Dietary predictors of the insulin-like growth factor system in adolescent females: results from the Dietary Intervention Study in Children (DISC).
BACKGROUND
The insulin-like growth factor (IGF) system is associated with the adult diet and chronic disease. Childhood diet may influence chronic disease through its effect on the IGF system; however, there is limited information describing the dietary predictors of the IGF system in adolescents.


OBJECTIVE
We examined associations between dietary food intake [fat, protein (animal and vegetable), carbohydrate, lactose, dietary fiber, calcium, zinc, and sodium] and serum IGF-I, IGF binding protein 1 (IGFBP-1), IGF binding protein 3 (IGFBP-3), and the IGF-I:IGFBP-3 molar ratio in adolescent females.


METHODS
One hundred fifty-nine adolescent females in the Dietary Intervention Study in Children (age range: 14-18 y; 0.2-6.3 y postmenarche) were included. The dietary intake was assessed via three 24-h dietary recalls. IGF-related biomarkers were determined by using radioimmunoassays. Associations between dietary intakes and biomarkers were assessed with Pearson's correlations and multivariable linear regression. Dietary intakes and biomarkers were logarithmically transformed; thus, beta coefficients represented percentages.


RESULTS
In analyses adjusted for energy, age, and time since menarche, significant correlations (P < 0.05) were as follows: IGF-I with total protein, lactose, calcium, and sodium; IGFBP-3 with total fat (inverse), lactose, fiber, and calcium; IGF-I/IGFBP-3 with lactose and calcium; and IGFBP-1 with vegetable protein. In multivariable analyses, significant predictors of IGF-I were energy (beta = 0.14, P < 0.05) and calcium (beta = 0.14, P < 0.01), the significant predictor of IGFBP-3 was calcium (beta = 0.07, P < 0.05), and significant predictors of IGFBP-1 were vegetable protein (beta = 0.49, P < 0.05) and body mass index-for-age percentile (beta = -0.01, P < 0.001).


CONCLUSIONS
This study provides evidence that dietary intake affects IGF-related biomarkers-particularly elevated calcium with IGF-I and IGFBP-3 and elevated vegetable protein with IGFBP-1-and, to our knowledge, is novel in reporting these associations in adolescent females. The Dietary Intervention Study in Children was registered at clinicaltrials.gov as NCT00000459.
Kerver
Jean M
JM
Department of Epidemiology, Michigan State University, East Lansing, MI, USA. kerverje@msu.edu
Gardiner
Joseph C
JC
Dorgan
Joanne F
JF
Rosen
Cliff J
CJ
Velie
Ellen M
EM
D000293:Adolescent; D015415:Biomarkers / Q000097:blood; D015992:Body Mass Index; D002136:Calcium, Dietary / Q000008:administration & dosage*; D004032:Diet; D015930:Diet Records; D004044:Dietary Proteins / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D016014:Linear Models; D010940:Plant Proteins / Q000008:administration & dosage*
D015415:Biomarkers; D002136:Calcium, Dietary; D004044:Dietary Proteins; D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D010940:Plant Proteins; D007334:Insulin-Like Growth Factor I