Introduction
Milk is the only product which is considered nature's almost perfect food. It is treasure house of unlimited nutrients. Milk is an almost ideal food. It supplies body-building proteins, bone-forming minerals and health-giving vitamins and furnishes energy-giving lactose and milk fat.They are not only of higher quality but are present in milk in such form and proportion that their digestion and assimilation in the body is very efficient.If it is included in our diet it enhance digestion and assimilation of nutrients of other food products.Milk has long been recognized as the most wholesome and complete single food available in nature for health and as a medicine, both preventive as well as curative.
Nutritional Quality of Milk Proteins
Milk proteins are said to be of 'high biological value' as they contain all essential amino acids in amounts and proportions required to support growth and perform numerous function within the body. Protein contribute to building and repair of body tissue, participating in muscular contraction, acting as antibodies, as body's immunological defense mechanism and supplying energy.Casein make up approximately 80% of milk proteins, the remaining being whey proteins.Whey proteins especially are of higher nutritional quality, containing 51% essential amino acids, as compared to 45% in casein.The protein efficiency ratio(3.1), Biological Value(91), and Net protein utilization (82) of milk protein are very close to that of egg proteins (3.8,100 and 94, respectively).
Whey protein contains the highest concentration of branched chain amino acid(BCAA) of any single protein source. The BCAA content is important to athletes because BCAAs are integral part of muscle metabolism and are the first amines sacrificed during intense exercise and muscle catabolism.
The digestibility of milk proteins is rated higher(96%) than that of plant proteins (74-78%).
Nutritional Benefits of Milk Fat
Compared to other fats and oils, milk fat is easily digestible.The digestibility of milk fat is 99%, while that of natural palm oil 91%. The excellent digestibility of milk fat is due to dispersion of fat globules in the aqueous phase of milk forming an emulsion. Also, milk fat is rich in short and medium chain fatty acids. The ester bonds involving short chain fatty acids are more easily cleaved by lipases. Of the fatty acids 62% is saturated (mainly butyric, caproic, myristic, palmitic, stearic acid) and 37% unsaturated`(mainly oleic acid). In the unsaturated fatty acids, 3.8% is PUFA (2.1% linoleic acid, 0.5% linolenic acid). Milk fat has a low content of essential fatty acids(EFA), linoleic and linolenic. Mother's milk contains relatively higher EFA content than cow or buffalo milk.Milk fat imparts a soft body, smooth texture and rich taste to dairy products.
Nutritional Benefits of Lactose
The principal function of lactose(carbohydrate) is to supply energy. However, lactose also helps to establish a mildly acidic reaction in the intestine( which checks the growth of proteolytic bacteria) and facilitates assimilation.
Nutritional Benefits of Minerals
Milk is an excellent source of calcium and phosphorus(two major bone-building minerals), both of which, together with Vitamin D, are essential for bone formation. Milk rather low in iron, copper, iodine and magnesium.The calcium in milk is well utilized in human body. A 250 ml serving of cow milk contains calcium equivalent to 60% of ICMR's recommended Dietary Allowance(RDA) for adults and equal amount of buffalo milk contains 95% of calcium RDA for adults.
Milk is rich in phosphorus that reduce urinary calcium excretion and counter balance, at least in part, the calciuric effect of dietary proteins.The calcium content of human milk is considerably lower than that of cow milk, but calcium from human milk is better utilized by infants(higher calcium to phosphorus ratio).
Nutritional Benefits of Vitamins
Milk is a good source of Vitamin A(provided the cow is fed sufficient green feed and fodder), vitamin D (provided the cow is expected to enough sunlight), Thiamine(for normal appetite and digestion), riboflavin (helps in oxygen uptake and adapting eye to light). However, milk is deficient in vitamin C. Daily Intake of 280 ml of milk supplies adequate quantities of fat soluble vitamin.Milk also contains vitamin K and E.
Energy value of milk constituent
Milk Fat 9.3 C/g
Milk Protein 4.1 C/g
Milk Sugar 4.1 C/g
where 1 C(food calories) = 1000 c(small calories).
Note: The energy value of milk will vary with its composition. On average cow milk furnishes 75 C/100 g and buffalo milk 100 C/100 g.
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