Most milk products induce postprandial hypoglycemia within 50 minutes of consumption; in other words, milk products play havoc with blood sugar control. Carbohydrates, notably white bread, cause blood sugar and insulin levels to rise (postprandial glycemia). The glycemic index was developed in order to quantify the extent of the blood sugar increase. White bread is the reference point with a glycemic index of 100. Similarly, white bread with a value of 100 is also the reference point for the insulinemic index that quantifies the rise in insulin after consumption of carbohydrates. Research has shown that consuming a diet with a low glycemic index improves blood sugar control and cholesterol levels and reduces the risk of heart attacks and type 2 diabetes. It has generally been assumed that foods with a low glycemic index also have a low insulinemic index. Researchers at the University of Lund now challenge this assumption at least when it comes to milk products. After carrying out several laboratory experiments using human volunteers the researchers conclude that even though regular milk has a glycemic index of only 30 its insulinemic index is 90. Fermented milk products, which have very low glycemic indexes of 15, were found to have insulinemic indexes of 98.

The researchers speculated that organic acids such as vinegar might reduce the insulinemic index of the standard milk and carbohydrate breakfast. They compared a breakfast of white bread plus regular milk (250 grams) plus fresh cucumber (50 grams) [meal 1] with one of white bread plus yogurt (250 grams) plus pickled cucumber (50 grams) [meal 2]. They found that the glycemic and insulinemic index for meal 1 was 79 and 117 respectively as compared to meal 2 where the values were 55 and 79 respectively. The researchers conclude that the vinegar in the pickled cucumber is responsible for the highly significant and beneficial reduction in insulinemic index (they had previously found that yogurt did not reduce it). They conclude that milk, despite its relatively low glycemic index, increases the insulinemic index quite considerably while organic acids such as vinegar decrease it.
Ostman, Elin M., et al. Inconsistency between glycemic and insulinemic responses to regular and fermented milk products. American Journal of Clinical Nutrition, Vol. 74, July 2001, pp. 96-100