Dairy products have the peculiar property of triggering pancreatic release of insulin. The research group at Lund University in Sweden have contributed the most to documenting this phenomenon:
Mean (±SEM) incremental changes (Δ) in serum insulin in response to equal amounts of carbohydrate from a white-wheat-bread reference meal ( x ) and test meals of whey (○), milk (♦), cheese (▵), cod (□), gluten-low (▴), and gluten-high (▾) meals. From Nilsson 2004 .
Note that it is the area under the curve (AUC), not the peak value, that assumes greatest importance.
Dairy products, especially milk, whey, and yogurt, are insulin secretagogues: they stimulate pancreatic release of insulin. The effect is likely due to amino acids and/or polypeptides in dairy products. (The effect is less prominent with cheese. Also see this study.)
By conventional wisdom, this may be a good thing, since the excess insulin will blunt the glucose rise after consumption. However, in my book, this is not such a good thing, since most of us have tired, beaten, overworked pancreatic beta cells from our decades of carbohydrate overconsumption. I fear that the effect of dairy products just take us a bit closer to beta cell failure: diabetes.
Good news: The effect is least with cheese.