Original Article
European Journal of Clinical Nutrition (2008) 62, 186–196; doi:10.1038/sj.ejcn.1602726; published online 9 May 2007
The effects of a high-fruit and -vegetable, high-fiber, low-fat dietary intervention on serum concentrations of insulin, glucose, IGF-I and IGFBP-3
Contributors: AF and VM designed the study elements related to serum concentrations of insulin, glucose, IGF-I and IGFBP-3. AF also analyzed the data and drafted the manuscript. VM also assisted in the preparation of the manuscript. RP provided statistical expertise and assisted in drafting the manuscript. LK provided statistical programming support and assisted in preparation of the manuscript. ATR performed the insulin and glucose assays and assisted in the preparation of the manuscript. CJR performed the IGF-I and IGFBP-3 assays and assisted in the preparation of the manuscript. EL and AS designed and directed the overall Polyp Prevention Study, assisted in the design of the study elements related to serum insulin, glucose, IGF-I and IGFBP-3, and assisted in preparing the manuscript.
A Flood1, V Mai2, R Pfeiffer3, L Kahle4, A T Remaley5, C J Rosen6, E Lanza7 and A Schatzkin3
- 1Division of Epidemiology, University of Minnesota, Minneapolis, MN, USA
- 2Department of Epidemiology and Preventive Medicine, University of Maryland School of Medicine, Baltimore, MD, USA
- 3Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA
- 4Information Management Services, Inc., Silver Spring, MD, USA
- 5Department of Laboratory Medicine, Clinical Center, National Institutes of Health, Bethesda, MD, USA
- 6Maine Center for Osteoporosis Research and Education, Bangor, ME, USA
- 7Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA
Correspondence: Dr A Flood, Division of Epidemiology, University of Minnesota, 1300 South Second Street, Suite 300, Minneapolis, MN 55454, USA. E-mail: flood@epi.umn.edu
Received 3 July 2006; Revised 18 January 2007; Accepted 8 February 2007; Published online 9 May 2007.
Abstract
Objective:
To determine the effects of dietary change on serum concentrations of insulin, glucose, IGF-I and IGFBP-3.
Subjects:
From among participants in a randomized clinical trial of men and women without a history of diabetes who were 35 years old or older and who had at least one histologically confirmed colorectal adenoma removed during a qualifying colonoscopy within the 6 months before randomization, 750 subjects were selected for this analysis.
Methods:
The authors analyzed fasting serum from 375 subjects with and 375 subjects without a recurrent polyp among participants in a randomized trial of a low-fat (20% of energy), high-fiber (18 g per 1000 kcals of energy intake) and high-fruit and -vegetable (5–8 servings per day) dietary intervention.
Results:
After 4 years of follow-up, IGF-I concentration in the intervention group (N=248) declined by 8.86 ng/ml (initial mean of 133 ng/ml) and 7.74 ng/ml (initial mean value of 139 ng/ml) in the non-intervention group (N=502). Based on an unpaired t-test, these declines were both statistically significant, but the difference between groups for the decline in IGF-I (1.12 ng/ml ((95% confidence interval, -3.24 to 5.48)) was not. After 4 years, concentrations of IGFBP-3, insulin and glucose were not statistically different from values at baseline, and there were no differences in these serum measures between the intervention and control groups. In analysis restricted to lean (body mass index <25 kg/m2) subjects only, however, glucose concentrations in the intervention group decreased by 0.28 mmol/l, while they increased in the control group by 0.01 mmol/l (t-test for mean differences P=0.0003) over 4 years.
Conclusions:
A low-fat, high-fiber, high-fruit and -vegetable dietary intervention had minimal impact on serum concentrations of insulin, glucose, IGF-I and IGFBP-3 overall, but in lean subjects the intervention resulted in a significant reduction in serum glucose concentration.
Keywords:
insulin, glucose, IGF-I, IGFBP-3, dietary intervention, fruits and vegetables, fiber
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