disease Assessment Scale (ADAS-cog) and the Clinical Dementia Rating (CDR) sum of boxes. The ADAS-cog is a 70-point scale that evaluates memory, attention, language, orientation and praxis, with higher scores indicating greater impairment. The CDR sum of boxes is a global measure assessing memory, orientation, judgment and problem solving, community affairs, home and hobbies, and personal care.
Supplementation with DHA had no beneficial effect on rate of change on ADAS-cog score, which increased by a mean of 7.98 points for the DHA group during the 18 months versus 8.27 points for the placebo group. The CDR sum of boxes score increased by 2.87 points for the DHA group during 18 months compared with 2.93 points for the placebo group.
As expected, plasma phospholipid DHA increased in the DHA treatment group from 3.18 weight percentage at baseline to 9.80 weight percentage at 6 months, 10.20 weight percentage at 12 months and 9.82 weight percentage at 18 months. The placebo group had no significant change in plasma phospholipid DHA.
“Despite enrollment of the target population of individuals with low baseline DHA, increase of plasma phospholipid and cerebrospinal fluid DHA in the group treated with DHA, and ample progression of randomized participants on the primary outcome measures, there was no evidence of benefit of DHA supplementation in this population,” the researchers said.
The Council for Responsible Nutrition, a trade association for the dietary supplement industry and based in Washington, said it believes more research should be conducted with respect to DHA’s role in reducing the risk of Alzheimer’s disease and dementia.
“The concern with this study is that it focused on supplementing DHA in individuals who were currently coping with Alzheimer’s disease,” said Duffy MacKay, vice-president, scientific and regulatory affairs for the CRN. “It didn’t answer the question of whether DHA — taken over long periods of time and several years prior to disease onset — could have helped prevent these participants from developing the disease.
“Further the study only tested DHA under the assumption that it could be used as a treatment, which is highly unlikely given how little we know about Alzheimer’s disease. There is still much to be learned about the potential of DHA —and all omega-3 fatty acids — and the many health benefits they offer consumers.”