Ocean Health Vitamin D3 1000IU is in the form of cholecalciferol, a potent and convenient once a day supplement. Vitamin D is essential in developing and maintaining strong bones, teeth and muscle through increasing calcium and phosphorus absorption in the body. As sunlight is required to produce Vitamin D in human skin, people with limited sunlight exposure due to work, lifestyle or health concerns would have an increased need for Vitamin D supplementation. Vitamin D supplement should be taken by those who are prone to Vitamin D deficiency and elderly to promote healthy bones and strong immune system.