Nature's Way Calcium + Vitamin D3 is a premium quality combination supplement of 600mg Calcium and 500IU Vitamin D3 to increase calcium intake and maintain bone strength. A diet deficient in calcium can lead to osteoporosis later in life. Calcium may assist in the prevention of osteoporosis when dietary intake is inadequate. Vitamin D3 is an essential nutrient for the absorption of dietary calcium. Vitamin D3 also supports immune system health and muscle function when sun exposure is inadequate.