Fig. 3. Interaction between calcium and past smoking exposure (y*pack) on total body bone mineral density. Values, mean ± SE (g/cm2), are adjusted for below and above median of calcium intake (750 mg/day), never-smokers and past smokers, and all other confounders. Note the negative effect of past smoke exposure in the <750 mg/day Ca group and no effect in the >750 mg/day Ca group.