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In the past, attempts have been made to estimate the carbohydrate contents of preagricultural human diets. Those estimations have primarily been based on interpretations of ethnographic data of modern hunter-gatherers. In this study, it was hypothesized that diets of modern hunter-gatherers vary in their carbohydrate content depending on ecoenvironments. Thus, using data of plant-to-animal subsistence ratios, we calculated the carbohydrate intake (percentage of the total energy) in 229 hunter-gatherer diets throughout the world and determined how differences in ecological environments altered carbohydrate intake. We found a wide range of carbohydrate intake (approximate to 3%-50% of the total energy intake; median and mode, 16%-22% of the total energy). Hunter-gatherer diets were characterized by an identical carbohydrate intake (30%-35% of the total energy) over a wide range of latitude intervals (11 degrees-40 degrees north or south of the equator). However, with increasing latitude intervals from 410 to greater than 60 degrees, carbohydrate intake decreased markedly from approximately equal to 20% to 9% or less of the total energy. Hunter-gatherers living in desert and tropical grasslands consumed the most carbohydrates (approximate to 29%-34% of the total energy). Diets of hunter-gatherers living in northern areas (tundra and northern coniferous forest) contained a very low carbohydrate content (<= 15% of the total energy). In conclusion, diets of hunter-gatherers showed substantial variation in their carbohydrate content. Independent of the local environment, however, the range of energy intake from carbohydrates in the diets of most hunter-gatherer societies was markedly different (lower) from the amounts currently recommended for healthy humans. (C) 2011 Elsevier Inc. All rights reserved.