Digestion absorbs and metabolizes the energy of food and nutrients
Usually the infant's metabolic rate to body weight is twice that of that of an adult's, which accounts for the fact that cardiac output and respiratory volume per minute are twice that of an adult's body weight
Normally, the digestibility, absorption, and metabolism of infants are not different from those of older children, except for the following 3 characteristics:
1. Newborn’s pancreas does not secrete amylase, so infants often useless starch than older children.
2. Absorption of fat from the gastrointestinal tract is slightly less than in older children. As a result, high-fat dairy, such as cow's milk, is often not fully absorbed.
3. Because the liver function is incomplete at least during the first week, blood sugar levels are unstable and low.
New-borns have a special ability to synthesize and store proteins. In fact, with a complete diet, over 90% of the amino acids ingested will be used to form body proteins, much higher than in adults.
Increased metabolic rate and poor body temperature regulation
Usually, the infant's metabolic rate to body weight is twice that of an adult's, which accounts for the fact that cardiac output and respiratory volume per minute are twice that of an adult's body weight. .
Because the body surface area is large relative to the body weight, it is easily lost from the body. As a result, the body temperature of infants, mainly premature infants, is prone to hypothermia. The figure shows that even a normal baby's body temperature usually drops a few degrees in the first few hours after birth but returns to normal by 7 to 10 hours. However, the mechanisms that regulate body temperature are still poor in the early days, allowing for significant temperature changes, as shown in Fig.
Figure. A decrease in the infant's body temperature immediately after birth and the instability of the body temperature during the first few days of life.
Nutritional needs in the first weeks of the baby
At birth, a child is usually completely nutritionally balanced, if the mother is supplemented with an adequate nutritional diet. Furthermore, the function of the digestive system is usually more able to digest and assimilate the nutrients needed by the infant if the proper nutrients are provided in the diet. However, there are three problems that appear early in the infant's life.
Calcium and Vitamin D requirements
Because infants have a rapid period of ossification at birth, a ready supply of calcium throughout childhood is essential.
Usually provided by milk feeding. However, calcium absorption by the gastrointestinal tract is reduced in the absence of vitamin D. Therefore, within a few weeks, vitamin D deficiency in infants can cause severe rickets. This is especially true in premature infants because their digestive tracts absorb calcium less efficiently than normal infants.
Iron requirements in the diet
If the mother lacks iron in her diet, the baby's liver usually stores enough iron to sustain the formation of blood cells for four to six months after birth. However, if the mother provides iron deficiency in the diet, severe anaemia is likely to occur in the infant after about 3 months. To prevent this possibility, supplementing with egg yolks, which contain reasonable amounts of iron, or using some other form of iron is necessary by the 2nd or 3rd month.
Vitamin C deficiency in infants
Ascorbic acid (vitamin C) is not stored in large quantities in foetal tissues, but it is required for the proper formation of cartilage, bone, and other intercellular structures of the neonate. However, adequate amounts of vitamin C are usually provided by breast milk unless the mother has a severe vitamin C deficiency. Cow's milk contains only 1/4 of the vitamin C content of human milk. In some cases, orange juice or some other source of ascorbic acid is given to infants who are vitamin C deficient.