Level of dietary protein intake affects glucose turnover in endurance-trained men

Journal of the International Society of Sports Nutrition, Nov 2011

Background To examine the effects of higher-protein diets on endogenous glucose metabolism in healthy, physically active adults, glucose turnover was assessed in five endurance-trained men (age 21.3 ± 0.3 y, VO2peak 70.6 ± 0.1 mL kg-1 min-1) who consumed dietary protein intakes spanning the current dietary reference intakes. Findings Using a randomized, crossover design, volunteers consumed 4 week eucaloric diets providing either a low (0.8 g kg-1 d-1; LP), moderate (1.8 g kg-1 d-1; MP), or high (3.6 g kg-1 d-1; HP) level of dietary protein. Glucose turnover (Ra, glucose rate of appearance; and Rd glucose rate of disappearance) was assessed under fasted, resting conditions using primed, constant infusions of [6,6-2H2] glucose. Glucose Ra and Rd (mg kg-1 min-1) were higher for MP (2.8 ± 0.1 and 2.7 ± 0.1) compared to HP (2.4 ± 0.1 and 2.3 ± 0.2, P < 0.05) and LP (2.3 ± 0.1 and 2.2 ± 0.1, P < 0.01) diets. Glucose levels (mmol/L) were not different (P > 0.05) between LP (4.6 ± 0.1), MP (4.8 ± 0.1), and HP (4.7 ± 0.1) diets. Conclusions Level of protein consumption influenced resting glucose turnover in endurance athletes in a state of energy balance with a higher rate of turnover noted for a protein intake of 1.8 g kg-1 d-1. Findings suggest that consumption of protein in excess of the recommended dietary allowance but within the current acceptable macronutrient distribution range may contribute to the regulation of blood glucose when carbohydrate intake is reduced by serving as a gluconeogenic substrate in endurance-trained men.

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Level of dietary protein intake affects glucose turnover in endurance-trained men

Journal of the International Society of Sports Nutrition Level of dietary protein intake affects glucose turnover in endurance-trained men Stefan M Pasiakos 0 William F Martin 0 Charu S Sharma 0 Matthew A Pikosky 0 Patricia C Gaine 0 Douglas R Bolster 0 Brian T Bennett 0 Nancy R Rodriguez 0 0 Department of Nutritional Sciences, University of Connecticut , Storrs, CT , USA Background: To examine the effects of higher-protein diets on endogenous glucose metabolism in healthy, physically active adults, glucose turnover was assessed in five endurance-trained men (age 21.3 ± 0.3 y, VO2peak 70.6 ± 0.1 mL kg-1 min-1) who consumed dietary protein intakes spanning the current dietary reference intakes. Findings: Using a randomized, crossover design, volunteers consumed 4 week eucaloric diets providing either a low (0.8 g kg-1 d-1; LP), moderate (1.8 g kg-1 d-1; MP), or high (3.6 g kg-1 d-1; HP) level of dietary protein. Glucose turnover (Ra, glucose rate of appearance; and Rd glucose rate of disappearance) was assessed under fasted, resting conditions using primed, constant infusions of [6,6-2H2] glucose. Glucose Ra and Rd (mg kg-1 min-1) were higher for MP (2.8 ± 0.1 and 2.7 ± 0.1) compared to HP (2.4 ± 0.1 and 2.3 ± 0.2, P < 0.05) and LP (2.3 ± 0.1 and 2.2 ± 0.1, P < 0.01) diets. Glucose levels (mmol/L) were not different (P > 0.05) between LP (4.6 ± 0.1), MP (4.8 ± 0.1), and HP (4.7 ± 0.1) diets. Conclusions: Level of protein consumption influenced resting glucose turnover in endurance athletes in a state of energy balance with a higher rate of turnover noted for a protein intake of 1.8 g kg-1 d-1. Findings suggest that consumption of protein in excess of the recommended dietary allowance but within the current acceptable macronutrient distribution range may contribute to the regulation of blood glucose when carbohydrate intake is reduced by serving as a gluconeogenic substrate in endurance-trained men. Introduction Increasing dietary protein at the expense of carbohydrate in either Type 2 diabetics or in overweight adults in response to energy restriction improves insulin sensitivity and glycemic control [ 1-5 ]. Studies have shown that protein intake in excess of the current recommended dietary allowance (RDA: 0.8 g kg-1 d-1) stabilizes blood glucose and reduces the postprandial insulin response after weight loss [ 2,3 ]. The metabolic advantage of a diet which provides dietary protein above the RDA specific to glucose utilization in healthy, physically active adults is unclear [6]. Higher-protein intakes are recommended for physically active adults who routinely participate in endurance exercise [ 7-9 ]. To date, no studies have investigated the impact of dietary protein intake on glucose homeostasis in endurance-trained adults. The objective of our study was to examine the effects of consuming dietary protein intakes spanning the current Acceptable Macronutrient Distribution Range (AMDR) on resting glucose turnover in endurance-trained men [ 10 ]. We hypothesized that protein availability would influence glucose turnover during a eucaloric state such that glucose rate of appearance (Ra) would be greater when the proportion of energy derived from dietary protein was increased with a simultaneous reduction in carbohydrate consumption. Methods Using a randomized, crossover design, five endurancetrained men (21.3 ± 0.3 y, 179.1 ± 1.6 cm, 70.6 ± 0.1 kg, 8.7 ± 0.4% fat, VO2peak 70.6 ± 0.1 mL kg-1 min-1) were assigned to a diet providing 0.8 (Low Protein; LP), 1.8 (Moderate Protein; MP) or 3.6 (High Protein; HP) grams of protein per kilogram body mass per day for four weeks. Participants crossed over and consumed each of the remaining diets in randomized order following a 2 wk wash out period between each diet intervention. Actual macronutrient composition of the each diet was 48% carbohydrate (5.4 g kg-1 d-1), 26% fat, and 26% protein (3.1 g kg-1 d-1) for HP, 60% carbohydrate (7.4 g kg-1 d-1), 26% fat, and 14% protein (1.8 g kg-1 d-1) for MP, and 66% carbohydrate (8.3 g kg-1 d-1), 27% fat, and 7% protein (0.9 g kg-1 d-1) for LP. Extended details of the diet intervention have been previously reported [ 8 ]. Volunteers maintained their normal level of training throughout the study. However, exercise was restricted for 24 h before glucose turnover assessments to minimize the potential influence of previous exercise on study measures. Glucose turnover was assessed after 3 wks of each 4 wk diet intervention using a 120 min primed, constant infusion of [6,6-2H2] glucose (17 μmol kg-1; 0.2 μmol kg-1 min-1; Cambridge Isotope Laboratories, Andover, MA) at 0700 h after an overnight fast (≥ 10 h). Arterialized blood samples were obtained from a dorsal hand vein at baseline, 60, 75, 90, 105 and 120 min to determine glucose turnover, insulin, and glucose concentrations. Plasma enrichment of [6,6-2H2] glucose was determined in duplicate with a precision of ± 0.2% SD using a Hewlett Packard 5989A GC-MS (Metabol (...truncated)


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Stefan M Pasiakos, William F Martin, Charu S Sharma, Matthew A Pikosky, Patricia C Gaine, Douglas R Bolster, Brian T Bennett, Nancy R Rodriguez. Level of dietary protein intake affects glucose turnover in endurance-trained men, Journal of the International Society of Sports Nutrition, 2011, pp. 20, 8, DOI: 10.1186/1550-2783-8-20