Unfortunately, the addition of glucogenic milk sugars and milk proteins can worsen the insulin punch from consumption of whey. Whey, soy, and caseinate milk proteins are enriched in glucogenic peptides - short proteins, easily and quickly assimilated within the first few feet of intestines, hydrolyzed (broken down) to release amino acids that are converted directly to glucose. This results in an exaggerated boost of insulin.
Since most of us use whey constantly during training, often substituting whey for meals at breakfast and at night as well, insulin boosting can backfire and result in impaired glucose synthesis, storage, utilization in muscle.