In Vitro Calcium Bioaccessibility In Moringa oleifera Vegetable Leaves: Potential Plant Food To Increase Dietary Calcium Intake In Developing Countries By Issa, Joseph Yohane

Low calcium intake, poor calcium absorption, exessive calcium losses, or some combination of these factors contribute to calcium deficiency diseases. Calcium deficiency can lead osteoporosis, reduced bone mass, hypertension and colon cancer among other diseases.Calcium in bones plays a role in bone mineralization. In other body tissues it plays roles in mediating vascular contraction and vasodilation, muscle contraction, nerve transmission, and glandular secretion.The best food sources of calcium include milk and dairy products, especially cheese and yogurt, and selected seafoods, such as salmon and sardines (with bones), clams, and oysters. Bioavailability and bioaccessibility of calcium is high in milk and dairy products due to the presence of lactose and other factors. However,
calcium bioavailability or bioaccessibility is low in most vegetable plants due to presence of other substances like oxalic acid, phytate and other competing minerals.

Link : http://repository.lib.ncsu.edu/ir/bitstream/1840.16/7742/1/etd.pdf