Dietary animal protein intake exhibits a non-linear association with bone mineral density in Chinese adults, with a threshold of 0.87 g/kg/day separating beneficial from potentially harmful effects, such that both intakes below and above this threshold are suboptimal for bone health.

When people eat the right amount of animal protein, gut bacteria produce compounds that help the body absorb calcium and keep the blood slightly alkaline, which keeps bones dense. If they eat too little protein, not enough of these compounds are made, so calcium isn't absorbed well and bones weaken. If they eat too much protein, the gut bacteria make too many acidic compounds, which pull calcium out of bones to balance the blood, and bones lose density.