Energy source, protein metabolism, and hunter-gatherer subsistence strategies

Abstract

During late winter and spring, hunter-gatherers in temperate, subarctic, and arctic environments often relied on diets that provided marginal or inadequate caloric intakes. During such periods, particularly when stored food supplies dwindled or were used up entirely, lean meat became the principal source of energy. Nutritional problems associated with high-protein, low-energy diets are discussed. These problems include elevated metabolic rates, with correspondingly higher caloric requirements, and deficiencies in essential fatty acids. The relative benefits of adding fat or carbohydrate to a diet of lean meat are evaluated in light of the protein-sparing capacities of these two nutrients. Experimental data indicate that although both enhance high-protein, low-energy diets, carbohydrate is a more effective supplement than fat. Given the nutritional inadequacies of a lean-meat diet, the paper concludes with a discussion of alternative subsistence strategies that increase the availability of carbohydrate or fat at the critical time of year.

The energetic significance of cooking

“…The purpose is not to suggest that protein was more important than fat in human evolution. Indeed, fat-rich portions of animal carcasses, including brain, bone marrow and adipose tissue, would have been actively utilized whenever possible (Stefansson, 1960;Hayden, 1981;Speth and Spielmann, 1983;Defleur et al, 1999). Archaeological evidence suggests that fat derived from bone marrow may have been preferred over muscle tissue as a source of energy and nutrients among early Homo (Blumenschine, 1991;Blumenschine and Madrigal, 1993).…”

“…Archaeological evidence suggests that fat derived from bone marrow may have been preferred over muscle tissue as a source of energy and nutrients among early Homo (Blumenschine, 1991;Blumenschine and Madrigal, 1993). Moreover it is known that diets deriving more than 50% of calories from lean protein can lead to negative energy balance, so-called "rabbit starvation," due to the high metabolic costs of protein digestion (Speth and Spielmann, 1983;Noli and Avery, 1988) as well as a physiological maximum capacity of the liver for urea synthesis (Speth, 1989;Cordain et al, 2000). Rather, we focus on whole meat or animal protein because virtually no research to date has addressed the impacts of cooking on the energy value of fat.…”

The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic

“…The nature of this relationship is virtually identical among all vertebrates (Cordain et al, 2000a) and is exemplified by the cubic polynomial equation in Figure 4. Hunter-gatherers tended to shun very small animals or fat-depleted animals because of their excessive protein content (Noli & Avery, 1988;Speth & Spielmann, 1983;Speth, 1989), and numerous historical and ethnographic accounts have documented the adverse health effects that have occurred when people were forced to rely solely upon the fat depleted lean meat of wild animals (Speth & Spielmann, 1983). Excessive lean protein consumption without adequate fat or carbohydrate causes a condition referred to as 'rabbit starvation' by early American explorers that results in nausea, diarrhea and eventual death (Speth & Spielmann, 1983).…”

“…Hunter-gatherers tended to shun very small animals or fat-depleted animals because of their excessive protein content (Noli & Avery, 1988;Speth & Spielmann, 1983;Speth, 1989), and numerous historical and ethnographic accounts have documented the adverse health effects that have occurred when people were forced to rely solely upon the fat depleted lean meat of wild animals (Speth & Spielmann, 1983). Excessive lean protein consumption without adequate fat or carbohydrate causes a condition referred to as 'rabbit starvation' by early American explorers that results in nausea, diarrhea and eventual death (Speth & Spielmann, 1983). Clinically, this syndrome probably results from the finite ability of the liver to up-regulate the ratelimiting enzymes of urea synthesis, thereby culminating in hyperammonemia and hyperaminoacidemia (Rudman et al, 1973).…”

“…Clinically, this syndrome probably results from the finite ability of the liver to up-regulate the ratelimiting enzymes of urea synthesis, thereby culminating in hyperammonemia and hyperaminoacidemia (Rudman et al, 1973). For a foraging human, the avoidance of the physiologic effects of excessive dietary protein was an important factor in shaping their subsistence strategies (Noli & Avery, 1988;Speth & Spielmann, 1983;Speth, 1989). Lean meat therefore could not be eaten in unlimited quantities, but rather had to be accompanied by sufficient fat or by carbohydrate from plant food sources.…”