Bone mass and vitamin D synthesis decrease with aging and inactivity in women and men. Reducing bone loss delays the onset of weakness, thus lowering fracture risk. Peak bone mass is determined by genetics, body weight, weight-bearing activity, and intake of nutrients composing the bone matrix and/or regulating its metabolism. Adequate calcium intake is important to prevent bone resorption and osteoporosis, and higher magnesium intakes have been positively associated with bone mineral density. Vitamin D₃ is essential for maintaining calcium levels and increases calcium absorption from the intestine.