Dear Doctors: Our grandfather is having memory problems, and my mom is trying to get him to eat more fish. I know fish is called “brain food,” but my mom says she has heard on that fish keep you from getting dementia. Is this true? What about fish and mercury?
Dear Reader: Research into a link between a diet rich in fatty fish and improved cognitive function dates back decades. The findings continue to point to a wide range of benefits, including improved eye, cardiovascular and brain health.
Research on brain-related effects of consuming fish has found far-reaching benefits that include not only improvements to cognitive function, but also what appears to be protective effects to brain volume and structure. Many of the studies have pointed to the omega-3 fatty acids that certain fish contain, as a factor.
Other research has found a beneficial connection between a diet rich in seafood and the gut microbiome.
Your mother is correct that some research has linked regular fish consumption to a reduced risk of Alzheimer’s disease. One study, based on brain autopsies, found that people who included fish as a regular part of their diets had fewer markers of Alzheimer’s than those who ate little or no fish and seafood.
And, while the people in that study who had consumed more fish did have elevated levels of mercury in their bodies, it wasn’t enough to pose a danger, leading the researchers to conclude the potential benefits outweighed the risks.
Still, mercury in fish is an important issue. It’s a toxic metal that, once consumed, is not eliminated from the body. Negative health effects can include neurological and genetic damage. Mercury is especially damaging to the developing human and to young children. So it’s recommended that eating fish during pregnancy be limited to two servings a week. The same precaution is true for young children, whose developing brains and nervous systems are at highest risk of any damaging effects.
It’s possible to limit the intake of mercury by being selective about the seafood you eat. Steer clear of regularly consuming larger and long-lived fish, such as swordfish, ahi and bigeye tuna, orange roughy, marlin and king mackerel. Their long lifespans mean they have more time to accumulate larger amounts of mercury.
Salmon, ocean perch, shrimp, sardines, scallops, herring, whitefish and flounder are good choices.
The federal Food and Drug Administrations offers a good guide on this. Online, go to fda.gov and enter “advice about eating fish” in the search box.
Dr. Eve Glazier and Dr. Elizabeth Ko are internists at UCLA Health.