People often ask Jean M. Copeland, RD, CSG, LD, whether fish is brain food. She tells them oily fish is good for your brain.
Copeland is a registered dietitian and certified specialist in gerontological nutrition who provides medical nutrition therapy to patients at Dartmouth Hitchcock Medical Center (DHMC)’s Heart and Vascular Center.
“Oily fish contain two kinds of fats which improve brain health. They are what scientists call long-chain omega-3 fatty acids,” she says. “They may also decrease your risk of developing aortic valve disease.”
Here’s why Copeland says you should consider incorporating oily fish into your diet.
Why is oily fish good for you?
Oily fish—like salmon, herring, sardines, and mackerel—are an excellent source of what is commonly called DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid).
“These fish provide thousands of milligrams of DHA and EPA per three-ounce serving,” Copeland explains, noting that crustaceans and mollusks—like lobsters, oysters, mussels, and scallops—provide hundreds of milligrams per serving, making them a healthy choice, too.
“DHA and EPA are long-chain omega-3 fatty acids that reduce systemic inflammation and become part of your human cell membranes. I call them the ‘universal fire-extinguishers’ because they interrupt several different chemical pathways inside humans which lead to inflammation or these ‘fires,’” she says.
While more research needs to be done, studies suggest that diets high in DHA and EPA are associated with a reduced risk of cognitive decline, Alzheimer’s disease, and dementia.
In fact, DHA is a primary building block of brain cell membranes and is critical for infant brain development and the health of adult brains, where DHA makes up 95% of the omega-3 fats. Because DHA is critical for infant brain and eye development, it is imperative that pregnant moms also consume adequate amounts, Copeland says.
Meanwhile, EPA is beneficial because it competes with the omega-6 fat, arachidonic acid. Many people with rheumatoid arthritis and other painful conditions, for example, feel better when eating more oily fish because of EPA’s ability to interfere with arachidonic acid and its subsequent prostaglandin production, Copeland says.
In addition, DHA turns genes on or off (called gene expression), influencing the activity of inflammatory pathways.
“Both EPA and DHA appear to reduce pain, through different mechanisms,” she says. Together, evidence is strong that EPA and DHA contribute to the prevention of strokes, dementia, major depression, and some types of brain damage.
How do long-chain omega-3 fatty acids help your heart?
Long-chain omega-3 fatty acids are also shown to help decrease the risk of heart disease, Copeland points out.
Studies suggest that a higher consumption of fish that contain DHA and EPA is associated with a lower risk of heart failure, coronary disease, and fatal coronary heart disease.
The American Heart Association (AHA) recommends consuming at least six ounces weekly of oily fish to prevent heart disease.
What about the fact that some fish have mercury in them?
Mercury is a neurotoxin, meaning it is toxic to nerves. "Fish contain mercury in levels commensurate with their age and the amount of mercury in the waters where they live," says Copeland.
To minimize risk, health experts, along with the Environmental Protection Agency, recommend choosing omega-3-rich fish, which have shorter lives, for your daily or weekly meals and snacks. These fish include Atlantic mackerel, salmon, sardines, freshwater trout, and canned light tuna or skipjack. Anchovies are salt-cured, like ham, so are better left as a flavoring ingredient in other dishes.
“Leave the larger fish like King mackerel, marlin, orange roughy, shark, swordfish, tilefish, and bigeye tuna off your plates due to their high levels of mercury,” says Copeland.
One way to think about what fish to eat is to use the acronym “SMASH.”
That stands for Sardines, Mackerel, Anchovies, Salmon, and Herring. These fish are less prone to carry high levels of mercury.
What if you don’t like fish?
“Humans have evolved to meet our EPA and DHA requirements through our diet, and today we have supplements as well,” says Copeland.
Some people think that the omega-3 fats in plants like flax are a comparable substitute to those found in fish. They are not, says Copeland.
“This type of omega-3 fats in plants is not EPA, nor DHA, but rather ALA (alpha-linolenic acid),” she says. “ALA is what is called a short-chain omega-3 fatty acid, which is very poorly converted to EPA, which you want. In fact, less than 5% of ALA converts to EPA by some estimates.”
Once more, some humans lack the genetics to convert even this tiny amount, Copeland points out. So, if you can’t bear eating fish, think about taking fish oil supplements or cod liver oil instead.
Cod liver oil is good because it has both EPA and DHA. “It is also an excellent source of both vitamins A and D. These are important antioxidants which help to maintain health,” concludes Copeland, noting that one teaspoon of cod liver oil contains nearly 1,000 mg of omega-3 in the form of DHA and EPA.
A note of caution from Copeland: Omega-3 fats act as mild antiplatelet substances. If you are already taking antiplatelet medications or anticoagulant drugs of any kind, be sure to make your healthcare provider aware if you add an omega-3 supplement, and monitor yourself for easy bruising. Supplements are not food; they are not metabolized like food, and therefore, they may have unintended consequences if you are not careful.