I've been researching several nutritional questions after changing to a plant-based diet and while I've been able to more or less nail down much of my uncertainty, there are a few things that I haven't been able to easily find out. One of these is the matter of Omega-3 fatty acids (FA) in the diet. From what I've read there is some ambivalence about the relative benefits of alpha-linolenic acid (ALA) whereas there is more robust evidence for the beneficial/protective roles of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in regard to chronic diseases such as cancer, insulin resistance and cardiovascular disease. For most people, the main Omega-3 FA obtained from diet is ALA. ALA can be converted to EPA and DHA however in humans the conversion rates seem pretty low, perhaps as low as 5%. This means that even people on a typical diet may be deficient in these longer chain FAs. People can effectively "supplement" their diet through consumption of oily fish which are high in DHA and EPA (which the fish source directly from sea plants). As far as I can tell, DHA and EPA are only available directly from sea plants and not from land plants and thus only ALA is obtained from plant sources in human diets. My question is not about these facts, it is more about the biology at work. As humans are members of the family Hominidae, I assume that at the broad level the nutritional requirements of humans and great apes are very similar. This raises the obvious question of how great apes derive their Omega-3 FAs. Presumably, they simply get ALA from diet and synthesise EPA and DHA from that (few apes go fishing as far as I know). What I am curious about is the conversion rates for great apes. Are they as low as for humans, or are they greater? More exactly, is there any research about nutritional efficiencies of great apes in terms of fatty acids and the comparative health effects? I suppose what I am getting at is that biologically and evolutionarily speaking, why should I be worried about chasing EPA and DHA supplementation on a plant-based diet when it seems that other members of Hominidae seem to be getting along just fine consuming foods that offer ALA only? After all, early humans wouldn't have been fishing cold water fish, and in fact a large percentage of the modern population wouldn't be eating these fish if we hadn't invented fishing trawlers and international supply chains... I have no particular view on this, it's just an obvious question that springs to mind that I haven't quickly found an answer to. Can anyone point me in the direction of research/info that might shed some light on this for me?