In modern hunter-gatherer societies, dietary acid load, as estimated by net endogenous acid production (NEAP), increases with latitude, with diets above 40° to 50° latitude being net acid-producing and diets below this range being net base-producing due to ecological constraints on plant-to-animal food ratios.

In colder regions far from the equator, fewer plants grow, so people eat more meat and less vegetation. Meat breaks down into acids, while plants break down into bases. More meat means more acid in the body, and less plant food means fewer bases to neutralize it. This makes the body more acidic. Near the equator, more plants are available, so people eat more plants and less meat. Plants neutralize acid, so the body stays less acidic.