Macro-nutrients in milk
Foods provide us with energy in the form of calories (Kcal).
Calories effectively act as the fuel that powers our bodies and enables us to function, in the same way that petrol fuels a car.
The calorie/energy content of milk varies depending on the fat content. For example, whole standardised milk (3.5% milk fat) provides 68kcals per 100ml; semi-skimmed milk (1.7% milk fat) provides 47kcals/100ml and skimmed milk (0.3% milk fat) provides 35kcals /100ml.
Milk can be described as “nutrient dense” relative to its energy content as it is such a good source of many vitamins and minerals.
Higher calorie milks are more suitable for those who have increased energy requirements e.g. children and adolescents, or those with poor appetites who need nutrient dense foods to provide as many calories as possible in small amounts e.g. the elderly.
Lower calorie milks are suitable for the majority of the population and are especially useful when consumed as part of a calorie controlled diet for contributing to weight loss.
N.B. semi skimmed and skimmed milks are not recommended for children under 2 years of age.
Protein is essential for growth and repair of tissues and for the production of hormones and enzymes which are essential to the correct functioning of the body.
Milk is a source of “high biological value” protein - which means that it provides us with all the essential amino acids that the body cannot make itself.
Milk contains approximately 3.5% protein by weight which can be divided into two main groups: caseins and whey proteins.
Approximately 80% of the protein in milk is casein based and 20% is whey based.
Casein is the predominant protein in milk and can be divided into four major types: alpha, beta, gamma and kappa caseins.
Whey protein comprises the rest of the milk protein and is composed predominantly of beta -lactoglobulin and alpha-lactalbumin.
But other whey proteins include serum albumin, immunoglobulins (IgA, IgG, IgM), protease peptones, lactoferrin and transferrin.
Carbohydrates provide the body with energy required for most functions in the body.
The form of carbohydrate found in milk is known as lactose and is the least damaging sugar with regards to tooth decay. For this reason, plain milk and water are the only 2 drinks recommended by dentists to be safe to consume between meals.
There is approximately 9.7g of lactose in 1 glass/200ml of semi skimmed milk.
Plain milks contain no added sugar, but flavoured milks may contain varying amounts of added sugar depending on the product.
Flavoured milks are therefore not recommended for consumption between meals however they still contain all the same nutrients as plain milks and are a great alternative to fizzy and sugary soft drinks.
Fat is required for many functions in the body including storage and provision of energy, production of hormones, protection, warmth and provision of fat soluble vitamins amongst many others.
The fat in milk contributes unique characteristics to the flavour, texture, appearance and satiability of dairy foods as well as providing a source of fat soluble vitamins, essential fatty acids and other health promoting compounds.
The fat present in milk exists as small globules throughout the milk. The fat globules are less dense than water and rise to the top forming a cream layer. The process of “homogenisation” stops this occurring as the fat globules are broken up into smaller globules and therefore do not rise to the top.
The fat content of milk varies depending on the product e.g. whole standardised milk has a minimum fat content of 3.5g/100ml or 3.5% fat, semi skimmed milk contains 1.7g/100ml or 1.7% fat, 1% fat milk contains 1g/100ml and skimmed milk contains 0.3g/100ml or 0.3% fat.
Fats are made from a range of different fatty acids and the composition of the fatty acids in milk varies depending on the breed of cow from which it was produced, the feed given to the cow, the geographical location, the season and the stage of lactation.
About one third of the fat in milk is monounsaturated - the same type of fat that olive oil contains.
The remainder is mostly saturated, but some polyunsaturated fats and other minor fatty acids are also present.
Saturated fatty acids are usually associated with increased risk of cardiovascular disease through their cholesterol raising effects; however studies have indicated that this does not apply to all saturated fatty acids in milk. In fact some of the saturated fatty acids in milk may reduce the cholesterol raising effects of other saturated fatty acids. Some are even associated with a direct cholesterol lowering effect which is linked with reducing the risk of cardiovascular disease.
Studies have also identified other fats in milk such as Conjugated Linoleic Acid (CLA) - a Trans fat - which may potentially protect against several major chronic illnesses.