Calcium: Clinical Manifestations Of Its Deficiency And Nutritive Importance As A Mineral Supplement
Calcium In Bones
Fourteen elements are absolutely essential for normal body metabolism. These minerals are sodium, potassium, calcium, magnesium, iron, iodine, copper, zinc, cobalt, phosphorus, sulphur, chromium, selenium and fluorine. Though, several other elements are detectable in tissues, their role in nutrition is not clearly understood.
Calcium Rich Foods
The total body content of calcium is 1200g in an adult. This is present in the skeleton, teeth, plasma, and in all tissues. Of the total body calcium, 98% is present in the bones as calcium phosphate (hydroxyapatite) held in a protein matrix (osteoid). Calcium gives the strength and rigidity to the skeleton. In the plasma calcium, is present as the free ions, albumin- bound form and as completes which are diffusible. In health, serum calcium level ranges from 9 to 10.5 mg (2.2 to 3.6 mmol/liter). Calcium and phosphorus levels vary inversely with each other and the product Ca X P is almost constant around 40. The normal function of cell membranes and the electrical activity of excitable tissues like the muscles, nerves and heart depend upon ionized calcium. Calcium ions facilitate the release of acetylcholine from the vesicles in the motor end plates. Coagulation processes require small amounts of calcium.
The main sources of calcium is in diets. Milk, cheese, eggs, meat, peas, beans, certain leafy vegetables, dried fruits and nuts contain good amounts of calcium. Milk protein (Casein) is the richest and most reliable source. One liter of milk contains about 12g of calcium. An egg contains 30 mg of calcium. Drinking water may also contain a variable, but significant amounts of calcium in many areas. Calcium from vegetable foods is not well absorbed since it is present as oxalate. In cereals, calcium is found in the form of phytates which are not absorbed and hence excepting millets, the cereals are poor sources.
Lactating Women Need Calcium
Calcium is absorbed actively from jejunum and passively from the ileum. Intake of vitamin D, acidic pH and presence of proteins in the food favour its absorption. In growing children and pregnant and lactating women, absorption is increased. In older age groups, absorption falls. High fats diet, phytates, oxalates and alkaline pH impair calcium absorption. Normally, 90 to 80% of ingested calcium is lost in feces unabsorbed. In steatorrhea calcium soaps are formed and excess calcium is lost in stool. Calcium is also lost in the urine.
Urinary calcium level depends on the blood levels. Normal adults excrete 300 to 400 mg calcium in 24 hours. Lowering of dietary calcium does not lower urinary calcium correspondingly. As a result, very low calcium intake results in negative balance. Lowering of serum calcium stimulates the secretion of parathyroid hormone which mobilizes calcium from bones. The metabolism of calcium is intimately related to those of vitamin D, parathyroid hormone and clacitonin.
Recommended daily intake is 500 mg for adults, 1200 mg for pregnant and lactating women and 700 mg for adolescents. Hypercalcemia leads to anorexia, nausea, vomiting, constipation, hypotonia, mental depression, lethargy and coma. Persistent hypercalcemia leads to calcification around joints, ligaments, gastric mucosa, cornea and kidneys. Hypercalcemia further depresses the renal function. Hypocalcemia leads to tetany.
© 2014 Funom Theophilus Makama