Milk is the fluid secreted by the female of all mammalian species, primarily to meet the complete nutritional requirements of the neonate, such as energy, essential amino acids and fatty acids, vitamins, minerals and water. Milk is an effective and balanced source of lipids, proteins (caseins and whey proteins), carbohydrates (mainly lactose), minerals (e.g. calcium and phosphate), enzymes, vitamins and trace elements.


Milk from domesticated animals has provided food for humans for more than 8500 years. Milk contains a wide range of readily bio-available nutrients, which enables this nutrient-dense product to be the sole food for neonates and infants during the first stage of growth and development. Moreover, milk and dairy products make a significant contribution to the total supply of nutrients for adolescents and adults. From the early 1900s, public health authorities encouraged the consumption of milk and milk products to improve the nutritional status of the population, especially children.

However, the image of milk and its products was blemished during the past few decades, mainly because they contain saturated fatty acids that can increase the level of serum cholesterol, which is considered as a risk factor for coronary heart disease. More recently, fat in general has been linked to the emerging obesity epidemic and to cancer by some researchers. However, recommendations by public health authorities to limit milk fat intake means that the diet is deprived of several bioactive components that may help prevent disease throughout the life span.

Milk (cow or buffalo or goat milk) may be defined as the whole, fresh, clean, lacteal secretion obtained by complete milking of one or more healthy milch animals, excluding that obtained with in 15 days before or 5 days after calving or such periods as may be necessary to render the milk practically colostrum free and containing the minimum prescribed percentages of milk fat and milk solids not fat (SNF), or simply

MILK is the normal mammary secretion derived from complete milking of healthy milch animal without either addition thereto or extraction therefrom unless otherwise legally warranted and it shall be free colostrum.

The price of milk is usually determined by its fat and / or SNF content.

Milk plasma is defined as milk minus the milk fat globules, which is close in composition to skim milk (or separated milk) although separation of fat from the rest of the milk is never complete. Milk serum is defined as milk plasma minus casein micelles, which is close to the composition of whey, except for the presence of some of the proteolytic products from chymosin.

The composition of different species of milk including human milk or breast milk and chemical composition of milk obtained from different breeds of cows are discussed in Composition of different species of milk

The nutrients present in milk like fat, protein, lactose, vitamins and minerals are explained in Nutrients in Milk

Other constituents of milk such as enzymes, pigments, non protein nitrogenous substances and gases are discussed in other constituents of milk

Learn more about the legal standards for milk and dairy products

Learn more about the goodness of milk and dairy products