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Essential Nutrients in children

Essential Nutrients are the active principles in diet, each with various functions and metabolic patterns. Essential Nutrients may be classified as —

a) Macro nutrients or proximate principles like proteins, fats and carbohydrates.

b) Micro-nutrients like Vitamins and minerals.

Proteins, which constitute —20% of body weight, are important source of energy, as well as required for body building i.e. growth of muscles and various tissues, repair and maintenance of tissues, synthesis of substances like antibodies, plasma proteins, enzymes, hormones, hemoglobin, clotting factors etc., maintenance of osmotic pressure in various tissue compartments.

Biochemistry: Proteins are complex nitrogenous compounds made up of smaller units i.e. amino acids. While some amino acids can be synthesized in body, others cannot, and have to be essentially supplied from diet (essential amino acids). In general, there are 8 Essential Nutrients in the form of amino acids — methionine, threonine, tryptophan, valine, isoleucine, leucine, phenylalanine and lysine (acronym-MeTTVILPLy). Some other amino acids are essential only in infants (histidine) or in low birth weight babies (arginine, cysteine and taurine).

Essential Nutrients Requirements: While precise RDA for proteins in various age groups is given in, in practice, it is easier to calculate protein requirements in healthy children according to their weight.

Protein requirements are relatively higher in PEM and during recovery from illnesses/infections, due to endogenous protein breakdown in muscles & liver to provide essential amino acids.

Sources of Essential Nutrients

Dietary proteins are provided from animal sources like milk, meat, egg, fish etc. as well as vegetable sources like cereals, pulses, beans and nuts. Quality of proteins from various source differ, depending on their digestibility, biological value (% of absorbed proteins retained in the body) and net protein utilization or NPU (% of ingested proteins, retained in the body).

Animal proteins have more Essential Nutrients than vegetable proteins. Egg is considered as a reference protein because of its high biological value, digestibility and NPU (96). NPU of other animal proteins is also relatively higher (cow’s milk—85, meat-76, fish-74) than that of vegetable proteins (rice-77, wheat-61). Soya bean is the richest source of vegetable protein but with lower NPU due to poor digestibility.

Vegetable proteins also lack in certain essential amino acids, termed as ‘limiting amino acids’. Cereal proteins are deficient in lysine and threonine, while pulses are deficient in methionine. Deficiency of these limiting amino acids in vegetarian diet may be corrected by using combination of cereals and pulses.

Fats are the major source of Essential Nutrients (adipose tissue or brown fat) as well as also required as a vehicle for fat-soluble vitamins, as a source of essential fatty acids, for temperature regulation and to increase palatability of food. Being the most concentrated source of energy (9 cal/kg), fats are commonly used to increase the caloric content of food without increasing its bulk.

Biochemistry of Essential Nutrients: Fats are classified as – simple fats like triglycerides, derived lipids like cholesterol, and compound lipids like phospholipids. Over 95% of dietary lipids and —99% of stored lipids in diet are triglycerides. Fats yield to fatty acids and glycerol on hydrolysis.

Fatty acids may be classified as saturated fatty acids like palmitic or stearic acid, monounsaturated fatty acids like oleic acid, and polyunsaturated fatty acids (PUFA) like linoleic acid, linolenic acid or arachidonic acid. Of these, PUPA cannot be adequately synthesized in body and have to be derived from ingested food, thus also termed as Essential fatty acids (EPA).

EPA are essential nutrients for — a) normal growth and brain development, b) structural integrity of cell membrane and c) inflammatory response to produce various mediators like prostaglandins. EFA deficiency has been linked with phrynoderma (dry skin), growth failure, developmental retardation, reproductive failure and increased susceptibility for infections.

Circulatory lipids usually exist in bound-form with proteins (Lipoproteins) like chylomicrons, high-density lipoproteins (HDL), low-density lipoproteins (LDL) and very low-density lipoproteins (VLDL). HDL has lower fat and higher protein content than LDL and VLDL.

Essential Nutrients: Total and saturated fat intake should not exceed 20% and 10% of total caloric intake per day, respectively. In addition, Minimum 2-3% of caloric requirements should be derived from EFAs and 0.3% from linolenic acid.

Sources of Essential Nutrients

Dietary fats are derived from either a visible source like animal fats (ghee, vegetable oils) or invisible sources (cereals and pulses). In Indian diet, >50% of fat is consumed as invisible fat.

Animal fats mainly contain saturated fatty acids and are poor source of EFA. Breast milk has enough EFAs to meet the baby’s requirements. All vegetable oils, except palm oil & coconut oil, are rich sources of EFA.

Coconut oil is a rich source of Essential Nutrients, medium chain triglycerides (MCT) – the only fat that does not require bile for absorption and directly absorbed into the portal vein. Hence, it is often used in malabsorption states, chronic hepatic disease and low birth weight newborns as a human milk fortifier.

Carbohydrates are most important source of ready as well as stored energy, as well as also essential for oxidation of fats and synthesis of certain non-EFA5.

Biochemistry: Carbohydrates are consumed either as free-sugars like monosaccharides (glucose, fructose and galactose) and disaccharides (sucrose, maltose, lactose) or as complex-sugars i.e. polysaccharides like starch, cellulose, dextrin etc. However, all types of carbohydrates are finally converted into glucose for use as metabolic fuel.

Normal glucose homeostasis is maintained by three important metabolic pathways Glycogenesis i.e. conversion of free glucose and fat into glycogen for storage in liver & muscles, Glycogenolysis i.e. endogenous breakdown of hepatic/muscle glycogen to provide free glucose in starvation conditions, and Neogluco genesis i.e. conversion of endogenous or dietary proteins and glycerol into Glucose, in starvation states. Unlike hepatic glycogenolysis, glycogenolysis in muscles is an anaerobic process with production of lactic acidosis, responsible for starvation ketoacidosis.

Requirements: Carbohydrates should provide minimum 50-60% of caloric intake, preferably as complex-sugars to minimize post-prandial blood glucose fluctuations.

Sources: Starch is the commonest carbohydrate in diet, present in grains, legumes and tubers. Glycogen is present only in animal sources.

Fibers are complex carbohydrates like cellulose, hemi cellulose, gums, pectins, and mucilages etc., present in plant cell walls. Although of no caloric value due to their non-digestibility, presence of adequate fibers in diet is essential for colonic water absorption and softening of stools. While vegetarian diet contains adequate fibers, low-fiber non-vegetarian diet has been linked with higher risk of constipation, colonic cancers and hypercholesterolemia.

Vitamins are non-energy-yielding organic compounds, which act as co-factors in many enzyme systems to catalyze cellular metabolism. Although required in miniscule amounts, vitamins are essential for normal growth and maintenance of various body functions.

Vitamins may be divided into two groups i .e.fat-soluble vitamins like Vitamin A, D, E, K and water-soluble vitamins like those of B-complex group and Vitamin C. Of these, Vitamin D and K is also synthesized in body (endogenous source).

Vitamin-related abnormalities may be broadly divided into — a) deficiency disorders, b) hypervitaminosis or excess states, and c) dependency states i.e. inherited errors in metabolic/enzyme activity, dependent on related vitamins.

Minerals are non-energy yielding inorganic compounds, which contribute to —3-4% of body weight and mainly present in bones (—80%), muscles (—10%) and body fluids (—4%). Biologically important minerals are classified as —

a) Macro-minerals, which are present in substantial amounts and their Essential Nutrients usually exceeds >100 mg/day. Although some of these minerals are concentrated in tissues like bones and muscles (like Ca, Mg, P), most of them are major electrolytes in body fluids as cations — Nat, Kt Ca’ Mg or anions — P, CL.

b) Micro-minerals (trace elements), which constitute less than 250 pig/gm of body tissue matrix like iron, iodine, zinc, fluorine etc. Minerals present in still smaller amounts (<100 ng/gm of matrix) are termed as ultra-trace elements. Despite miniscule requirements, trace elements play significant role in human health and disease.

ESSENTIAL NUTRIENTS

Nutrients are the active principles in diet, each with various functions and metabolic patterns. These may be classified as —

a) Macronutrients or proximate principles like proteins, fats and carbohydrates.

b) Micronutrients like Vitamins and minerals.

Proteins, which constitute —20% of body weight, are important source of energy, as well as required for — a) body building i.e. growth of muscles and various tissues, b) repair and maintenance of tissues c) synthesis of substances like antibodies, plasma proteins, enzymes, hormones, hemoglobin, clotting factors etc.d) maintenance of osmotic pressure in various tissue compartments.

Biochemistry: Proteins are complex nitrogenous compounds made up of smaller units i.e. amino acids. While some amino acids can be synthesized in body, others cannot, and have to be essentially supplied from diet (essential amino acids). In general, there are eight essential amino acids — methionine, threonine, tryptophan, valine, isoleucine, leucine, phenylalanine and lysine (acronym-MeTTVILPLy). Some other amino acids are essential only in infants (histidine) or in low birth weight babies (arginine, cysteine and taurine).

Requirements: While precise RDA for proteins in various age groups is given in Table 5.1, in practice, it is easier to calculate protein requirements in healthy children according to their weight (Table 5.3).

Protein requirements are relatively higher in PEM and during recovery from illnesses/infections, due to endogenous protein breakdown in muscles & liver to provide essential amino acids.

Sources: Dietary proteins are provided from animal sources like milk, meat, egg, fish etc. as well as vegetable sources like cereals, pulses, beans and nuts. Quality of proteins from various source differ, depending on their digestibility, biological value (% of absorbed proteins retained in the body) and net protein utilization or NPU (% of ingested proteins, retained in the body).

Animal proteins are nutritionally superior to vegetable proteins. Egg is considered as a reference protein because of its high biological value, digestibility and NPU (96). NPU of other animal proteins is also relatively higher (cow’s milk—85, meat-76, fish-74) than that of vegetable proteins (rice-77, wheat-61). Soya bean is the richest source of vegetable protein but with lower NPU due to poor digestibility.

Vegetable proteins also lack in certain essential amino acids, termed as ‘limiting amino acids’. Cereal proteins are deficient in lysine and threonine, while pulses are deficient in methionine. Deficiency of these limiting amino acids in vegetarian diet may be corrected by using combination of cereals and pulses.

Fats are the major source of stored energy (adipose tissue or brown fat) as well as also required — a) as a vehicle for fat-soluble vitamins, b) as a source of essential fatty acids c) for temperature regulation and d) to increase palatability of food. Being the most concentrated source of energy (9 cal/kg), fats are commonly used to increase the caloric content of food without increasing its bulk.

Biochemistry: Fats are classified as – simple fats like triglycerides, derived lipids like cholesterol, and compound lipids like phospholipids. Over 95% of dietary lipids and —99% of stored lipids in diet are triglycerides. Fats yield to fatty acids and glycerol on hydrolysis.

Fatty acids may be classified as saturated fatty acids like palmitic or stearic acid, monounsaturated fatty acids like oleic acid, and polyunsaturated fatty acids (PUFA) like linoleic acid, linolenic acid or arachidonic acid. Of these, PUPA cannot be adequately synthesized in body and have to be derived from ingested food, thus also termed as Essential fatty acids (EPA).

EPA are essential for — a) normal growth and brain development, b) structural integrity of cell membrane and c) inflammatory response to produce various mediators like prostaglandins. EFA deficiency has been linked with phrynoderma (dry skin), growth failure, developmental retardation, reproductive failure and increased susceptibility for infections.

Circulatory lipids usually exist in bound-form with proteins (Lipoproteins) like chylomicrons, high-density lipoproteins (HDL), low-density lipoproteins (LDL) and very low-density lipoproteins (VLDL). HDL has lower fat and higher protein content than LDL and VLDL.

Requirement: Total and saturated fat intake should not exceed 20% and 10% of total caloric intake per day, respectively. In addition, Minimum 2-3% of caloric requirements should be derived from EFAs and 0.3% from linolenic acid.

Sources: Dietary fats are derived from either a visible source like animal fats (ghee, vegetable oils) or invisible sources (cereals and pulses). In Indian diet, >50% of fat is consumed as invisible fat.

Animal fats mainly contain saturated fatty acids and are poor source of EFA. Breast milk has enough EFAs to meet the baby’s requirements. All vegetable oils, except palm oil & coconut oil, are rich sources of EFA.

Coconut oil is a rich source of medium chain triglycerides (MCT) – the only fat that does not require bile for absorption and directly absorbed into the portal vein. Hence, it is often used in malahsorption states, chronic hepatic disease and low birth weight newborns as a human milk fortifier.

Carbohydrates are most important source of ready as well as stored energy, as well as also essential for oxidation of fats and synthesis of certain non-EFA5.

Biochemistry: Carbohydrates are consumed either as free-sugars like monosaccharides (glucose, fructose and galactose) and disaccharides (sucrose, maltose, lactose) or as complex-sugars i.e. polysaccharides like starch, cellulose, dextrin etc. However, all types of carbohydrates are finally converted into glucose for use as metabolic fuel.

Normal glucose homeostasis is maintained by three important metabolic pathways — a) Glycogenesis i.e. conversion of free glucose and fat into glycogen for storage in liver & muscles, b) Glycogenolysis i.e. endogenous breakdown of hepatic/muscle glycogen to provide free glucose in starvation conditions, and c) Neogluco genesis i.e. conversion of endogenous or dietary proteins and glycerol into Glucose, in starvation states. Unlike hepatic glycogenolysis, glycogenolysis in muscles is an anaerobic process with production of lactic acidosis, responsible for starvation ketoacidosis.

Requirements: Carbohydrates should provide minimum 50-60% of caloric intake, preferably as complex-sugars to minimize post-prandial blood glucose fluctuations.

Sources: Starch is the commonest carbohydrate in diet, present in grains, legumes and tubers. Glycogen is present only in animal sources.

Fibers are complex carbohydrates like cellulose, hemi cellulose, gums, pectins, and mucilages etc., present in plant cell walls. Although of no caloric value due to their non-digestibility, presence of adequate fibers in diet is essential for colonic water absorption and softening of stools. While vegetarian diet contains adequate fibers, low-fiber non-vegetarian diet has been linked with higher risk of constipation, colonic cancers and hypercholesterolemia.

Vitamins are non-energy-yielding organic compounds, which act as co-factors in many enzyme systems to catalyze cellular metabolism. Although required in miniscule amounts, vitamins are essential for normal growth and maintenance of various body functions.

Vitamins may be divided into two groups i .e.fat-soluble vitamins like Vitamin A, D, E, K and water-soluble vitamins like those of B-complex group and Vitamin C. Of these, Vitamin D and K is also synthesized in body (endogenous source).

Vitamin-related abnormalities may be broadly divided into — a) deficiency disorders, b) hypervitaminosis or excess states, and c) dependency states i.e. inherited errors in metabolic/enzyme activity, dependent on related vitamins.

Minerals are non-energy yielding inorganic compounds, which contribute to —3-4% of body weight and mainly present in bones (—80%), muscles (—10%) and body fluids (—4%). Biologically important minerals are classified as —

a) Macro-minerals, which are present in substantial amounts and their nutritional requirement usually exceeds >100 mg/day. Although some of these minerals are concentrated in tissues like bones and muscles (like Ca, Mg, P), most of them are major electrolytes in body fluids as cations — Nat, Kt Ca’ Mg or anions — P, CL.

b) Micro-minerals (trace elements), which constitute less than 250 pig/gm of body tissue matrix like iron, iodine, zinc, fluorine etc. Minerals present in still smaller amounts (<100 ng/gm of matrix) are termed as ultra-trace elements. Despite miniscule requirements, trace elements play significant role in human health and disease.

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