We call Omega-3 and Omega-6 “essential fatty acids” because the body cannot produce them and needs to obtain them through food. One might ask why, if it’s such an essential element, evolution didn’t favor the selection of individuals capable of synthesizing it, but the way to think about it is the inverse: humans anciently had the capacity to synthesize it but precisely due to economy stopped doing so, optimized to obtain it from the environment where it was abundant at the time, and focused its investment on other more advantageous things.
And it’s not that ancient humans could synthesize it—that genetic use it or lose it occurred already in early vertebrates over 500 million years ago. Since then, an entire branch of the lineage of living beings came to depend on nutrition to obtain these acids.
Seems nonsensical, right? Maintaining complex metabolic pathways is costly. Producing double bonds beyond carbon-9 was a capacity that remained in plants, algae, and some animals, but which the rest subcontracted to the environment.
The next interesting question is: if evolution favored abandoning that metabolic pathway, why do we take omega-3 supplements today if it’s available in the environment? Why omega-3 specifically? And the answer mixes economics and history. During most of human history we consumed omega-3 and omega-6 in our diet in proportions between 1:1 and 1:4. If we measure their proportion in today’s diets, they’re at 1:25. What has changed?
The first thing that changed is that we developed in the late 19th and 20th centuries the technology to extract oil from plants and obtained those marvelous bottles of sunflower oil, soybean oil, etc. These oils are very rich in omega-6 and added large quantities of this element, linoleic acid, to our bodies.
Also produced in parallel was a reduction in traditional fats, either from the cheapening of foods (vegetable oil is cheaper than butter), or from the recommendations of the 1960s that demonized fats without much criteria. Total: more omega-6.
The same process occurred in the meat we eat, which was anciently produced with animals that ate grass and are now fed grain and soy. Omega-6 galore.
And all the shots go that way: we cook less, more ultra-processed food, more seed oils, more omega-6. Secondarily, in many areas humans lost access to abundant fish, either through overexploitation or displacement by cheaper foods that are now available.
Result? The body has an assembly line where omega-3 and omega-6 are processed. And we have it occupied with omega-6, wasting the 3. We have unbalanced input.
The modern way to fix this problem is to supplement omega-3 in typical pills, and it’s interesting to know that with DHA and EPA pills, by giving us directly the omega-3 byproduct that this “assembly line” produces, we bypass the bottleneck. If we take plant-based omega-3 (ALA) we somewhat improve the bottleneck but effectiveness needs more measuring.
One more note: when we talk about olive oil being great compared to other seed oils, it’s because it has much less omega-6, “saturating less.”