A new study found no clear evidence that eating more fish lowers the long-term risk of Alzheimer’s disease.
Researchers used a method designed to more closely mimic a long-term randomized clinical trial.
The findings don’t mean fish isn’t healthy — they suggest it may not be enough on its own to prevent Alzheimer’s.
Fish, particularly oily fish, has long had a reputation as a “brain food.” It contains nutrients such as omega-3 fatty acids, and previous research has suggested that eating fish may benefit brain health. Some observational studies have even linked higher fish consumption with a lower risk of Alzheimer’s disease.
But there’s a catch: People who eat more fish may also differ from those who eat less fish in other important ways. They may have different diets, exercise habits, education levels, incomes, or access to health care, for example. That makes it difficult to determine whether fish itself is responsible for any difference in Alzheimer’s risk.
How researchers put fish to the test
For the new study, researchers from Tufts University used a technique called target trial emulation. The approach uses long-term observational data while applying some of the principles researchers would use in a randomized clinical trial.
The researchers analyzed data from 2,012 cognitively healthy adults in the Framingham Heart Study Offspring cohort. They used the data to emulate a 21-year randomized trial, comparing seven different fish-intake strategies.
The analysis accounted for participants’ diets before the study, characteristics at the beginning of the study, and changes in factors that could influence the results over time. The researchers specifically looked at whether sustained fish intake was associated with developing Alzheimer’s disease over the 21-year period.
So, should you still eat fish?
The researchers found that the estimated 21-year risk of Alzheimer’s ranged from 10.33% among people following a no-fish strategy to 9.98% among those eating at least three servings per week.
Overall, the differences were small, and the study found no clear long-term protective effect from sustained fish consumption. Replacing meat with fish produced similar results.
That doesn’t mean fish should suddenly disappear from your dinner plate. The researchers emphasize that fish remains a healthy food. Instead, the findings suggest that simply eating more fish may not be a standalone strategy for preventing Alzheimer’s disease.
Researchers say future studies should look more closely at factors such as when people consume omega-3s, how their bodies process them, and whether certain genetic or other subgroups may benefit more than others.
“The real advance is that this new research method helps move the field from broad associations to more precise prevention strategies,” researcher José Ordovás said in a news release. “That is the kind of evidence we need if we want dietary guidance to become more personalized, more realistic, and more useful for healthy aging.”