The Skinny on Fatty Acids

Noah Levine and Simon Evans

Essential fatty acids have become a hot topic. Omega-3 fatty acids have been praised for their health benefits, while omega-6 fatty acids are commonly deemed “unhealthy.” But what exactly are essential fatty acids, and what are the reasons for their respective reputations?

Omega-3 and omega-6 fatty acids are two related dietary fats. Both belong to a family of fats called polyunsaturated fatty acids (PUFAs) and are considered essential, meaning the body cannot synthesize them so you must get them from your diet. The only essential omega-6 is linoleic acid, and the only essential omega-3 is alpha-linolenic acid, which both come from plant oils. We can synthesize all other omega-3s and 6s from them. However, we humans aren’t that efficient at making other important omega-3s, like DHA and EPA, that we can get directly from the oils in fatty fish. 

Numerous health benefits are associated with increased consumption of foods containing PUFAs. These include improved cardiovascular wellness, brain function, mood regulation, and better vision. Mixtures of EPA and DHA have demonstrated a triglyceride lowering effect that is thought to reduce the progression of coronary heart disease. In fact, highly purified EPA and DHA are FDA approved to treat elevated triglyceride levels. Omega-3 fatty acids help reduce chronic inflammation associated with several diseases (e.g., cancer, diabetes, liver disease); omega-6 fatty acids play a role in inflammatory and anti-inflammatory pathways, both of which are important under different conditions. 

So why are omega-3 fatty acids glorified for their health benefits while omega-6 fatty acids have been villainized? The reason is two-fold. First, our diets have changed over the last couple hundred years and we eat about four times the omega-6s than we used to, while at the same time omega-3 intake has declined somewhat–so there is a historical argument that we should be eating more 3s and less 6s. Second, since omega-3s and omega-6s compete for the same metabolic processes that allow them to form the other essential fatty acids, this shifts the balance to a pro-inflammatory state–theoretically. The omega-6, arachidonic acid, which derives from the dietary omega-6, linoleic acid, is involved in various pro-inflammatory processes. The argument goes that more linoleic acid in the diet, more arachidonic acid gets synthesized, more inflammation–-but does this hold? Research has failed to demonstrate that increased dietary linoleic acid results in increased arachidonic acid in the tissues. Arachidonic acid is also used in anti-inflammatory processes; thus, increased consumption may not have a purely negative effect. Numerous studies have demonstrated omega-6 fatty acids being associated with a reduction in cardiovascular disease, especially when replacing saturated fat in the diet. Moreover, increasing omega-3 may be more critical than decreasing omega-6 in the diet.

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