Vitamin D is produced by the body when it's exposed to sunlight, however inadequate sun exposure can sometimes mean our body's vitamin D levels are low - in fact, nearly one quarter of Australian adults are deficient in vitamin D*. This supplement contains 25 micrograms of vitamin D3, which is retained in the bloodstream more effectively when compared to vitamin D2 (a synthetic form). *Australian Health Survey: Biomedical Results for Nutrients, 2011-12 Supports strong, healthy bones and teeth. Helps increase dietary calcium absorption. Supports muscle health. Maintains a healthy immune system. Naturally derived source of vitamin D3.