If you have seen a baby formula pack, it highlights in bold that the formula is fortified with EPA and DHA and that it’s good for brain development. The long chain Omega fatty acids, EPA and DHA are essential to humans for brain development, controlling inflammation and immune system performance.
People who are non-vegetarians acquire these directly from the meat and fish they eat. Since vegetarians are unable to get EPA and DHA, their bodies must develop a way of producing those from the plant based diets they eat. It turns out that over thousands of years, this has change has taken place in the bodies of people whose ancestors had been vegetarians. These people are able to produce EPA and DHA from plant based foods, whereas bodies of people whose ancestors were non-vegetarians, do not have this ability.
[Example of evolutionary adaptation: Bodies of people whose ancestors have been living in hot and sunny places for thousands of years have a darker skin tone because their bodies produce more melanin to protect them from sunlight. Bodies of people whose ancestors have been living in cold and less-sunny places for thousands of years have a lighter skin tone because their bodies produce less melanin to produce more vitamin D. This is known as adaptation. If subsequent generations of people are exposed to the same environment, they tend to adapt to the foods that are available in that environment. This happens over hundreds of generations].
Regarding vegetarian and non-vegetarian adaptation, a Cornell University study found such an adaptation occurring in humans via a gene called FADS (FADS1 and FADS2). There is a vegetarian and a non-vegetarian version of this gene. The vegetarian version is great at producing EPA and DHA from plant sources, whereas the non-vegetarian version is not. The consequence is that- if you are a non-vegetarian shifting to a vegetarian diet, you should pay attention to your EPA and DHA needs and adequately supplement.
The FADS1 gene found in the ancestral vegetarian farmers produces enzymes that play a vital role in the biosynthesis of omega-3 and omega-6 long-chain polyunsaturated fatty acids (LCPUFA). While omega-3 and omega-6 can be obtained directly from animal-based diets, they are absent from plant-based diets. Vegetarians need FADS1 enzymes to biosynthesize LCPUFA from SCPUFA found in plants (roots, vegetables and seeds).
There is also a consequence to carriers of the vegetarian version of the FADS1 gene, shifting to non-vegetarian diets. Possibly due to excessive omega’s in the system shifting the omega 3 to omega 6 ratio, they may be at higher risk of heart disease and cancer. So, if you are making that shift, moderate your non-veg intake.
More importantly, it will help you to find out which version of the FADS1 genes you carry to understand whether your body is optimized for EPA and DHA via vegetarian or non-vegetarian sources.