Topical Area: Energy and Macronutrient Metabolism
We sought to assess whether there are sex differences in postprandial amino acid (AA) responses to different quantities and sources of dietary protein.
In a randomized, crossover design, 12 participants [6 males, age: 29 ± 3 y; BMI: 27.1 ± 5.1 kg/m2; mean ± SEM, and 6 females, age: 30 ± 6 y; BMI: 25.0 ± 1.8 kg/m2] completed three 5-h acute feeding trials. They consumed breakfasts containing 10 g of protein from foods (10-PRO), 30 g of protein from foods (30-PRO), and 10 g of protein from foods with an additional 20 g of whey protein isolate (WPI) consumed 120 minutes later (10/20-PRO). Blood samples were collected at times -30, 0, 30, 60, 120, 150, 180, 240, and 300 min relative to breakfast intake.
Results : For each trial, protein intakes were quantitatively the same for females and males, which resulted in greater protein intakes for females when expressed per kg body mass and liter of plasma volume (Table 1). Plasma AA concentrations did not increase for either sex after 10-PRO (300 min time period) or the first 120 min of 10/20-PRO (before WPI consumed). Plasma total free amino acid (TAA), essential amino acid (EAA), and leucine concentrations (µg/mL) peaked at 240 min for males and at 150, 180, and 240 min respectively, for females, after 30-PRO. TAA, EAA, and leucine concentrations peaked 60 min after consuming 20 g WPI (180 min after breakfast) for 10/20-PRO for both sexes. No differences in composite iAUCpos over 300 min were observed between sexes for 30-PRO. Composite iAUCpos (µg/mL) over 300 min for TAA, EAA, and leucine were greater for females compared to males, by 41, 57, and 40% respectively, for 10/20-PRO.
Plasma AA responses to consuming a high-protein breakfast are not different between females and males, but are greater for females after consuming a whey protein supplement. This greater increase in AA concentrations for females may be due to greater rates of absorption and/or a greater quantity of protein intake relative to body mass and plasma volume. Males may require more whey protein than females to achieve comparable plasma AA responses.
Funding Sources :
Purdue University, Ingestive Behavioral Research Center and Lynn Fellowship to JLH