FACTORS AFFECTING CALCIUM ABSORPTION:
Factors increasing absorption :
1. Vitamin D - induces the synthesis of calbindin (carrier protein for Ca) in the intestinal epithelial cells, thus increasing Ca absorption.
2. Parathyroid hormone - it increases Ca transport across the membrane of intestinal cells.
3 Acidity - Ca is more soluble and absorbed in acidic medium.
4. Lactose - it favors absorption in infants. Lactose is acted upon by intestinal microbial flora to form acid which causes lowering of pH which makes calcium more soluble.
5. Need for calcium - efficiency of calcium absorption increases according to body demands.During pregnancy, lactation and adolescence calcium absorption efficiency increases by 50%.
6. Amino acids - Lysine and arginine increases Ca absorption.
Factors decreasing absorption:
1. Oxalic acid - It is present in vegetables. It combines with Ca to form insoluble complex calcium oxalate which cannot be absorbed.
2. Phytic acid - It is a hexaphosphate of inositol which is present in cereals. Fermentation and cooking reduces the phytate content. It is primarily found in the outer coat of cereals.
3. Malabsorption - eg: steatorrhoea. The fatty acids are not absorbed. This forms insoluble calcium salts of fatty acids.
4. Phosphate - When present in high amount it causes precipitation of calcium in the form of calcium phosphate.
Ideal ratio of Ca: P is 1:2 to 2:1.
5. Laxatives- they decrease the transit time for passage of food through intestinal tract. Thus reducing time for absorption.
6. Caffeine , drugs like anticoagulants, cortisone and thyroxine reduce calcium absorption.
Factors increasing absorption :
1. Vitamin D - induces the synthesis of calbindin (carrier protein for Ca) in the intestinal epithelial cells, thus increasing Ca absorption.
2. Parathyroid hormone - it increases Ca transport across the membrane of intestinal cells.
3 Acidity - Ca is more soluble and absorbed in acidic medium.
4. Lactose - it favors absorption in infants. Lactose is acted upon by intestinal microbial flora to form acid which causes lowering of pH which makes calcium more soluble.
5. Need for calcium - efficiency of calcium absorption increases according to body demands.During pregnancy, lactation and adolescence calcium absorption efficiency increases by 50%.
6. Amino acids - Lysine and arginine increases Ca absorption.
Factors decreasing absorption:
1. Oxalic acid - It is present in vegetables. It combines with Ca to form insoluble complex calcium oxalate which cannot be absorbed.
2. Phytic acid - It is a hexaphosphate of inositol which is present in cereals. Fermentation and cooking reduces the phytate content. It is primarily found in the outer coat of cereals.
3. Malabsorption - eg: steatorrhoea. The fatty acids are not absorbed. This forms insoluble calcium salts of fatty acids.
4. Phosphate - When present in high amount it causes precipitation of calcium in the form of calcium phosphate.
Ideal ratio of Ca: P is 1:2 to 2:1.
5. Laxatives- they decrease the transit time for passage of food through intestinal tract. Thus reducing time for absorption.
6. Caffeine , drugs like anticoagulants, cortisone and thyroxine reduce calcium absorption.
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