Nutrition and Growth in Infants

Good Nutrition is an integral part of an infant’s growth and development to support the physiological changes that occur during the first year of life.¹

A general indicator of an infant’s optimal growth is consuming an adequate number of calories per day measured as weight for age, length for age and head circumference. In general, most healthy infants double their birth weight by 6 months of age and triple it by 12 months of age. An infant’s growth rate can be assessed by periodically plotting the infant’s weight, length, and head circumference for age and weight for length on World Health Organization (WHO) growth charts throughout the first year of life.¹

Nutrient needs of infants are depending upon the rate of growth, energy expenditure, basal metabolic needs and nutrients consumed. Macronutrients are needed in larger quantities (in gram range); they normally include water, carbohydrates, fat and protein.¹

• Energy
• Protein
• Fats
• Micronutrients
• Iron
• Zinc

Energy

The metabolism of babies and young children differs from that of adults primarily due to rapid physical growth, changes in organ functions and body composition. Accordingly, a baby's daily energy requirements during the first year of life are comparatively high, at around 90 kcal/kg body weight compared to an adult’s 40 kcal/kg.^2,18

• Carbohydrates supply 30% to 60% of the energy intake during infancy. Approximately 40% of the energy in human milk and 40% to 50% of the energy in infant formulas is derived from lactose (The most important carbohydrate in a baby's diet) or other carbohydrates. Lactose helps with the absorption of calcium, which is important to bone development.³
• In normal physiological conditions lactose is hydrolyzed to glucose and galactose by lactase also known as lactase-phlorizin hydrolase, a brush-border membrane-bound enzyme, which is taken up by the intestinal cells and transported into the bloodstream. Lactose which is not hydrolyzed in the small intestine is passed into the colon where it is hydrolyzed by the colonic bacterial enzyme ß-galactosidase resulting in the formation of glucose and galactose. Glucose and galactose are subsequently converted into lactate as well as into the short chain fatty acids (SCFA) acetate, propionate and butyrate. These short chain fatty acids lower the intestinal pH leading to increased mineral absorption of Calcium and Magnesium, hence improves bone mineralization.⁴

Protein

• Protein requirements during the rapid growth of infancy are higher per kilogram of weight than those for adults or older children. For infants it ranges from 1.16g/kg/day for the first 6 months to 1.69g/kg/day for 6 -12 months of age compared to adults 1g/kg/day.¹⁸
• Despite protein quantity, protein quality is one of the vital characteristics of the nutritional value of infant feeding. Human milk that contains predominantly the whey proteins than bovine's milk is the gold standard in early infant nutrition.^5,6 Human milk contains casein to whey in a ratio of 40:60; while in cow’s milk the ratio is 80:20.
• Casein forms clots or curds in the stomach; while whey remains as a liquid and is easier to digest & assimilate providing additional energy & sparing endogenous proteins. As cow’s milk is predominant in casein, its intake results in high curd tension resulting in hard stools and irregular intake of feed by infants.
• Whey is a rich source of Arginine & lysine which may stimulate growth hormone release, stimulating an increase in muscle mass & a decline in body fat.⁶
• Numerous factors affect the quality of proteins; however, the amino acid profile is considered as a major contributor to overall protein quality. Breast-milk proteins assist in providing adequate nutrition to breastfed infants while simultaneously aiding in the defense against infection and facilitating optimal development of important physiologic functions in newborns. Indian Academy of Pediatrics recommends that exclusive breastfeeding should be practiced till the end of six months.¹⁶

Fats

• Up to 98 % of human milk lipids are in the form of triacylglycerols, in which saturated and non-saturated fatty acids are bound to the skeleton of glycerol.
• Palmitic acid, the major saturated fatty acid in human milk, usually represents about 20–25 % of human milk fatty acids. 60% of which is esterified to the sn-2 position in the triacylglycerols (the so-called ß-position).^7-9
• If infants are fed with fats containing mainly palmitic acid located in the sn-2 position, leads to higher absorption and efficiency of palmitic acid in comparison with supplemental milk formulas with triacylglycerols derived from vegetable oils that are predominantly in the sn-1 and sn-3 position.¹⁰
• If palmitic acid is bound in the sn-2 position to glycerol, it does not create compounds with calcium, but is absorbed thereby positively influencing mineralization of the growing skeleton.
• Cow’s milk, as well as plant fats, have lower content of ß- palmitate compared to human milk (cow’s milk only about 40 %, plant oils even only 5–20 %).¹¹
• According to the available data, ß-palmitate positively influences fatty acid metabolism, increases calcium absorption, improves bone matrix quality and the stool consistency, and has a positive effect on the development of the intestinal microbiome.¹⁹

Micronutrients

Calcium, Phosphorus & Vitamin D

• Early childhood is critical for the optimal development of bone matrix mineralization and diet significantly influences this complex process.¹
• Vitamin D deficiency is growing in India among all age groups, and Indian children in general have been reported to consume insufficient calcium. This, in addition to Indian’s changing lifestyle and lack of fortification, led IAP to create a practice guideline for pediatricians in order to prevent and treat vitamin D and calcium deficiency.¹²
• Studies were conducted in the age group of new borns up to 6 months and showed prevalence from 62-95.7%. These studies have revealed predisposition of lower 25(OH)D concentrations to neonatal hypocalcemia and infantile rickets with biochemical evidence of hyperparathyroidism among infants manifesting with hypo-calcemic seizures with Vitamin D deficiency. The Significant association between a deficient Vitamin D status (45.5%) and low birth weight has also been observed.^12,13
• Studies were mainly conducted in the age group of 9 months -5 years with the prevalence of 46-80%.¹⁴
• The calcium content of cow’s milk (120mg per 100ml) is nearly four times that of human milk (34mg per 100ml). Although human milk contains less calcium, it is more easily absorbed than that found in cow’s milk.
• EFSA (2005) states 1.5:1 is optimum Ca:P ratio for infants. A meta -analysis showed average Ca:P ratio in human milk is 1.7:1.22
• Vitamin and mineral supplements should be prescribed only after careful evaluation of the infant's intake. Commercially prepared infant formulas are fortified with all necessary vitamins; therefore formula-fed infants rarely need supplements.¹

Iron

• 82% of Indian children under age of 6-23 months consume less than the recommended amount of Iron and thus the high prevalence of Iron deficiency Anaemia. Only 17.9% of Indian children under age of 6-23 months consume Iron rich food daily.¹⁵
• Iron forms traditionally used in food manufacturing have low bioavailability. Heme (organic) iron, found in meat, and non-heme (inorganic) iron each have a different transporter in the gut. Non-heme iron consists of both ferrous (Fe2+) and ferric (Fe3+) forms, and is the main source of iron compounds used in food fortification.
• Healthy breastfed infants absorb iron well from human milk and usually maintain normal iron stores during the first 4 to 6 months. However, the bioavailability of iron in cow’s milk is much less than human milk. Thus, cow's milk consumption in infancy associated with an increased risk of developing Fe-deficiency anaemia.^{16, 20}
• Formula-fed infants up to 6 months of age should receive iron fortified infant formula, with an iron content of 4 to 8 mg/L. Follow-on formulas should also be iron fortified; however, there is not enough evidence to determine the optimal iron concentration in follow-on formula. ²¹
• In case the above is not possible, Iron supplementation should be advocated.

Zinc

• Zinc is one of the trace elements that can become limiting for exclusively breastfed infants. In contrast to Iron, the requirements are quite high initially (2-3 mg/L) that declines rapidly in the first few months of life and more rapidly around 4 months postpartum.
• Many intervention trials have been conducted in many countries to assess the effect of zinc supplementation on children’s growth, with positive outcomes.
• The EC Directive guidelines recommend a zinc concentration of 300-750 mcg/100 ml formula for term infants.²⁰