title: Level of dietary protein intake affects glucose turnover in endurance-trained men.
abstract: 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.
  
  
  RESULTS
  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.
authors.affiliation: Department of Nutritional Sciences, University of Connecticut, Storrs, CT, USA. nancy.rodriguez@uconn.edu.
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Pasiakos
authors.forename: William F
authors.initials: WF
authors.lastname: Martin
authors.forename: Charu S
authors.initials: CS
authors.lastname: Sharma
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Pikosky
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Gaine
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Bolster
authors.forename: Brian T
authors.initials: BT
authors.lastname: Bennett
authors.forename: Nancy R
authors.initials: NR
authors.lastname: Rodriguez
references.citation: Am J Clin Nutr. 2008 May;87(5):1576S-1581S
references.pmid: 18469291
references.citation: Med Sci Sports Exerc. 2009 Mar;41(3):709-31
references.pmid: 19225360
references.citation: J Nutr. 2004 Apr;134(4):968S-73S
references.pmid: 15051856
references.citation: Am J Physiol. 1956 Sep;187(1):15-24
references.pmid: 13362583
references.citation: J Am Diet Assoc. 2002 Nov;102(11):1621-30
references.pmid: 12449285
references.citation: Diabetes. 2004 Sep;53(9):2375-82
references.pmid: 15331548
references.citation: Curr Opin Endocrinol Diabetes Obes. 2008 Oct;15(5):416-21
references.pmid: 18769212
references.citation: Eur J Clin Invest. 2005 Jun;35(6):351-4
references.pmid: 15948894
references.citation: Diabetologia. 2000 Oct;43(10):1257-65
references.pmid: 11079744
references.citation: J Appl Physiol (1985). 2000 Jan;88(1):246-56
references.pmid: 10642387
references.citation: Am J Physiol. 1998 Sep;275(3):E537-42
references.pmid: 9725823
references.citation: Metabolism. 2006 Apr;55(4):501-7
references.pmid: 16546481
references.citation: Physiol Rev. 1992 Apr;72(2):419-48
references.pmid: 1557428
references.citation: Am J Physiol Endocrinol Metab. 2005 Oct;289(4):E678-83
references.pmid: 15914508
references.citation: Metabolism. 1994 Dec;43(12):1481-7
references.pmid: 7990700
references.citation: J Nutr. 2003 Feb;133(2):405-10
references.pmid: 12566475
references.citation: Curr Opin Clin Nutr Metab Care. 2006 Jul;9(4):463-8
references.pmid: 16778578
references.citation: Am J Physiol. 1995 May;268(5 Pt 1):E1031-8
references.pmid: 7762630
references.citation: Diabetologia. 2003 Jul;46(7):917-25
references.pmid: 12819901
references.citation: Am J Clin Nutr. 2003 Oct;78(4):734-41
references.pmid: 14522731