Alzheimer's Risk Lowered with Fatty Acid in Fish

Alzheimer's Risk Lowered with Fatty Acid in Fish

Persons with diets rich in fish have a significantly lower risk of dementia and Alzheimer's disease, according to a report in the Archives of Neurology.

The key appears to be an omega-3 polyunsaturated fatty acid called docosahexaenoic acid (DHA) that is linked to the reduction of dementia risk and appears to be important for the proper functioning of the central nervous system.

"If you have a high level of DHA, a fatty acid found in fish, it reduced your risk of dementia by about half," says study lead researcher Dr. Ernst J. Schaefer, at Tufts University in Boston.

It is known that omega-3 fatty acids protect the heart and the circulatory system.

"Just as fish is good for your heart, it's probably good for your brain as well," says Dr. Schaefer.

Fatty fish like mackerel, lake trout, herring, sardines, albacore tuna, and salmon are high in DHA.

Fish or Fish Oil Supplements Okay

In the study, Dr. Schaefer collected data on DHA levels and dementia in 899 men and women who were part of the Framingham Heart Study.

Over nine years of follow-up, 99 people developed dementia, including 71 with Alzheimer's disease.

The researchers found that persons with the highest blood levels of DHA had a 47 percent lower risk of developing dementia and a 39 percent lower risk of developing Alzheimer's, compared with those with lower DHA levels.

Levels of DHA in the blood vary by how much the liver converts alpha-linolenic acid, an essential fatty acid, to DHA and also by the amount of DHA in the diet, say the researchers.

Persons with the highest blood levels of DHA said they ate an average of two to three servings of fish each week. Persons with lower DHA levels ate substantially less fish

Dr. Schaefer thinks the same benefit can be realized by taking fish oil supplements.

"Everything that we know suggests that supplements would be as effective as eating fish," he says. "Since low fish intake appears to be a risk factor for developing dementia, either eat more fish or use one or two fish oil capsules a day."

However, Dr. Schaefer adds that a randomized clinical trial is still needed to see if DHA really protects the brain from dementia.

Martha Clare Morris, Sc.D., at Rush University Medical Center in Chicago comments in an accompanying editorial, "This is the first study to link blood levels of DHA to protection against Alzheimer's disease.

Dr. Morris, an epidemiologist, explains that recent animal studies have shown that DHA reduces amyloid plaques - a hallmark of Alzheimer's - in the brain and also improves memory.

"There is a lot of animal and biochemical evidence to support what this new study shows," says Dr. Morris.

But, she says, she is not sure there is enough data to suggest the value of fish oil supplements.

"It looks like the protective benefits from omega-3 fatty acids are at a very low level,” she says. “There is very little evidence that you get better protection from higher intake. Whether fish oil supplements are protective is yet to be seen."

Keep Studying, Experts Say

Another expert suggests clinical trials are needed to see if DHA really protects against Alzheimer's.

"This shows in a prospective study that DHA is the only plasma lipid to cut the risk for developing dementia a decade or more later," says Greg M. Cole, Ph.D., at UCLA's David Geffen School of Medicine.

This apparent protection is associated with eating fish, Cole says. "Other studies have pointed to fish intake as protective but have been far less clear that the omega-3 fatty acids in fish were the factor associated with risk reduction.

"This matters because if it is the fat, you could take fish oil supplements and avoid mercury contamination issues," he concludes.

Always consult your physician for more information.