Hunter-gatherer diets in tundra, coniferous forest, temperate grassland, and tropical rainforest ecosystems are net acid-producing, while diets in other ecological niches are neutral or net base-producing, and vegetation density and animal availability jointly constrain dietary acid load.

When people eat mostly meat and few plants, their bodies break down proteins into acids and get fewer alkaline minerals, so their kidneys must remove more acid to keep blood chemistry stable. In places with few plants, people eat more meat and less plant food, so their bodies produce more acid. In places with many plants, people eat more plant food that provides minerals that neutralize acid, so their bodies produce less acid.