Bio-Organics Calcium 600 + Vitamin D3 400 contains calcium carbonate, the most concentrated form available. This high potency formula combines calcium and vitamin D in doses supported by recent research.  It helps prevent and treat osteoporosis by improving bone density and strength needed to help get the most out of each day. To maximise calcium absorption, a significant quantity of vitamin D3 has been added; a dosage recommended in recent research to reduce bone loss and fracture rates in older people. Together calcium and vitamin D can also help maintain colon health. There is evidence that suggests poor colon health may be associated with reduced calcium and vitamin D absorption and reduced absorption of these nutrients may increase the risk of osteoporosis.