Effect of calorie restriction or protein intake on circulating levels of insulin like growth factor I in humans: A systematic review and meta-analysis

Asma Kazemi; John R Speakman; Sepideh Soltani; Kurosh Djafarian

doi:10.1016/j.clnu.2019.07.030

Effect of calorie restriction or protein intake on circulating levels of insulin like growth factor I in humans: A systematic review and meta-analysis

Asma Kazemi, John R Speakman^*, Sepideh Soltani, Kurosh Djafarian

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

19 Citations (Scopus)

Abstract

Calorie restriction (CR) and reductions in protein intake in rodents result in increased lifespan and reduced levels of IGF-1. However, the changes in IGF-1 in humans in response to CR and elevated protein intake are confused. We conducted a systematic review and meta-analysis to investigate the effect of Calorie restriction (CR) or increase in protein intake on IGF-1 in humans. The systematic review protocols have been developed based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines. Two separate systematic searches were undertaken: first for the effect of CR and second on the effect of increase in protein intake on IGF-1. PubMed, SCOPUS and ISI Web of Science databases were searched. In the meta-analysis of the calorie restriction studies, twelve studies met the inclusion criteria (8 clinical trials and 4 observational studies). The meta-analysis of both clinical trials and observational studies revealed no significant effect of CR on IGF-1 (clinical trials: standardized mean difference (SMD) = 0.002 ng/ml, 95% CI -0.14 to 0.14 ng/ml, p = 0.98; observational studies (SMD = -1.14 ng/ml, 95% CI -1.9 to -0.38 ng/ml, p = 0.003). In the meta-analysis of protein intake studies (six studies), a significant increase in circulating IGF-1 levels in response to increases in dietary protein was revealed (SMD = 0.4 ng/ml, 95% CI 0.18-0.61 ng/ml, p < 0.001). In conclusion, in humans, CR was not associated with a significant change in circulating IGF-1. However an increase in protein intake was associated with increased levels of circulating IGF-1.

PROTOCOLS REGISTRATION NUMBER: CRD42017073149 for the protein intake meta-analysis and CRD42016046260 for CR meta-analysis.

Original language	English
Pages (from-to)	1705-1716
Number of pages	12
Journal	Clinical Nutrition
Volume	39
Issue number	6
Early online date	10 Aug 2019
DOIs	https://doi.org/10.1016/j.clnu.2019.07.030
Publication status	Published - 1 Jun 2020

Bibliographical note

This work was not supported by any external funding. During this work JRS was supported by a Wolfson merit award from the Royal Society and a 1000 talents professorship from the Chinese Government.

Keywords

IGF-I
Calorie restriction
Protein intake
Ageing
Insulin like growth factor 1

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Cite this

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title = "Effect of calorie restriction or protein intake on circulating levels of insulin like growth factor I in humans: A systematic review and meta-analysis",

abstract = "Calorie restriction (CR) and reductions in protein intake in rodents result in increased lifespan and reduced levels of IGF-1. However, the changes in IGF-1 in humans in response to CR and elevated protein intake are confused. We conducted a systematic review and meta-analysis to investigate the effect of Calorie restriction (CR) or increase in protein intake on IGF-1 in humans. The systematic review protocols have been developed based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines. Two separate systematic searches were undertaken: first for the effect of CR and second on the effect of increase in protein intake on IGF-1. PubMed, SCOPUS and ISI Web of Science databases were searched. In the meta-analysis of the calorie restriction studies, twelve studies met the inclusion criteria (8 clinical trials and 4 observational studies). The meta-analysis of both clinical trials and observational studies revealed no significant effect of CR on IGF-1 (clinical trials: standardized mean difference (SMD) = 0.002 ng/ml, 95% CI -0.14 to 0.14 ng/ml, p = 0.98; observational studies (SMD = -1.14 ng/ml, 95% CI -1.9 to -0.38 ng/ml, p = 0.003). In the meta-analysis of protein intake studies (six studies), a significant increase in circulating IGF-1 levels in response to increases in dietary protein was revealed (SMD = 0.4 ng/ml, 95% CI 0.18-0.61 ng/ml, p < 0.001). In conclusion, in humans, CR was not associated with a significant change in circulating IGF-1. However an increase in protein intake was associated with increased levels of circulating IGF-1. PROTOCOLS REGISTRATION NUMBER: CRD42017073149 for the protein intake meta-analysis and CRD42016046260 for CR meta-analysis.",

keywords = "IGF-I, Calorie restriction, Protein intake, Ageing, Insulin like growth factor 1",

author = "Asma Kazemi and Speakman, {John R} and Sepideh Soltani and Kurosh Djafarian",

note = "This work was not supported by any external funding. During this work JRS was supported by a Wolfson merit award from the Royal Society and a 1000 talents professorship from the Chinese Government.",

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T2 - A systematic review and meta-analysis

AU - Kazemi, Asma

AU - Speakman, John R

AU - Soltani, Sepideh

AU - Djafarian, Kurosh

N1 - This work was not supported by any external funding. During this work JRS was supported by a Wolfson merit award from the Royal Society and a 1000 talents professorship from the Chinese Government.

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N2 - Calorie restriction (CR) and reductions in protein intake in rodents result in increased lifespan and reduced levels of IGF-1. However, the changes in IGF-1 in humans in response to CR and elevated protein intake are confused. We conducted a systematic review and meta-analysis to investigate the effect of Calorie restriction (CR) or increase in protein intake on IGF-1 in humans. The systematic review protocols have been developed based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines. Two separate systematic searches were undertaken: first for the effect of CR and second on the effect of increase in protein intake on IGF-1. PubMed, SCOPUS and ISI Web of Science databases were searched. In the meta-analysis of the calorie restriction studies, twelve studies met the inclusion criteria (8 clinical trials and 4 observational studies). The meta-analysis of both clinical trials and observational studies revealed no significant effect of CR on IGF-1 (clinical trials: standardized mean difference (SMD) = 0.002 ng/ml, 95% CI -0.14 to 0.14 ng/ml, p = 0.98; observational studies (SMD = -1.14 ng/ml, 95% CI -1.9 to -0.38 ng/ml, p = 0.003). In the meta-analysis of protein intake studies (six studies), a significant increase in circulating IGF-1 levels in response to increases in dietary protein was revealed (SMD = 0.4 ng/ml, 95% CI 0.18-0.61 ng/ml, p < 0.001). In conclusion, in humans, CR was not associated with a significant change in circulating IGF-1. However an increase in protein intake was associated with increased levels of circulating IGF-1. PROTOCOLS REGISTRATION NUMBER: CRD42017073149 for the protein intake meta-analysis and CRD42016046260 for CR meta-analysis.

AB - Calorie restriction (CR) and reductions in protein intake in rodents result in increased lifespan and reduced levels of IGF-1. However, the changes in IGF-1 in humans in response to CR and elevated protein intake are confused. We conducted a systematic review and meta-analysis to investigate the effect of Calorie restriction (CR) or increase in protein intake on IGF-1 in humans. The systematic review protocols have been developed based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines. Two separate systematic searches were undertaken: first for the effect of CR and second on the effect of increase in protein intake on IGF-1. PubMed, SCOPUS and ISI Web of Science databases were searched. In the meta-analysis of the calorie restriction studies, twelve studies met the inclusion criteria (8 clinical trials and 4 observational studies). The meta-analysis of both clinical trials and observational studies revealed no significant effect of CR on IGF-1 (clinical trials: standardized mean difference (SMD) = 0.002 ng/ml, 95% CI -0.14 to 0.14 ng/ml, p = 0.98; observational studies (SMD = -1.14 ng/ml, 95% CI -1.9 to -0.38 ng/ml, p = 0.003). In the meta-analysis of protein intake studies (six studies), a significant increase in circulating IGF-1 levels in response to increases in dietary protein was revealed (SMD = 0.4 ng/ml, 95% CI 0.18-0.61 ng/ml, p < 0.001). In conclusion, in humans, CR was not associated with a significant change in circulating IGF-1. However an increase in protein intake was associated with increased levels of circulating IGF-1. PROTOCOLS REGISTRATION NUMBER: CRD42017073149 for the protein intake meta-analysis and CRD42016046260 for CR meta-analysis.

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