Live Science Plus
The Truth About Omega-3 Fatty Acids
Omega-3 fatty acids may come from fish, but there's nothing fishy about their disease-fighting qualities, especially when it comes to your heart.
Omega-3s fall into a category of fat called polyunsaturated fatty acids, and very generally, these are healthier than saturated fats.
But omega-3s and omega-6s are different, and in modern Western diets, omega-6 fatty acids typically outnumber omega-3s by a factor of ten or more. This imbalance is unfortunate, because omega-3s provide a host of health benefits, from anticoagulant effects in the blood to reduced inflammation throughout the body.
Worse, through a feat of molecular malevolence, when omega-6s are overabundant in the diet, they manage to block omega-3s from doing their good work.
Enter the omegas
Fat molecules look somewhat like a jellyfish with three tentacles. Each "tentacle," called a fatty acid, is a long chain of carbon atoms. In saturated fat, the carbon chain is completely coated in hydrogen atoms, forming a straight, rigid configuration. But removing one or more of these hydrogen atoms introduces kinks in the chain, creating a jaggedly-shaped unsaturated or polyunsaturated fatty acid. [Infographic: Different Kinds of Fat Explained]
Omega-3s and omega-6s differ in terms of where in the chain the kinks occur. To return to the jellyfish analogy, in an omega-3, there's a kink three carbons away from the very tip of the "tentacle." Guess where the kink is in an omega-6.
Get the world’s most fascinating discoveries delivered straight to your inbox.
Heartening news
Both omega-3s and omega-6s are essential fatty acids, meaning that your body can't make them, so you have to acquire them through your diet. You need both to survive, and both generally lower LDL ("bad") cholesterol and decrease the risk of cardiovascular disease.
Once you eat them, the body changes them into a variety of useful molecules, but there's a catch: omega-3s and -6s compete for some of the same modification machinery. So if you eat an overabundance of omega-6s, they interfere with your body's ability to use omega-3s.
This competition effect is troubling because among the many uses the body has for omega-3s and -6s, it converts them to signaling molecules called eicosanoids, which promote unhealthy amounts inflammation, blood coagulation, and blood vessel constriction. However, omega-6-eicosanoids promote these unhealthy effects much more than omega-3s.
As a result, people with cardiovascular diseases tend to improve when they add omegs-3s to their diets. Specifically, omega-3s slow the growth of plaque in blood vessels, lower blood pressure, help prevent irregular heartbeats and decrease risk of heart attacks due to blood clots.
According to the American Heart Association, to obtain omega-3s, most people should eat small portions of oily fish twice a week, and people with coronary heart disease should eat fish daily, or talk to a doctor about trying omega-3 supplements.
Other benefits and concerns
Omega-3s have wide-reaching effects beyond the heart. For some conditions, including depression, bipolar disorder, schizophrenia and asthma, scientists are working to conclusively determine whether omega-3s are involved.
For other diseases, however, consumption of omega-3s makes a profound difference. A lack of a specific type of omega-3 found in fish increases risk of Alzheimer's disease. Omega-3s may lower blood serum triglyceride levels, which is beneficial for people who have diabetes mellitus. For those who suffer from rheumatoid arthritis, omega-3s decrease inflammation, and in Crohn's disease, omega-3s may promote longer periods of remission.
Still, omega-3s have some drawbacks. One recent study connected omega-3s with increased risk of prostate cancer. In another small study, researchers found that women who took omega-3 supplements had an elevated cancer risk as well. Additionally, omega-3s may pose health problems for people who are at risk for excessive bleeding, or are taking anticoagulant medications. People with compromised immune systems should also talk to a doctor before supplementing their diet with omega-3s.
The final verdict on omega-3s has yet to be delivered. But in the meantime, a diet rich in omega-3s is a proven way to lower the risk of heart disease, the most common cause of death in the United States.
Foods that have omega-3s
Canola and flax seed oil and walnuts contain some, but not all, of the omega-3 fatty acids. Others can only be obtained from fish such as herring, salmon, sardines, oysters, trout and tuna, or through supplements. Sources of omega-6s include soy, safflower, corn and sesame oil. One way to skew your ratio of omega fatty acids towards omega-3s is to cook with olive oil, which does not contain omega-3s or -6s, instead of vegetable oils like corn oil.
Pass it on: Omega-3s lower your risk for coronary heart disease, the leading cause of death in the United States.