Calcium: Calcium is a major element in the body and an adult man of 60 kg has nearly 1 kg of calcium, most of which is present in bones. An important function of calcium is the formation of bone. Though small in quantity, non-skeletal calcium has an important role to play in neuromuscular excitation, blood coagulation, membrane permeability and so on. About 20-30% of the calcium in the diet is absorbed and such absorption is greatly facilitated by vitamin D.
The utilization of dietary calcium in human subjects varies from 15 to 20% depending on age and physiological state. Additional calcium is required during growth for skeletal development and during lactation for milk secretion. The daily calcium requirements recommended by (ICMR) Nutrition Expert Group are as follows:
|Pregnancy and lactation
10- 15 years
16- 18 years
Phosphorus: The requirement of phosphorus is closely related to that of calcium. It is generally agreed that phosphorus requirement is about 20% higher than calcium requirement. A large part of the phosphorus present in cereals, pulses and nuts is in the form of phytin. Only a small part of phytin phosphorus is available to the human body. Further, phytin phosphorus interferes with the utilization of dietary calcium and iron. Suggested intakes of phosphorus are as follows:
|Pregnancy and lactation
|Children: 1-9 years
Iron: Iron requirements are computed mainly by the factorial method. Iron lost in urine, sweat and in menstruation in girls is estimated. Iron requirements for growth are calculated from the retention in the body during growth. An average absorption of 10% of food iron is assumed in computing iron requirements.
During early infancy where little change occurs in storage iron and haemoglobin (Hb) levels, a full term infant of 2.7 kg body weight needs only 0.3 mg/day to maintain its Hb at the normal concentration of 11 g/ deci liter and to replace excretory loss. During the second year of life, when growth rate slows down and the body mass increases by 2.5 kg, 80 mg of iron is needed. Added to basal losses, the total requirement during this period is about 0.4mg/ day.
Iron requirements during pregnancy can be calculated from knowledge of iron needs for foetal growth, expansion of maternal tissue including the red cells mass, the content of iron in the placenta and the blood loss during parturition. These additional requirements should be added to the basal requirement.
Iron requirement during lactation is the sum of the requirement of the mother and that required for making up the iron lost in breast milk.
The daily iron requirements recommended by ICMR Nutrition Expert Group are as follows:
|Children: 1-3 years
|Adolescents: 10-12 years