Estimation of the diet-dependent net acid load in 229 worldwide historically studied hunter-gatherer societies.

BACKGROUND Nutrition scientists are showing growing interest in the diet patterns of preagricultural (hunter-gatherer) humans. Retrojected preagricultural diets are reportedly predominantly net base producing in contrast to the net acid-producing modern Western diets. OBJECTIVE We examined the dietary net acid load [net endogenous acid production (NEAP)] for 229 worldwide historically studied hunter-gatherer societies to determine how differences in plant-to-animal (P:A) dietary subsistence patterns and differences in the percentage of body fat in prey animals affect the NEAP. DESIGN With the use of 1) ethnographic data of dietary P:A ratios of hunter-gatherer populations, 2) established computational methods, and 3) knowledge that fat densities of animal foods consumed by hunter-gatherers varied between 3% and 20%, we computed the NEAP for the diets of 229 populations in 4 different models of animal fat densities (model A, 3%; model B, 10%; model C, 15%; model D, 20%). RESULTS As P:A ratios decreased from 85:15 to 5:95, the NEAP increased from -178 to +181 mEq/d (model A) and from -185 to +120 mEq/d (models B and C). Approximately 50% of the diets consumed by the 229 worldwide hunter-gatherer populations were net acid producing (models B and C). In model D, 40% of the diets were net acid producing. CONCLUSIONS Our data confirm that the NEAP of hunter-gatherer diets becomes progressively more positive as P:A ratios decline. The high reliance on animal-based foods of a worldwide sample of historically studied hunter-gatherer populations renders their diets net acid producing in approximately 40-60% of subgroups of P:A ratios. Only further investigations can show the implications of these findings in determining the NEAP of human ancestral diets.