Omega-3 supplements fail to reduce Alzheimer’s symptoms

Omega-3 fatty-acid supplements, often called fish-oil capsules, did not curb the mental decline in people with mild to moderate Alzheimer’s disease, researchers said Tuesday. The study marks yet another attempt to treat the disease that has failed in clinical trials.

Treatment with omega-3 supplements had generated considerable enthusiasm because, unlike the other unsuccessful experimental therapies, it was a natural therapy and would not have required development of a new prescription drug. Omega-3 fatty acids were thought to benefit brain health because studies showed that people who included plenty of fish in their diet tended to have lower rates of Alzheimer’s disease. Animal studies, too, suggested the substance might have had an impact.

The study, published in the Journal of the American Medical Assn.,examined 402 people with mild to moderate Alzheimer’s. They were randomly assigned to take 2 grams a day of omega-3 capsules containing docosahexaenoic acid (or DHA) or a placebo capsule. The participants were followed for 18 months, and their cognitive and functional abilities were reassessed. They also underwent MRI to look at the brain. There was no benefit seen in the patients taking omega-3 fatty-acid supplements in either brain volume or cognitive function.

However, among patients taking omega-3 supplements who did not have a particular gene mutation called apolipoprotein (apo) E4, which increases the risk and accelerates the onset of Alzheimer’s disease, there was slightly less cognitive decline. This finding is preliminary and needs to be confirmed, the authors said.

It’s also possible, but unproven, that taking supplements long before symptoms appear might slow progression of the disease.

“We have a very solid but a very negative result,” said the lead author of the study, Dr. Joseph F. Quinn, during a news conference Tuesday in Washington, D.C. Quinn is from Oregon Health and Sciences University and Portland VA Medical Center.

But, he said, evidence has emerged that the symptoms of the disease appear many years after the disease process -- such as the accumulation of amyloid plaques in the brain -- has begun.

“If amyloid is the target,” he said, “the intervention really needs to be very early.”

In an editorial accompanying the study, Dr. Kristine Yaffe noted that progress had been made in identifying the molecular and genetic characteristics of Alzheimer’s disease and in diagnostic techniques. “On the other hand,” she wrote, “little improvement has occurred in the basic care of patients with Alzheimer’s disease and other dementias.”

Related: “Little evidence that anything works to prevent cognitive decline”

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