MILK, OTHER DAIRY FOODS AND BLOOD GLUCOSE

People have been consuming milk as part of their diet since prehistoric times. Unsurprisingly, cow milk is the most-consumed milk worldwide because of its widespread availability and large production volumes. However, non-cow milks are of nutritional importance to people in developing countries as well as in geographical areas in which the natural climate is unsuitable for the survival of dairy cattle. For example, buffalo milk in Asia, sheep milk in Europe and the Mediterranean basin, camel milk in Africa, goat milk in Africa and southern Asia, horse milk in the steppe areas of central Asia, yak milk on the Tibetan plateau, reindeer milk in northern Scandinavia, musk ox milk in the Arctic, and mithun milk in the hilly regions of the Indian subcontinent.

As can be seen from the table, below, the milk from different species vary in nutrient composition. Protein, fat, carbohydrate (the sugar lactose), and minerals (ash) are the four major components in all milks, irrespective of the species. Of course, the composition of milk varies considerably within the same species because of various factors, such as breed, stage of lactation, milking interval, type of feed/food, and climate.

As can be seen from the table, all mammalian milks contain lactose as it is a vital fuel source for rapidly growing brains and nervous systems, regardless of the species. Human milk contains more lactose and lactose-derived oligosaccharides from milk than other species, however.

Lactose is about 40% as sweet as the disaccharide sucrose (glucose + fructose) but provides approximately the same amount of energy (16.5 kilojoules (3.9 Calories) per gram). Lactose is composed of the sugars glucose and galactose, and it has a glycemic index (GI) of 46 (low GI). In addition to lactose, the proteins in milk increase insulin secretion, which helps lower the glycemic response in most people (not those with type 1 diabetes). Finally, fat in milk helps lower the glycemic response by delaying gastric emptying. Therefore, it should come as no surprise that all plain milks and yoghurts naturally have a low GI. Unfortunately, most cheese doesn’t contain enough lactose to enable its GI to be measured, but if it did, it would also likely be low GI.

Adding sugars like sucrose (table or cane sugar) can raise milk and yoghurt’s GI, but because it (sucrose) has a medium GI (average=65), as long as its not added in excessive amounts, most sweetened milks and yoghurts will still have a low GI overall. Adding sugars and other carbohydrates will of course increase the amount of available carbohydrate and therefore the glycemic load, however.

It is important to remember that glycemic load is the strongest predictor of the effect of a food or drink on blood glucose and insulin levels. Therefore, increasing a food or drinks glycemic load may increase people’s insulin requirements – important for those people using exogenous insulin (i.e., injections/pumps).

When consumed in recommended amounts (2.5 – 4 serves a day for men and women), a serve of plain regular milk (1 Cup or 250 mL or 9 Oz) will provide 15.5 g of carbohydrate, have an average GI of 37 and therefore a glycemic load of 6 g (low). A serve of regular plain yoghurt (3/4 Cup or 200 g or 7 Oz) will provide 8.5 g of carbohydrate, have a GI of 17 and therefore a glycemic load of 2 (low).

Therefore, milk, yoghurt and other dairy foods can be enjoyed by people with diabetes as part of their healthy eating plan.

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