Milk is the opaque liquid food obtained from the mammary glands of animals and is a source of nutrition used by humans. The ingredients of raw milk differ according to the species it is obtained from on the basis of protein, calcium, saturated fat and Vitamin C. Cow’s milk is used extensively as a drink by human beings and used to manufacture many products like chocolates, ice-creams, yogurt, butter etc.
Buttermilk is obtained when the fat has been taken out from the milk to make butter. Buttermilk is considerably lower in calories and fat content but high in calcium, Vitamin B12 and potassium than regular milk. One cup of buttermilk may contain up to 99 calories while milk may contain up to 157 calories. Also, one cup of buttermilk accounts for 2.2 grams of fat while the same amount of milk gives you 9 grams of fat. Buttermilk is also easily digestible than milk.
Milk may also refer to the white non-animal substitutes like rice milk, almond milk, soy milk and coconut milk.
Though milk is considered as an ideal food but in lacks in Vitamin C and iron.
Curd or yogurt is more beneficial than milk.Because of fermentation by Lactobacillus acidophilus,it is rich in whey protein,Vitamin C,Vitamin B complex and natural organic acids( mainly lactic acid). So if you have replaced milk with yogurt it is just great.
Buttermilk is considered beneficial to health as it contains probiotic microbes and is sometimes referred to as "Grandma's probiotic". It is also soothing to stomach and skin.