Omega-6 and omega-3 fatty acids are the two biologically important subgroups of polyunsaturated fatty acids. These compounds get their name because they contain two or more double bonds along their carbon backbone.
While we store most of the fatty acids that we eat as triglycerides in our fat cells, fatty acids are also incorporated into all cell membranes as compounds called phospholipids. Importantly, the ratio of omega-6 to omega-3 fatty acids in our diet is reflected in the ratio in our cell membranes. The correct functioning of our cells requires the same ratio to which humans evolved.
There are many forms of omega-6 and omega-3 fatty acids, but humans can only use a few forms. The bioactive forms have what are called a “parent” fatty acid; the liver can make other omega-6 and omega-3 fatty acids from this “parent” form. Because our bodies cannot synthesize the parent form, they are also often referred to as essential fatty acids. The parent for the omega-3 family is called alpha linolenic acid (18:3n-3; ALA); the omega-6 parent is linoleic acid (18:2n-6; LA). To make them useable by the body, both parent fatty acids are desaturated and chain-elongated in the liver into polyunsaturated fatty acids.
However, the conversion of dietary 18 carbon polyunsaturated fatty acids (PUFA) to longer-chain (> 20 carbon atoms in length) PUFA is an inefficient process. Only about 6 percent of ALA is converted to eicosapentaenoic acid (20:5n-3; EPA) and less still (3.8 percent) is converted to the usable form, docosahexaenoic acid (22:6n-3; DHA).
Furthermore, because omega-3 and omega-6 parent fatty acids must compete for the same enzymes to desaturate and elongate, a high dietary intake of omega-6 fatty acids (18:2n-6) can further reduce the conversion of ALA to EPA and DHA by 40 to 50 percent.
So, it is important to consume sufficient omega-3 fatty acids and not overconsume omega-6 fatty acids.
The typical Western diet is overloaded with omega-6 fatty acids and contains insufficient omega-3 fatty acids; it typically sits around 10:1 in the U.S. In hunter-gatherer diets, however, it was closer to 2:1. This dietary imbalance in fatty acids is a fundamental underlying cause of many chronic diseases, including cardiovascular disease, many cancers, most inflammatory diseases, and many psychological diseases.
There are multiple physiological reasons why this laundry list of illnesses and disease
can be caused by or exacerbated by an imbalance in omega-6 and omega-3 fatty acids. One of the most crucial stems from the synthesis of a type of hormone called eicosanoids, which plays a crucial role in the inflammatory response.
Eicosanoids synthesized from the omega-3 fatty acids (20:5n-3 or EPA) tend to be anti-inflammatory, whereas eicosanoids derived from omega-6 fatty acids (20:4n-6 or arachidonic acid) may promote inflammation in certain tissues. In fact, many over-the-counter pain killers simply block omega-6 derived eicosanoid activity.
Because of the imbalance in the omega-6/omega-3 ratio in the typical Western diet, a chronic state of low-grade inflammation can exist, which in turn may promote many health disorders and diseases.
