Natural Factors Vitamin D3 is essential for strong bones and teeth as it increases the bodys absorption of calcium from food. Its role in regulating calcium levels also helps regulate the immune system and maintains healthy nerves and muscles.* Natural Factors Vitamin D is an excellent way to support the bodys normal functioning. Suggested Usage: 1 tablet per day or as directed by a health professional. Keep out of reach of children. Contains no artificial preservatives or color; no dairy, wheat or yeast.