The Fat Content of Milk Does Not Affect the Plasma Glucose and Insulin Responses to a Meal
Authors: Li Jia , Janle Elsa , Campbell Wayne W 
Published: November 2023

ObjectiveThe purpose of this study was to assess the postprandial glycemic and insulinemic responses to isovolumetric and isocarbohydrate quantities of fluid milks including skim milk, low‐fat milk (1% fat), whole milk (3.5% fat), and water control consumed with a standard breakfast sandwich.MethodsForty‐six overweight and obese adults were recruited and categorized with normal glucose tolerance or prediabetes using HbA1c<5.7 and 5.7≤HbA1c<6.5% respectively. Twenty‐nine (20F/9M) individuals had normal glucose tolerance (BMI: 32.3±0.8kg/m2, Age: 50±2y, Mean±SE) and 17 (13F/4M) had prediabetes (BMI: 33±1.2kg/m2, Age: 49±3y). Each subject was provided with standardized meals to consume the day before each testing day. On 4 mornings separated by at least one week, each subject consumed a standard breakfast sandwich with one of the 4 beverages (240mL) in random order. The milk beverages each contained 12g of carbohydrate, and the digestible carbohydrate in the sandwich plus water, skim milk, low‐fat milk, or whole milk were 63, 75, 75, and 75g, respectively. Plasma glucose and insulin concentrations were measured from aliquots obtained before (fasting blood) and at 30‐minute intervals for 4 hours after consuming the meals. Incremental areas under the curve (AUC) were computed for glucose and insulin.ResultsPostprandial glucose AUC(0–4h) were not different among the beverages. During the first 2 hours, glucose AUC(0–2h) was higher for water vs. skim milk and whole milk (water: 2571±244a, skim milk: 2115±244b, low‐fat milk: 2342±244ab, and whole milk: 2043±244b mg/dL•min, abc: values with different letters were significantly different, p<0.05). No differences in glucose AUC(2–4h) were observed during the 2–4 hour period.Insulin AUC(0–4h) was lower for water compared to the milk beverages (water: 7515±772a, skim milk: 8719±772b, low‐fat milk: 9068±774b, and whole milk: 9315±772b μU/mL•min, p<0.05). During the first 2 hours, water had lower insulin AUC(0–2h) than low‐fat milk (6312 vs. 7109 μU/mL•min, p<0.05). During the 2–4 hour period, water had lower insulin AUC(2–4h) than the milk beverages and whole milk had the highest insulin AUC(2–4h) (water: 1203±236a, skim milk: 1909±236b, low‐fat milk: 1959±236b, whole milk: 2262±236c μU/mL•min, p<0.05).When the glucose and insulin responses were adjusted for the digestible carbohydrate content (by dividing the AUC by the digestible carbohydrate quantity for each test sandwich plus beverage), meals consumed with the milks had lower glucose AUC(0–2h) and glucose AUC(0–4h) than the meal with water, but insulin AUC(0–2h) and insulin AUC(0–4h) were not different than water.ConclusionFor middle‐aged adults who are overweight and obese, the fat content of milk does not influence the postprandial glycemic and insulinemic responses to a meal. Compared to water, consuming milk with a meal increases the postprandial insulin response, but does not increase the glycemic response despite the additional digestible carbohydrate in milk.Support or Funding InformationNational Dairy Council, NIH #UL1TR001108