Calcium is the most abundant mineral in our body, about 1.8% of the total weight. Altogether, 99% of the body s calcium is concentrated in dentin, the substance of which bones and teeth are made. Bones not only contain calcium, but they also have a very important deposition function. Calcium is mainly present in bones (98%), to a lesser extent in teeth (1%) and also in body fluids (1%). The main function of calcium in our bodies is related to the formation of bones and teeth, where it plays a structural role in the musculoskeletal system but it also constitutes a primary reserve capable of maintaining the physiological concentration of plasma and supplying a number of metabolic needs.Calcium regulates muscle contraction, intervenes on the transmission of nerve impulses and keeps the nervous system healthy. Calcium also normalises blood circulation and regulates heart rate, lowering blood pressure and cholesterol levels as well as contributing to blood coagulation. Calcium is also involved in cell membrane permeability, cell multiplication and differentiation, the synthesis of certain hormones and the activation of certain enzymes. A truly versatile role, even if it is predominantly associated with the formation of bones.The daily requirement of calcium varies from individual to individual, based on age, sex and physiological conditions. In adults it is 800 mg, in children (up to 10 years) 400-500 mg, in adolescents 1,000-1,300 mg, in the elderly 1,000 mg, in pregnant and nursing women 1,200-1,500 mg. Calcium, together with the synergistic vitamin D, is essential for structuring the skeletal system already in the first months of foetal development, which is why there is an increased need in pregnant women and during breastfeeding. Thereafter, following the peak of skeletal maturity (between 20 and 30 years), the density of calcium in the bones begins to decrease gradually. A calcium deficit in the first years of life can cause problems mainly in bone structure due to reduced mineral density, with the risk of bone deformation and rickets. Insufficient calcium in the diet gives rise to ailments ranging from simple muscle cramps (also in the abdomen) to tingling in the fingers, headaches and memory gaps, irritability and nervousness. Other symptoms include dry skin, brittle nails and hair loss. More severe disorders can affect the osteoarticular apparatus, such as bone pain, fragility and fracture risk, tooth decay, bone decalcification in the elderly and osteoporosis in menopausal women. Excess calcium is eliminated through body secretions: faeces, urine and sweat.People who need to consider calcium supplementation are:those who avoid dairy products (due to allergies or other reasons);menopausal women, who are at risk of osteopenia or osteoporosis;pregnant and lactating women;subjects over the age of 55-60;people suffering from celiac disease or other gastrointestinal problems that can cause malabsorption;those undergoing prolonged treatment with corticosteroids;From childhood, calcium, combined with the complementary support of vitamin D, are fundamental nutrients, widely recommended by the medical profession, for the prevention and treatment of osteopenia, osteoporosis and fractures associated with fragility. Many studies have shown that a low intake, inadequate internal production, or reduced intestinal absorption of these elements is linked to an increased risk of fractures in old age.In addition, calcium and vitamin D are essential for the effectiveness of therapies for osteoporosis.