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What Are Omega-3 Fatty Acids?

(Image credit: Korzeniewski | Dreamstime)

Foods such as eggs, bread and milk are often enriched with the elusive, yet much-touted for their health benefits, omega-3 fatty acids. These are polyunsaturated acids basically, long chains of carbon atoms and hydrogen atoms strung together, with an acid molecule at one end of the chain.

They're tiny. If you were to stretch these chains out and line them up end to end, more than 2 million omega-3 acids would be as big as an exclamation point, or about 0.25 inches (0.64 centimeters) long!

But even with such a small size, these chains certainly boast big health benefits. According to the Mayo Clinic, omega-3 fatty acids are thought to reduce inflammation in the body, improve learning ability in children, decrease triglycerides, lower blood pressure, reduce blood clotting, enhance immune function and improve arthritis symptoms.

What are they

The three most common omega-3s used in the human body are: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).

Each of these molecules is made of carbon, hydrogen and oxygen, but they differ in the length of their chains and number of double bonds. For example, EPA has 20 carbon atoms in its chain and five carbon-carbon double bonds; DHA includes 22 carbon atoms and six carbon-carbon double bonds. (The 3 in omega-3 indicates that the first double bond in the chain is on the third carbon.)

The body needs ALA because it can't produce it on its own, but it can convert ALA into EPA and DHA. Omega-3 acids and their cousins, omega-6 acids, are found in fish oil and vegetable sources, including flax and hemp seeds.

While omega-3s are thought to play a role in treating and preventing diseases, the effect is hard to measure. There isn't one definitive study that says eating a certain amount of omega-3s reduces your risk of a specific disease by a certain percent. Instead, there are many studies, and reviews of these studies, that point toward a general belief that omega-3s are good for your health.

For example, the Office of Dietary Supplements of the National Institutes of Health (NIH) reviewed eight studies on the effects of omega-3s in treating several diseases, including cardiovascular disease, asthma and diabetes. Key findings include: Consuming omega-3s reduces mortality and certain risks for cardiovascular disease (with some caveats); omega-3s are involved in cells' functions necessary for a normal heart rate; and evidence is inadequate to determine the effect of omega-3s on mental health.

How to get enough

There are no hard-and-fast rules on how much omega-3s to consume. The American Heart Association recommends eating at least two servings a week of fish, in part because of its omega-3 content.

The Institute of Medicine of the U.S. National Academy of Sciences published "Adequate Intake" level for ALA of 1 to 2 grams per day. (An Adequate Intake level indicates the amount of a nutrient that appears to support good health and is used when there isn't enough information to set a recommended daily amount, or RDA.) A typical serving of fish contains about 0.2 grams of ALA; a tablespoon of flaxseed oil contains 7 grams of ALA.

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Michelle writes about technology and chemistry for Live Science. She has a Bachelor of Science in Chemistry from the Salisbury University, a Bachelor of Chemical Engineering from the University of Delaware and a degree in Science Journalism from New York University. She is an active Muay Thai kickboxer at Five Points Academy and loves exploring NYC with friends.