CHICAGO (CBS) — A new study has found seafood is still good for your brain, even though the seafood might have mercury in it.

Dr. Martha Clare Morris, a nutritional epidemiologist at Rush University Medical Center, said it appears the mercury found in seafood does not cause people to develop dementia, at least when seafood is eaten at moderate levels – about two or three times per week.

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In fact, the study found moderate seafood consumption could help stave off Alzheimer’s disease.

“There was evidence that seafood consumption of at least one meal per week was associated with less burden of the plaques and tangles that are characteristic of Alzheimer’s disease,” Morris said.

Morris said the results of the study she led were surprising to researchers.

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“We were expecting that, if person had high mercury levels in the brain, that this would lessen the neuroprotection from seafood consumption,” she said.

Seafood involved in the study ranged from salmon to fish sticks; and shellfish such as shrimp, lobster, and crab.

Morris said the study analyzed the brains of 286 people after they died. Subjects who enrolled in the study agreed their brains could be examined after their deaths. They did not have dementia when they joined the study, which began in 1997.

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The study has been published in the Journal of the American Medical Association.