Paleolithic nutrition: what can we learn from the past?

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Paleolithic nutrition: what can we learn from the past?

Mann NJ.

Department of Food Science, RMIT University, Melbourne, 3001,

Australia.

Asia Pac J Clin Nutr. 2004;13(Suppl):S17.

Background - Anthropologists and some nutritionists have long

recognised that the diets of Paleolithic and recent hunter-gatherers

(HG) may represent a reference standard for modern human nutrition

and a model for defense against certain western lifestyle diseases.

Boyd Eaton of Emory University (Atlanta) has spent over 20 years

reconstructing prehistoric diets from anthropological evidence and

observations of surviving HG societies, put this succinctly: " We are

the heirs of inherited characteristics accrued over millions of

years, the vast majority of our biochemistry and physiology are tuned

to life conditions that existed prior to the advent of agriculture

some 10,000 years ago. Genetically our bodies are virtually the same

as they were at the end of paleolithic some 20,000 years ago. The

appearance of agriculture and domestication of animals some 10,000

years ago and the Industrial Revolution some 200 years ago introduced

new dietary pressures for which no adaptation has been possible in

such a short time span. Thus an inevitable discordance exists between

our dietary intake and that which our genes are suited to " . This

discordance hypothesis postulated by Eaton, could explain many of the

chronic " diseases of civilisation " . But what did hunter-gatherer

populations actually eat? Review - The lines of investigation used by

anthropologists to deduce the evolutionary diet of hominids include

the study of: (i) changes in cranio-dental features, (ii) isotopic

chemical tracer methods, including carbon isotope (13C/12C),

strontium isotope (87Sr/86Sr) and trace element Sr/Ca ratios in

enamel and bone of fossils,(iii) comparative gut morphology of modern

humans and other mammals, (iv) the energetic requirements of a

developing a large brain:body size ratio, (v) optimal foraging theory

and food selection, (vi) the study of dietary patterns of surviving

hunter-gatherer societies. Findings show clear cranio-dental changes

including, a decrease in molar teeth size, jaws/skull became more

gracile and front teeth became well-buttressed, all indicative of

less emphasis on grinding course foliage and more on biting and

tearing. Carbon isotope studies indicate the dietary intake of C4

grasses, undoubtedly in the form of herbivorous animals, at a level

which increased substantially during the progression of our genus

from A. aferensis to H. sapiens. Even as far back as 3.5 million

years, the Sr/Ca ratio falls in between those typical for herbivores

and carnivores. Gut morphology studies indicate a closer structural

analogy with carnivores than the folivorous or frugivorous mammals.

Energetic requirements of a relatively enlarged brain have been

balanced by reduction in size and energy requirement of the digestive

system, a phenomena requiring a high quality diet. Investigation of

food procurement habits of hunter-gatherer societies indicates the

advantage of hunting of game animals compared with plant foraging in

terms of energy gain versus expenditure. Study of macronutrient

energy proportions in the diet of HG societies (n=229) show a

relatively high protein intake 19-35%, highly variable fat intake 28-

47% and low carbohydrate level 22-40%. Conclusions - It is postulated

that changes in food staples and food processing procedures

introduced during the Neolithic and Industrial era have fundamentally

altered seven crucial nutritional characteristics of our ancestral

diet: (i) glycaemic load, (ii) fatty acid balance, (iii)

macronutrient balance, (iv) trace nutrient density, (v) acid-base

balance, (vi) sodium-potassium balance, (vii) fiber content.