Monday, October 17, 2016
Humanity's fishy origins
I am just back from a sequence of speaking engagements at scientific conferences in and around Cape Town, South Africa and, as fate would have it, a quick and illuminating trip to the Stone Age.
That unexpected detour came courtesy of Professor Frits Muskiet of the University of Groningen, The Netherlands. Prof. Muskiet, a clinical chemist extensively published in the area of fatty acid metabolism, was among the plenary speakers at the ISSFAL (International Society for the Study of Fatty Acids and Lipids) 2016 Congress, as, indeed, I was honored to be. He took advantage of the occasion to deliver a talk in equal measure erudite and entertaining in the area of evolutionary medicine, and human adaptations to particularly patterns of dietary fat intake.
The question with which Prof. Muskiet especially wrestled was this: why should humans, with alleged origins in the savannas of Africa, have adapted a need foromega-3 fats? If the question sounds at all odd to you, it should not. Creatures adapt to need what their environment provides, or they make a hasty retreat from living at all. It is not happenstance, for example, that all of the vitamins and minerals we discover to be essential in some way to human metabolism are found on this planet. The same may be said of the gases we breathe.
Stated differently, if we have evolved a dependence on omega-3 fatty acids in our diets- a fact indicated by the categorization of these among others as “essential” fatty acids- then omega-3 fats must have been part of the nutritional habitat in which humans evolved. Where, then, were these fats now routinely called “fish oil” coming from on African savannas?
My answer has long been from the flesh of wild game that is to the flesh of grain-fed, domestic cattle as saber-tooth is to tabby. This is by no means an argument of my own devising. Rather, just this is suggested by the seminal, peer-reviewed papers on Paleolithic nutrition, now spanning several decades.
Among others, Boyd Eaton, whose work and insights I have gratefully acknowledged before, and colleagues have suggested stark differences between the meat that prevails in modern societies, and the meat consumed by our hunter-gatherer forebears. In brief, well over 30% of the calories in modern beef come routinely from fat, much of it saturated, and effectively none of it omega-3. In contrast, the flesh of antelope, thought roughly approximate to that of favored Stone Age game, derives as little as 7% of total calories from fat, little if any of it saturated, and a meaningful portion of it omega-3.
The simple conclusion is that what we now call fish oil- the long-chain omega-3 fatty acids, EPA and DHA- has been domesticated out of terrestrial animals by adulterating the composition of their diets. As other presentations at the ISSFAL conference suggested, we are at risk of doing the same to fish by altering their diets in aquaculture.
Prof. Muskiet allowed for this when I asked him about it, but he made a compelling, parallel case. Citing the work of various paleoanthropologists and archaeologists, and tracing findings through the stages of human ancestry, his argument was that humanity has long favored life at a land/water interface. Much of this involved lakes and rivers, and sourcing shellfish from tidal flats. Quite ancient archeological sites indicate human, and even pre-human, consumption of mussels and other mollusks. Fishing hooks many thousands of years old suggest that even fish from the sea figured in the human diet long before the dawn of agriculture.
We may, and indeed must, allow for substantial uncertainty regarding our habitual dietary intake tens of thousands of years ago. Most of us struggle to recall what we ate yesterday with any degree of fidelity. But we must also accommodate the truism that what we now require in our diets is what we adapted to eat. Omega-3 is an essential dietary requirement, and that requirement came from our long, pre-agricultural evolutionary history. Argument one is that it came by land, and argument two is that it came by sea. Let's take the easy way out and allow for either, or both, and continue from there.
There are two important implications of our omega-3 requirement. The first is that popular expressions of the Paleo fantasy that emphasize the fatty meats of land animals are woefully misguided. Seldom does one see ardent proponents of Stone Age dietary patterns emphasize fish, let alone mussels, to say nothing of the arduous daily exertions and estimated 100 grams of daily fiber that were also thought to figure in it. Rather, the Paleo “brand” has been corrupted into pop-culture nonsense, and an invitation to eat more bacon.
The second, of course, is that we all need omega-3 in our diets, and many of us need more- for optimal balance, if not to avoid overt deficiency- than we routinely get. How best to address that?
We have 3 options. The first is to get our omega-3s from plant sources, such as flax, walnuts, and seaweed. This, however, provides mostly for ALA, a short-chain omega-3 we convert into EPA and DHA with variable efficiency. ALA is good for us in its own right, but it is somewhat unreliable as a source of the long-chain omega-3s so important to our vitality in various ways.
The second is to eat fish and seafood routinely. There are many good arguments for this approach, but an important one against it: 8 billion hungry Homo sapiens are decimating the world's fisheries. We go this route with sustainability always in mind, or we go there at our peril.
The third is to take supplements, for which the sustainability of sourcing, be it fish, or krill, or mussels, is again a salient concern.
These options are, of course, not mutually exclusive. They can be combined in various ways, and for whatever it's worth, I rely personally on all three.
As for sustainability, there are excellent resources to guide our selections, and industry is under increasing pressure to make this a priority. With increasing attention to the matter on the part of both demand and supply, we have hope of getting our omega-3, and keeping fish in the sea, too.
But the main point here is simply that a realistic understanding of our Paleolithic proclivities leads us toward omega-3s in the first place. Almost paradoxically, those of us who find ourselves most routinely in argument with the ardent proponents of contrived distortions of the Paleo diet are often ardent proponents of the relevance of the real Paleo diet. I certainly am, having closely followed the literature on this topic for nearly three decades. If native diet and adaptations to it are relevant to the basic care and feeding of every other species on the planet, as they clearly are, what preposterous hubris to think them irrelevant to us. Efforts to probe, and honestly portray, our own primal diet are accordingly of immanent value.
The sad reality, though, is that prevailing pop-culture expressions of Paleo devotion are much about salesmanship, and not at all about scholarship. Mussels and mammoth are Paleo; bacon, baloney and lard- are not. Whatever the temptations of telling people what they want to hear, you simply can't make a polyester purse from a woolly mammoth's ear.
David L. Katz, MD, FACP, MPH, FACPM, is an internationally renowned authority on nutrition, weight management, and the prevention of chronic disease, and an internationally recognized leader in integrative medicine and patient-centered care. He is a board certified specialist in both Internal Medicine, and Preventive Medicine/Public Health, and Associate Professor (adjunct) in Public Health Practice at the Yale University School of Medicine. He is the Director and founder (1998) of Yale University's Prevention Research Center; Director and founder of the Integrative Medicine Center at Griffin Hospital (2000) in Derby, Conn.; founder and president of the non-profit Turn the Tide Foundation; and formerly the Director of Medical Studies in Public Health at the Yale School of Medicine for eight years. This post originally appeared on his blog at The Huffington Post.
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