Normal hair zinc levels of children : Are they affected by drinking-water hardness?

From literature data, a negative correlation was derived between the normal average hair zinc levels of 5-yr-old children and the calcium levels in their drinking water (hair zinc level in mg/kg=-(0.158±0.003) calcium level in mg/L+134;r=0.993,n=6,p=0.0006). Exposure of hair samples of a 5-yr-old child to water with different levels of calcium and zinc did not provide evidence for an exogenous effect of calcium in drinking water on hair zinc levels. Thus, these results support Gibson's hypothesis that calcium in hard drinking water interferes with Zn absorption.