Glycemic and insulinemic responses to protein supplements

The effects of common servings of commercially marketed nutritional protein supplements on blood glucose and insulin responses were studied in 12 healthy men after ingestion of feedings that had varying carbohydrate and protein compositions.

Fasting subjects consumed a 50-gram glucose drink, a white bagel, peanuts, a protein bar, or a protein drink in a counterbalanced fashion.

Subjects rested in a supine position and were not disturbed while blood samples were drawn at rest and at 10-minute intervals during the ensuing 2 hours.

The area under the curve for glucose was greater in the glucose drink group vs all treatment groups except the white bagel group ( P <.05). At 20 to 40 minutes, plasma glucose was elevated in the glucose drink group vs the peanuts group, the protein bar group, and the protein drink group ( P <.05). The glycemic response was greater in the glucose drink group vs the white bagel group at 30 minutes (8.1+/-0.5 vs 6.5+/-0.3 mmol/L, respectively) ( P <.05). The area under the curve for insulin was lower in the peanuts group vs all treatment groups ( P <.05). Insulin concentrations peaked at 40 minutes in the glucose drink group (285.5+/-18.3 pmol) and was similar in all but the peanuts group (130.5+/-14.3 pmol) ( P <.05).

A common serving of a commercially available protein supplement resulted in a marked insulin response with no glycemic response because of the lack of carbohydrate content. Inasmuch as many such supplements similar in composition are marketed on the bases of their nutritional energy benefits, these data underscore the need to educate consumers regarding appropriate fuel for exercise and nutritional supplement composition.