Calcium is the most abundant mineral in the body. It ensures strength and rigidity of bones. The ends of the long bones are a storehouse of calcium. This reserve can be used during pregnancy, adolescence and lactation when there is an increased need for calcium. When this reserve is not there, calcium is mobilised from the bones. This causes thinning of the bone structure. Those who do not replenish their calcium reserves tend to have thinner bone structure and reduced bone density, leading to osteoporosis.
Calcium is essential to the human body for various reasons. Apart from maintaining the health of the bones and the teeth, it is important for enzyme activity, especially ATP (Adinosine Tri Phosphate). It initiates the process of clotting of blood. It plays an important role in the activity of ions across membranes. It plays a crucial role in nerve transmission and regulating the heartbeat. It also plays a role in muscle activity and muscle tone.
Factors that enhance calcium absorption: Vitamin D in its active form, lactose present in milk and phosphorous aid in calcium absorption. Hydrochloric acid helps calcium absorption by lowering pH. Fat increases the transit time through the digestive tract and the presence of normal protein in the diet helps calcium absorption. Fifteen minutes of exposure to the sun daily has many benefits.
Factors that decrease calcium absorption: Vitamin D deficiency can decrease calcium absorption. Increased fat excretion can also decrease calcium absorption. Oxalates and phytates can make calcium unavailable to the body.
Sources of calcium: Milk and milk products contain calcium. Butter and ghee do not contain calcium. Green leafy vegetables, sea foods and spices contain calcium. In those days, the consumption of chuna with beetle leaf used to be a rich source of calcium. But because of tobacco consumption, the practice has been discouraged. If people can still consume a small amount of betel leaf and chuna without tobacco, it can help increase calcium intake.
Deficiency: Rickets (in children), osteomalacia (demineralisation), osteoporosis (reduction in bone density) and scurvy are associated with calcium deficiency which leads to structural abnormalities in the bone. Tetany (irritability of nerve spasms) and hypertension are related to calcium in the ionised form.
Toxicity: A very high intake of calcium and vitamin D (supplementation) can lead to excessive calcification not only in the bones but also in the soft tissues such as the kidney.
RDA for calcium: Children and adults require about 600 mg per day. During lactation, women require 1200 mg per day. During adolescence and post menopause, the calcium requirement is 800 mg per day.
Dharini Krishnan,Consultant Dietician, Chennai.
