By Willow Lawson, published on January 3, 2003 - last reviewed on June 9, 2016
We've known for a few years that people who eat a diet rich in fish are less likely to be depressed. But new research shows that one nutrient in fish might actually be more effective against depression than traditional antidepressants. The nutrient is an omega-3 fatty acid called EPA (eicosapentaenoic acid).
British scientists gave a group of patients with stubborn depression a daily dose of EPA. After three months, over two thirds of the group reported a 50% reduction in their symptoms—particularly feelings of sadness and pessimism, inability to work, sleeplessness and low libido. All of the patients had previously tried other medications, including Prozac, other SSRIs and tricyclic antidepressants, the researchers reported in the Archives of General Psychiatry.
"This is one of the largest potential associations of a nutrient with depression," says Joseph Hibbeln, M.D., a psychiatrist at the National Institutes of Health who has pioneered research into the diet-depression link. "The important issue in this study is that the omega-3 worked above and beyond the antidepressants."
Healthy brains and nerve cells depend on omega-3s because the nervous system is made mostly of fat. The signals that travel through our flesh—feelings, thoughts, commands to our bodies—skip along cells and their arms sheathed in fat.
But not just any fat. Omega-3 essential fatty acids are one of the basic building blocks of the brain. Brain cell membranes are about 20 percent fatty acids and they seem to be crucial for keeping brain signals moving smoothly. Doctors call this class of fat "essential" because, unlike many nutrients, our bodies cannot produce it. We can get it only from very specific parts of our diets.
Found in seafood, also in walnuts, leafy greens and flaxseed, omega-3s are polyunsaturated fats that also protect against cancer and promote cardiovascular health. They may explain why heart disease and depression often occur together.
A growing body of research suggests that seafood can ward off other mental disorders. Countries with diets rich in fish have lower rates of depression, bipolar disorder, postpartum depression and suicide. The complete story of these fats is yet to be told. Scientists haven't nailed down how they interact in the brain with each other, other nutrients and even medications.
The fatty acids in cell membranes need constant replenishment by diet, which seems to be where some complications set in. The omega-3s exist in a delicate balance with another group of needed fats, omega-6s. The trouble is, most Americans are consuming too much of the omega-6s, and they're crowding out the omega-3s. The omega-6s are found in many vegetable oils, such as corn and soy, that permeate processed foods.
Hibbeln says the overabundance of omega-6s in our diet is one of the most critical issues facing U.S. public health. Over the last century, our consumption of soybean oil has increased a thousand-fold, so that each of us now eats about 25 pounds of the stuff a year.
"There's good data that this soybean oil has literally been flooding our bodies and brains," Hibbeln says. He believes that many health problems, including the steep rise in depression, might be due to this radical change in our diet.
So next time you are in the grocery store, take a look at the ingredients on boxes of crackers and cookies and even jars of peanut butter. Most likely they are packed with soybean, cottonseed or corn oil. You might be doing your brain a favor by feeding it a walnut or a sardine instead.
It's too early for prescribing fish as a sure-fire treatment for depression, but Hibbeln says it's a good idea to have some in your diet. Whether fresh or salt-water, all fish contain omega-3s, which originate in the algae and seaweed they eat.
Hibbeln believes the American Heart Association's guidelines are on target for the brain as well as the body: eat seafood, including shrimp, crabs and oysters, two to three times a week for overall health.