The February 2010 issue of the American Journal of Clinical Nutrition contains a new report by Alexander Ströhle, Andreas Hahn and Anthony Sebastian, entitled Estimation of the diet-dependent net acid load in 229 worldwide historically studied hunter-gatherer societies.
They conclude that 40-50% of those 229 hunter-gatherer groups listed in the Ethnographic Atlas ate diets that had a net acid residue, due to the reliance on animal protein.
In the same issue, S. Boyd Eaton, Melvin Konner, and Loren Cordain published an editorial response entitled "Diet-dependent acid load, Paleolithic nutrition, and evolutionary health promotion".
Eaton et al point out that humans evolved in Africa, where the typical hunter-gatherer diet supplies 50% of calories from animal sources and 50% from plant sources, and has a net alkaline residue as a result. They argue that this sets the standard for human nutrition, and that deviations from this occured in many recent hunter-gatherer diets. In their words:
As humans migrated over the globe and cultures changed, nutrition increasingly diverged from the ancestral pattern. Genetic evolution was unable to keep pace, and, consequently, various pathologies developed (6). In contemporary affluent nations, complex degenerative diseases such as atherosclerosis, numerous cancers, and hypertension reflect discordance between ancient genes and current diets, whereas the "epidemics" of obesity and diabetes can be largely attributed to our unholy (and unpaleolithic) alliance of sedentism and hypernutrition (7).
The striking prevalence of osteoporosis in Inuit skeletal remains from the early contact period (8) is especially pertinent to the observations of Ströhle et al (1) because plant foods are necessarily scarce in circumpolar environments. In East Africa, late Paleolithic plant-to-animal energy intake ratios would have approximated 50:50, and diet-dependent net endogenous acid production (NEAP) would have been alkaline—the norm for human biochemistry, physiology, and bone health. In contrast, for traditional Inuit HGs, whose subsistence derived overwhelmingly from aquatic and animal sources, NEAP would have been acidic, contributing to their osteoporosis.
So, they argue that the high rate of osteoporosis among Inuit demonstrates that humans are adapted to an African hunter-gatherer diet high in plant foods that would provide alkaline residues. To document the incidence of osteoporosis among the Inuit, Eaton et al cited a paper by Richard Mazess entitled "Bone Density in the Sadlermiut Eskimo", one I have seen cited before for this purpose.
So, I received the Mazess paper today, and I was astounded to read it. This paper did not demonstrate a high incidence of osteoporosis among Inuit. Mazess compared the bones of the pre-contact Inuit to bones of Americans and Peruvians. He reported:
Mazess also states:
"The ash percentage in the Sadlermiut Eskimo bone sections is significantly higher than from most those other samples examined..."
However, the samples from the Eskimos were from considerably younger individuals than the American samples:
Mazess explores a nutritional explanation for the elevated bone density of the Eskimos and finds it a little wanting:
Anyway, this exercise demonstrated again how hearsay gets passed around the scientific community. It seems likely that neither Eaton, Konner, nor Cordain read the Mazess article, or they would have realized that it did not support their claim of lower bone density among Eskimos. Like me, they must have seen this article cited before as support for the claim, but never took the time to read it.
The Mazess paper does not demonstrate osteoporosis among the Eskimos, nor does it demonstrate stronger bones among Eskimos. It placed the Eskimos in an intermediate position, and since they were younger bones, we can't know how older Eskimo bones looked.
I will add that we can't reliably use the bone mass of exhumed ancient bones to claim high bone masses for hunter-gatherers. This evidence suffers from survivor bias. Over long periods of time, stronger bones are more likely to survive than weaker bones. We unearth the strong bones, and conclude that all ancient people had strong bones; but we don't see all the bones that did not survive the passage of time and weather, etc. The weak bones don't get counted because they didn't survive!
Check the references!
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