Fish Oil and Seafood for Brain Health: What’s the Evidence?

By Angela Hanson, MD, UW Memory and Brain Wellness Center
April 09, 2018

How do we know what we should be eating to keep our brains healthy? One way is to look at epidemiology studies. This involves studying a group of people over time, surveying what types of foods they tend to eat, and looking at how often they develop Alzheimer’s or other forms of dementia.

Ingestion of fish or fish oil has been studied as a potential way to prevent or treat Alzheimer’s. Fish oil consists of several ingredients but the main two include the free fatty acids DHA and EPA. These are examples of polyunsaturated fatty acids, or PUFAs, and are also called omega-3 fatty acids, because of the structure of the fatty acid chain. People who eat a diet low in PUFA are at higher risk of developing Alzheimer’s disease. In addition, patients with Alzheimer’s have low levels of these fatty acids in their brains. These findings don’t prove that low PUFA diets cause Alzheimer’s, but it suggests that this is an area to study further.

The best evidence for any intervention is a clinical trial: Take a group of people with an illness, give half of them the treatment and the other half a placebo, and look for differences at the end. Several groups have studied whether supplementation with DHA and EPA benefits patients with Alzheimer’s, but with mixed results. When there are mixed results in the medical literature, a group of scientists will often group all of the data together and analyze it in a process called a ‘meta-analysis.’ One such study is the Cochrane Library review in 2016, which found that overall there was no convincing evidence for the use of omega-3 PUFA supplements in treating patients with mild to moderate Alzheimer’s disease. This conclusion was based on high quality evidence and included a lot of different measures of cognition and function. Lead author Marion Burckhardt of the University Halle-Wittenberg, Germany, writes, “It is possible that omega-3 PUFAs improve instrumental activities of daily living, such as more complex activities (i.e. shopping), when taken for a longer period of time, but this has to be confirmed in further trials.” The review also pointed out that side effects were uncommon, so this treatment is likely safe for the vast majority of patients.

Although these PUFA trial results are disappointing, I think the overwhelming epidemiologic evidence still supports eating foods high in PUFAs, such as seafood. One study from 2016 showed that eating just one seafood meal a week over a 12-month period was associated with less decline in certain types of memory and mental processing speed. Seafood in this study was defined as any kind of fish, and it also included shell fish such as shrimp, lobster or crab. The American Stroke Association guidelines already recommend eating fish twice a week for vascular health, and I think we can add ‘cognitive health’ to that as well.