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Am J Clin Nutr. 2005 Jun;81(6):1442-8.

Effect of protein supplementation during a 6-mo strength and conditioning program on insulin-like growth factor I and markers of bone turnover in young adults.

Author information

1
Applied Physiology Laboratory, South Dakota State University, Brookings, SD 57007, USA.

Erratum in

  • Am J Clin Nutr. 2006 Mar;83(3):723.

Abstract

BACKGROUND:

Exercise is beneficial for bone when adequate nutrition is provided. The role of protein consumption in bone health, however, is controversial.

OBJECTIVE:

The objective was to ascertain the effect of high protein intake on insulin-like growth factor I (IGF-I) and markers of bone turnover during 6 mo of exercise training.

DESIGN:

Fifty-one subjects aged 18-25 y (28 men, 23 women) received a protein supplement (42 g protein, 24 g carbohydrate, 2 g fat) or a carbohydrate supplement (70 g carbohydrate) twice daily. Exercise consisted of alternating resistance training and running 5 times/wk. Plasma concentrations of IGF-I, insulin-like growth factor-binding protein 3, serum bone alkaline phosphatase, and urinary N-telopeptide collagen crosslink (NTx) concentrations were measured at 0, 3, and 6 mo after 24 h without exercise and a 12-h fast.

RESULTS:

Three-day diet records indicated no difference in energy intake between the groups. Average protein intakes after supplementation began in the protein and carbohydrate groups were 2.2 +/- 0.1 and 1.1 +/- 0.1 g/kg, respectively (P < 0.001). The increase in plasma IGF-I was greater in the protein group than in the carbohydrate group (time x supplement interaction, P = 0.01). There were no significant changes over time or significant differences by supplement in plasma insulin-like growth factor-binding protein 3 (44 and 40 kDa). Serum bone alkaline phosphatase increased significantly over time (P = 0.04) and tended to be higher in the protein group than in the carbohydrate group (P = 0.06). NTx concentrations changed over time (time and time squared; P < 0.01 for both) and were greater in the protein group than in the carbohydrate group (P = 0.04). Men had higher NTx concentrations than did women (74.6 +/- 3.4 and 60.0 +/- 3.8 nmol/mmol creatinine; P = 0.005).

CONCLUSION:

Protein supplementation during a strength and conditioning program resulted in changes in IGF-I concentrations.

PMID:
15941900
DOI:
10.1093/ajcn/81.6.1442
[Indexed for MEDLINE]

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