Blackmores Bio Calcium contains calcium to aid in the formation and maintenance of bones, and vitamin D to improve calcium absorption and help calcium stay in the body. Blackmores only uses natural vitamin D3. Ageing can significantly decrease the skin’s capacity to produce vitamin D3. Blackmores Bio Calcium may be particularly beneficial for women, and for people whose consumption of dairy products is low. Calcium is the most abundant mineral in the body, and approximately 99% of the body’s calcium exists in the bones. The major function of calcium is building and maintaining bones and teeth.