CARBOHYDRATES
Lactose, the main carbohydrate in milk, is produced in a cow’s mammary glands. It is a disaccharide composed of galactose and glucose. Lactose accounts for approximately half of the total 8.9% non-fat solids of milk and contributes about 30% of the energy of full-cream milk. Cow’s milk contains about 4.8% lactose, which translates to 12 g lactose per 250 mL.
Lactose intolerance is not an allergy but rather is a digestive problem which occurs when someone does not have sufficient levels of the enzyme lactase to digest lactose. If not digested in the small intestine, lactose (the natural milk sugar) reaches the colon unchanged. Here, bacteria that occur naturally in the colon then ferments the undigested lactose.
This fermentation process may lead to the formation of acid and gas, while the body may simultaneously attempt to dilute the concentration of the lactose by re-absorbing water from the blood. This can cause diarrhoea. Intakes of more than 12 g lactose (typically one glass of milk or 250 mL) may lead to symptoms such as abdominal pain, discomfort, bloatedness, flatulence, cramping and diarrhoea.
Consuming small quantities of milk (typically half a cup of milk*) with other foods (e.g. cereal), as well eating naturally fermented dairy products such as yoghurt or maas, is recommended for someone who is lactose intolerant. Hard cheeses like Cheddar and Gouda contain virtually no lactose and should not have any adverse effect.
*Half a cup of milk = 6 g of lactose
Milk naturally contains a type of sugar called lactose (approximately 4.8 g per 100 mL). No sugar is added to fresh or long-life plain milk. However, flavoured milk or milkshakes contain added sugars (usually not more than 2 teaspoons per 250 mL serving). This will be specified on the label. The World Health Organization recommends restricting added or free sugars in food. Free sugars are generally defined as ‘all monosaccharides and disaccharides added to foods by the manufacturer, cook or consumer, plus sugars naturally present in honey, syrups and unsweetened fruit juices’. Although the sugar naturally present in milk (lactose) does not fall in this category, it must be declared as ‘sugar’ on the nutrition information label
Before discussing how much lactose is present in milk, it is important to point out that according to law, all milk must have 3% protein/100 ml. The fat varies according to the prescribed fat classes. When the milk arrives at the dairy, all milk offered for human consumption is processed and the cream is skimmed through a process called ‘centrifugation’ after which the milk is homogenised, heat treated and packed according to the specific standards. During packaging, the acquired percentage of fat is then added back.
The fat percentages in milk according to regulations are:
> 3.3%—4.5% for full-cream
> 1.5%-3.3% for medium-fat
> 0.5%-1.5% for low-fat
< 0.5% for fat-free.3
This means that if protein and fat are standardised, the only potential variant is the carbohydrate (lactose) portion. Due to the slight change in volume of milk versus fat, there is a negligible increase in lactose in low-fat or fat-free milk versus full-cream milk. In other words, low-fat and fat-free milk by proportion have more ‘milk’ due to their lower fat content and therefore may have fractional amounts more lactose. No additional sugar is ever added to fresh pasteurised or UHT, low-fat or fat-free milk. If in doubt, a good place to look is on the list of ingredients. If there is no sugar on the ingredients list, it means that no sugar has been added to the milk.
No. The carbohydrates (i.e. sugar) listed as part of the nutrition information come from lactose, a type of sugar naturally found in milk. All types of plain milk (i.e. fat-free, low-fat and full-cream milk) have approximately 4.8% lactose. This works out to about 12 g per cup (250 mL).