Calcium biochemical role, rda and deficiency

Mineral introduction, General functions, Classification, Macroelement of calcium , Ca- introduction, Biochemical role of calcium, recommended dietary allowance of calcium, dietary sources of calcium, Deficiency disease of calcium.

1. Minerals - Introduction The mineral (inorganic) elements constitute only a small proportion of the body weight. There is a wide variation in their body content. For instance, calcium constitutes about 2% of body weight while cobalt about 0.00004%.

2. Minerals – General Functions Minerals perform several vital functions which are absolutely essential for the very existence of the organism. These include: Calcification of bone, Blood coagulation, Neuromuscular irritability, Acid-base equilibrium, Fluid balance and Osmotic regulation.

3. Minerals – General Functions Certain minerals are integral components of biologically important compounds such as hemoglobin (Fe), Thyroxine (I), Insulin (Zn), and Vitamin B12 (Co). Sulfur is present in thiamine, biotin, lipoic acid and coenzyme A. Several minerals participate as cofactors for enzymes in metabolism (e.g. Mg, Mn , Cu, Zn, K). Some elements are essential constituents of certain enzymes (e.g. Co, Mo, Se).

4. Minerals - Classification The minerals are classified as principal elements and trace elements . The seven principal elements ( macroelements ) constitute 60-80% of the body’s inorganic material. These are calcium, potassium, chloride and sulfur. The principal elements are required in amounts greater than 100 mg/day.

5. Minerals - Classification The trace elements (microelements) are required in amounts less than 100 mg/day. They are subdivided into three categories. Essential trace elements: Iron, copper, iodine, manganese, Zinc, molybdenum, cobalt, fluorine, selenium and chromium. Possibly essential trace elements: Nickel, Vanadium, cadmium and barium. Non-essential trace elements: Aluminium , lead, mercury, boron, silver, bismuth.

6. Calcium - Biochemical Role, RDA and Deficiency Diseases Jasmine Juliet .R Biotechnology Department Agricultural college and Research & Institute Madurai.

7. Calcium - Introduction Calcium is the most abundant among the minerals in the body. The total content of calcium in an adult man is about 1 to 1.5kg. As much as 99% of it is present in the bones and teeth. A small fraction (1%) of the calcium bound outside the skeletal tissue , performs a wide variety of functions.

8. Calcium – Biochemical Functions ( i ) Development of bones and teeth: Calcium, along with phosphate, is required for the formation (of Hydroxyapatite ) and physical strength of skeletal tissue I.e. bones and teeth. (ii) Muscle contraction: Ca2+ promotes muscle contraction.

9. Calcium – Biochemical Functions (iii) Blood coagulation: Several reactions in the cascade of blood clotting process are dependent on Ca2+ (factor IV). (iv) Nerve transmission: Ca2+ is necessary for the transmission of nerve impulse.

10. Calcium – Biochemical Functions (V) Membrane integrity and permeability: Ca2+ influences the membrane structure and transport of water and several ions across it. (vi) Activation of enzymes: Ca2+ is needed for the direct activation of enzymes such as lipase (pancreatic), ATPase and succinate dehydrogenase .

11. Calcium – Daily Requirements Adult men and women - 800 mg/day Women during pregnancy,lactation and post-menopause- 1.5 g / day.

12. Calcium - Sources Best sources - Milk and milk products Good sources- Beans, leafy vegetables, fish, cabbage, egg yolk.

13. Calcium – Deficiency Diseases The blood Ca level is maintained within a narrow range by the homeostatic control, most predominantly by Parathyroid hormone. Hence abnormalities in Ca metabolism are mainly associated with alterations in Parathyroid Hormone.

14. Calcium – Deficiency Diseases Hypercalcemia The serum Ca level (normal 9-11 mg/dl) is elevated in hypercalcemia . Hypercalcemia is associated with Hyperparathyroidism caused by increased activity of parathyroid glands. Decrease in serum phosphate (due to increased renal losses) and increase in alkaline phosphatase activity are also found in hyperparathyroidism. Elevation in the urinary excretion of Ca and P, often resulting in the formation of urinary calculi, is also observed in these patients.

15. Calcium – Deficiency Diseases The symptoms of hypercalcemia include: Lethary , Muscle weakness, Loss of appetite, Constipation, Nausea, Increased myocardial contractility and Susceptility to fractures.

16. Calcium – Deficiency Diseases Hypocalcemia Hypocalcemia is a more serious and life threatening condition . It is characterized by a fall in the serum Ca to below 7 mg/dl, causing tetany . The symptoms of tetany include neuromuscular irritability , spasms and convulsions. Hypoparathyroidism is associated with a decrease in serum Ca and an increase in serum phosphate, besides the reduced urinary excretion of both Ca and P.

17. Calcium – Deficiency Diseases Rickets Rickets is a disorder of defective calcification of bones . This may be due to a dietary deficiency of Ca and P or both. The concentration of serum Ca and P may be low or normal. An increase in the activity of Alkaline Phosphatase is a chacteristic feature of rickets.

18. Calcium – Deficiency Diseases Osteoporosis Osteoporosis is characterized by demineralization of bone resulting in the progressive loss of bone mass. Occurrence: The elderly people (over 60 yr) of both sexes are at risk for osteoporosis. However, it more predominantly occurs in the postmenopausal women. Osteoporosis results in frequent bone fractures which are a major cause of disability among the elderly.

19. Calcium – Deficiency Diseases Etiology: The etiology of osteoporosis is largely unknown , but it is believed that several causative factors may contribute to it. The ability to produce calcitriol from Vitamin D is decreased with age, particularly in the postmenopausal women.

20. Calcium – Deficiency Diseases Immobilized or sedendary individuals tend to decrease bone mass while those on regular exercise tend to increase bone mass. Deficiency of sex hormones ( in women) has been implicated in the development of osteoporosis.

21. Calcium – Deficiency Diseases Treatment: Estrogen administration along with calcium supplementation ( in combination with Vitamin D) to postmenopausal women reduces the risk of fractures. Higher dietary intake of Ca (about 1.5 g/day) is recommended for elderly people.