Can Seafood Still Be Brain Food?
What to do when the brain-healthiest food is also a top microplastic accumulator
Seafood has long been hailed as a top brain food given that it’s rich in omega-3s that sharpen memory, boost mood, and protect against cognitive decline. In fact all of the proven brain-protective dietary patterns recommend eating one or more servings of some type of seafood each week. And yet, we can’t ignore the fact that as our oceans fill up with plastic, so do the fish and seafood we eat.
All this month on the newsletter we have been shining our brain health lens on environmental toxins. Microplastics, as I wrote last time, are stressing us out. Not only are they accumulating in the brain far more rapidly than 20 years ago, these tiny toxins may be shaping neurologic health in ways we have yet to define.
For today’s newsletter, let’s take a fresh look at the pros and cons of eating seafood. We’ll examine how seafood earned its stripes as a top brain food. I’ll share recently published data on this food group’s impact on dementia risk. Plus, we’ll take a look at how seafood stacks up as a threat to the microplastic accumulation in our brains.
This is the fourth in our mini-series about the impact of environmental toxins on brain health. Catch up with these posts:
Microplastics in Food and Drink
Almost everything you eat or drink will contain microplastics. That’s a harsh reality of modern life. This graph is helpful to see where fish and seafood lie on the spectrum of microplastic exposure, measured in grams of particles per liter per meter cubed. As you can see, water, beer, and air deliver far more of the tiny toxins, but seafood is high on the list compared to other foods.
Microplastic math
It’s no surprise that seafood is at the top of the list of contaminated foods. After all, sea creatures are taking the biggest hit for our plastic problem by living on the front line: polluted oceans and freshwater. This study in Environmental Science and Technology estimates Americans consume up to 100,000 or more microplastic particles annually from air, water, and food. Of this, an estimated 39,000–52,000 particles come from food alone. How much of this is from fish? Let’s do the math.
Based on the microplastic accumulation in bivalves and small whole fish (which is greater than other fish), the microplastic concentration is about 1 particle per gram. One 4-ounce (113 gram) serving harbors about 113 particles. What does this mean if you’re following the recommended one to three servings of fish and other seafood a week? Between 5,866 and 17,600 microplastic particles per year.
If you eat seafood once a week, 5,866 particles per year makes up around 5% of your total microplastic exposure. It’s significant, but not nearly the amount we get from bottled and unfiltered water.
And still, seafood makes up enough of the microplastic load to make it a food of concern. The question is: Does the brain health benefit of eating fish still outweigh the potential harm?
How fish and seafood became a brain food
All of the proven brain-protective dietary patterns include fish and seafood. This food group is the predominant protein in the Mediterranean diet. It made the list of the 10 brain-healthy food groups in the MIND diet study, too. And, it holds a spot in the BHK Food Guidelines on page 32 of my book as a top ten brain food.
Current guidelines for eating fish and seafood in a brain-healthy diet:
Mediterranean: Three servings per week, each 3 to 4 ounces.
MIND: One or more 3-ounce servings per week.
BHK: One or more 3-ounce servings per week.
To earn a spot on these brain-specific food guidelines, a food has to have accumulated sufficient data to show a significant impact on reducing dementia risk. Simply put, people who eat fish and seafood are 30 to 60% less likely to develop dementia than non-eaters. This is based on dozens of studies, albeit most of them observational. Here are a few of the landmark ones:
Rotterdam Study: This study of 5,386 Dutch adults over age 55 was the first study to show that diets high in saturated fat increased the risk of dementia. It also showed that higher fish consumption was associated with a 60% reduced risk of dementia and Alzheimer’s. Kalmijn et al. Annals of Neurology, 1997.
Chicago Health and Aging Project: People who ate fish at least once a week had a 60% lower risk of Alzheimer’s disease compared to those who rarely or never ate fish. Morris et al, JAMA 2003.
Framingham Heart Study: Higher plasma DHA levels (from fish intake) were linked to a 47% reduced risk of developing dementia over 9 years. Tan et al., JAMA 2005.
PAQUID Study: This study of 1,416 older French adults found that eating fish once a week was associated with a 35% lower risk of dementia over 7 years. Barberger-Gateau et al., BMJ, 2002.
Fish Consumption and Grey Matter Study: Higher fish consumption was associated with greater gray matter volume in key brain regions (based on MRI brain imaging) and less Alzheimer-type pathology (based on autopsy data). Raji et al, Am J Prev Med, 2015.
MIND Diet Study: Eating one or more serving of fish (not fried) each week as part of the MIND diet was associated with a 53% reduced risk of developing Alzheimer’s disease over 4.5 years. Morris et al, Alzheimer’s & Dementia, 2015.
In addition, there have been several more recent studies published about the relationship between eating fish and dementia risk. This 2021 Japanese study showed that a high intake of fish at midlife protects the brain from dementia up to 15 years later. This 2025 meta-analysis of 35 studies found that daily fish eaters had 18% lower dementia risk and up to 30% lower Alzheimer’s disease risk. And this 2021 study from China showed a 20 to 30% reduction in dementia risk in people who ate fish compared to those who did not. Fatty fish (high in omega-3 fats) yielded greater dementia risk reduction than lean fish.
What about mercury, a heavy metal common in fish that’s a known neurotoxin?
In this study of 286 brain autopsy specimens, Dr. Martha Clare Morris and her team at Rush University looked at the relationship between eating fish, brain mercury levels, and Alzheimer's disease. The study found that while eating fish was associated with higher brain mercury levels, it was also correlated with less Alzheimer's-related brain damage, especially in those who carry an ApoE4 risk gene. In other words, participants had less Alzheimer’s disease the more fish they ate despite accumulating mercury.
As you can see, there is a lot of data that supports eating fish and seafood to protect the brain from dementia. Even mercury-laden fish is associated with better brain outcomes.
My Takeaway on Microplastics in Seafood
It’s too early to say if microplastics cancel out some of the benefits of including fish and seafood in a brain healthy diet. Scientists are still trying to determine if these plastic particles accelerate cognitive decline or if they are more likely to accumulate in a brain that already has dementia.
Will microplastics prove to put a meaningful dent in the whopping 30 to 60% dementia-reducing impact of eating seafood? It will take years for researchers to sort this out. Based on what we know now, not eating seafood would cause greater harm than any potential risk associated with microplastic exposure.
Here’s what we can do now
For now, I am not changing how much seafood I eat because of the microplastic factor. I do resolve, however, to incorporate the latest microplastic science into my seafood choices.
Here’s what we can do based on what we know now: choose safer, less contaminated, fish and seafood.
Next time, we’ll look at how to choose safer fish. I’ll provide a list of different types of fish ranked by how much microplastic it carries. And did you know there are practical tips for prepping fish to reduce exposure? I’ll cover that, too, along with the most brain-healthy cooking techniques. And, we’ll take a closer look at the issue of heavy metals and other pollutants in fish with regard to brain health.
Until then, please accept my thanks for reading, sharing, and taking the best care of your brains. If this post was helpful, please share, restack, or tap on the heart. Doing so helps BHK reach more brains.
Love,
Annie
Brain Health Retreats Update
Want to join me on a Brain Health Retreat this year? Your brain will thank you! For detailed information about each trip, click on the links below or tap on RETREATS on the homepage.
Sardinia’s Secrets For a Long and Healthy Life, October 12 to 19, 2025. This fall I am headed back to Italy to explore Sardinia’s blue zones. Find all the details here; call 877-298-9677 for more information and to reserve your spot. This Brain Health Retreat was featured in National Geographic Traveller UK.
Costa Rica in February 5 to 10, 2026: Fitness + brain health in the jungle by the beach! This retreat is 100% plant-based and alcohol-free. Learn more and reserve your spot here. Just 1 cabaña left!
Looking for a spring trip in 2026? I’ll be announcing a new retreat soon.
Thank you for this super informative post, Annie!!
I hope you’ll include specific brands of canned fish that are recommended, if possible. 😊
Thanks so much for this article. It’s very helpful to me and I can’t wait to read more about fish choices and preparation.