Ostelin Vitamin D3 1000IU Liquid provides an easy to consume daily dose of vitamin D3, the form that is produced naturally in the body. Due to lack of sun exposure, many Australians do not achieve sufficient Vitamin D levels. Vitamin D is important as it helps to support muscle function and maintain strong bones. It also promotes calcium absorption, is involved in bone mineralisation and may help maintain a healthy immune system. For pregnant women and the elderly, Vitamin D requirements may increase.