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What to Know About Omega-3s and Fish

Experts explain which fish are best for omega-3s, and which you should limit due to mercury.
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WebMD Feature

Fish and omega-3 fatty acids. If you keep up with the latest nutrition news, you may have a pretty good sense of what they offer. But, if you're like many people, you still can't tell your omega-3s from your omega-6s -- and you sure as heck can't pronounce eicosapentaenoic acid. That's OK. Our fishing expedition turned up some interesting facts to share about omega-3 fatty acids and fish.

What Are Omega-3 Fatty Acids?

Omega-3 fatty acids are found in fatty layers of cold-water fish and shellfish, plant and nut oils, English walnuts, flaxseed, algae oils, and fortified foods. You can also get omega-3s as supplements. Food and supplement sources of these fatty acids differ in the forms and amounts they contain.

There are the two main types of omega-3 fatty acids:

  • Long-chain omega-3 fatty acids are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). These are plentiful in fish and shellfish. Algae often provides only DHA.
  • Short-chain omega-3 fatty acids are ALA (alpha-linolenic acid). These are found in plants, such as flaxseed. Though beneficial, ALA omega-3 fatty acids have less potent health benefits than EPA and DHA. You'd have to eat a lot to gain the same benefits as you do from fish.

Fishing for Facts: What Studies Reveal About Omega-3s and Fish

In addition to omega-3s, fish is high in protein, vitamins, and minerals. And, it's low in saturated fat. 

Hundreds of studies suggest that omega-3s may provide some benefits to a wide range of diseases: cancer, asthma, depression, cardiovascular disease, ADHD, and autoimmune diseases, such as rheumatoid arthritis.

How could fatty acids be so beneficial for so many different conditions?

"All these diseases have a common genesis in inflammation," says Joseph C. Maroon, MD, professor and vice chairman of the department of neurological surgery at the University of Pittsburgh School of Medicine. Co-author of Fish Oil: The Natural Anti-Inflammatory, Maroon says that in large enough amounts omega-3's reduce the inflammatory process that leads to many chronic conditions.

For these and other reasons, the Department of Health and Human Services (HHS), the U.S. Department of Agriculture (USDA), the American Heart Association, and the American Dietetic Association recommend eating two 8-ounce servings of fish each week.

The Other Fatty Acid: Omega-6

Unfortunately, the American diet is swimming in omega-6s instead, says Jeffrey Bost, PAC, clinical instructor in the department of neurosurgery at the University of Pittsburgh Medical Center and also co-author of Fish Oil: The Natural Anti-Inflammatory.

"It's in almost everything we eat," he says. "Our diet has shifted away from fresh veggies and fish to foods high in omega-6s, such as crackers, cookies, and corn-fed beef."

Before the introduction of grains, fats, and artificial substances, says Maroon, the ratio of omega-6s to omega-3s was two to one. Today, we consume at least 20 times more omega-6s than omega-3s. The problem is that excessive amounts of omega-6 fatty acids can promote inflammation, a key step in many chronic diseases. 

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