COMPOSITION
Vitamin D, a fat-soluble vitamin that enhances the intestinal absorption of calcium and phosphorus, is essential for the maintenance of a healthy skeleton throughout life. Vitamin D is not naturally present in South African milk and therefore milk is not considered a source of vitamin D. However, 30–40 minutes’ exposure to sunlight every day should provide adequate vitamin D for most people living in South Africa. The best time to be exposed to safe sunlight is before 11:00 or after 15:00 every day. In some regions (e.g. the US and Europe), milk is fortified with vitamin D, hence the reference to vitamin D in some research articles.
Dairy alternatives are generally derived from plant-based ingredients such as soya, rice, almond, oat, coconut, hazelnut or hemp, mixed with water. While they are sometimes used as a replacement for cow’s milk, they are not nutritionally equivalent to milk.
The main difference is that dairy alternatives are low in protein and not a natural source of calcium and vitamin B12. Plant-based drinks are often fortified with calcium and vitamin B12, whereas dairy milk is a natural source of calcium and contains a rich matrix of other micronutrients (including riboflavin (vitamin B 2), vitamin B12, iodine, potassium and phosphorus).
Dairy milk is naturally higher in good-quality protein (about 3.3%) than milk alternatives, which generally contain only around 0.5% protein. (Soy milk is the only plant-based alternative that contains a notable amount of protein, namely 3%.)
Most milk alternatives contain added sugar, whereas plain milk contains only lactose, a type of sugar naturally part of milk.
Rice milk is the lowest in protein and most often fortified with calcium, and vitamins D and B12. Oat milk is higher in carbohydrates and naturally sweet. In general it is a more palatable non-dairy milk options, however, sugar is added and this beverage contains very little protein (less than 1 gram per glass). Almond milk is made out of ground almonds with water. This non-dairy drink is very low in protein with just 1 g per glass) compared to dairy milk’s 8g of protein per glass), but may have more calcium (if fortified) than dairy milk, along with vitamins D and E. Hemp milk is made of hemp seeds, which are high in heart-healthy omega-3 fatty acids. It also has some protein but still far too little and falls short in calcium. Coconut milk has very little protein and is high in fats. It contains about the same amount of saturated fat as whole milk — about 4 grams in a cup. However, the fat in whole dairy milk within its natural matrix differ from the fat in coconut milk and do not have the same health effects
Flavoured milk is a pasteurised and homogenised low-fat dairy milk product that is coloured, sweetened and flavoured. Once bottled, it is sterilised to remove any microorganisms that may have been introduced to the milk during processing. This also give the product an extended shelf life. Flavoured milk usually does not contain more than 2 teaspoons of added sugar per cup.
Raw milk may contain harmful bacteria. By pasteurising milk, which is a simple heat treatment that involves heating milk to 72 °C for 15 seconds, any harmful microorganisms are destroyed. Pasteurisation is an important and well-established food safety measure, which is practiced globally.
Not all milk is pasteurised, but it is illegal to sell raw milk in South Africa for direct use unless the herd or dairy is authorised to do so in terms of the law (R1510). Even then, raw milk should be dealt with cautiously and rather be properly heated prior to use. Note that when milk is heat treated at home it is not necessary to boil the milk; pasteurisation is effective at 72 °C.
Appropriate heat treatment ensures that the food is safe for consumption as it limits harmful bacteria that may be present in food. Milk can be heat treated in four ways:
- Pasteurisation: Milk is heated to 72 °C for 15 seconds, then rapidly cooled to 4 °C.
- Ultra-pasteurisation: This involves treatment at a higher temperature and a shelf-life of more than 14 days can be achieved if the milk is kept at 4 °C or lower (Such products are often labelled ESL, for extended shelf-life).
- Ultra-high temperature treatment (UHT): Milk is heated to 135–150 °C for 2–4 seconds and then cooled to 4 °C or lower. This treatment is used to produce long-life milk.
- Sterilisation: This involves heating bottled milk to 110–130 °C for 10–30 minutes, after which the bottles are cooled. Unopened bottles of sterilised milk keep for a long time without the need for refrigeration.
Fortified milk is milk that has been enriched with specific nutrients. The nutrients that are added (e.g. folic acid, vitamin D, iron or protein) are often based on insufficiencies seen in specific consumer categories, such as women of reproduction age, young children and the elderly.
Organic farming avoids the use of soluble fertilisers, pesticides, feed additives and other chemicals. The nutritional composition of milk is largely related to the pasture on which cows graze and organic farming therefore makes a fairly small nutritional difference to milk. Organic milk usually contains higher amounts of omega-3 fatty acids, although the absolute amount is still quite low. Therefore, this may have little effect in the context of an individual’s overall diet. Organic milk also contains about a third less iodine than regular milk. Iodine is important for cognitive function and is therefore particularly important for pregnant women.
Raw milk is milk that has not been (e.g. pasteurised, sterilised or subjected to ultra-high temperature treatment). Drinking raw milk is generally considered to be risky as it may contain harmful bacteria, which would normally be destroyed during pasteurised milk.