Eating More Fish Reduces Alzheimer's Risk For These People

Eating seafood is good for us, right? Except for those ever-present concerns that the mercury in fish is bad for the humans who eat them, eating fish is generally regarded as a healthier diet than a meat-based one. Researchers at the Rush University Medical Center in Chicago may have just come up with yet another reason to eat seafood. In studying the relationship between mercury and diseases associated with dementia, they found that even as mercury levels rise with seafood consumption, there were no associations with harm to the brain.

In fact, among people with the common genotype (ApoE4) that has been linked to a higher risk of developing Alzheimer's disease, that risk actually diminishes if they eat a moderate amount of seafood.

The study, which ran from 2004 to 2013, focused on about 300 older people living in Chicago retirement homes or subsidized housing. The participants self-reported their fish and seafood consumption among other foods, and after many of them died, their brains were autopsied for research purposes.

The study, published in JAMA, found that the more seafood a person ate each week, the higher the level of mercury detected in their brain when it was autopsied. But those who said they ate seafood one or more times a week also had less Alzheimer’s-related brain pathology, such as plaques or neurofibrillary tangles, compared to those who ate little or no seafood.

Among people with the “e4” version of the apolipoprotein E gene which is linked to a heightened risk of developing Alzheimer’s, the disease was less common for seafood eaters than for those who ate little or none. The results were similar when researchers looked at just omega-3 fatty acid levels in the diet, most of which come from certain types of oily fish.

The participants had normal memory function when they entered the study and kept detailed logs of what they ate. Up to 30 percent of people in the general population have the ApoE4 variant, which puts them at increased risk of developing Alzheimer’s compared to people who don’t have the variant.