The relation between nutritional factors and insulin–like growth factor–I in premenopausal women of different ethnicity

Summary

Background

Alterations in the insulin–like growth factor–I (IGF–I) system have been proposed as a metabolic link between nutritional factors and cancer risk.

Aim of the study

This study explored dietary determinants of circulating IGF–I and IGF binding protein–3 (IGFBP–3) levels among premenopausal women from different ethnic groups.

Methods

In a cross–sectional design, 258 women with a mean age of 43 ± 2.7 years donated blood approximately 5 days after ovulation and completed a validated Food Frequency Questionnaire. The majority of the 97 Caucasian, 96 Asian, and 65 Mixed/Other subjects were born in the US. Serum concentrations of IGF–I and IGFBP–3 were measured by double–antibody ELISA. After creating quartiles for 13 food and 13 nutrient density variables, leastsquare means of IGF–I, IGFBP–3, and the IGF–I/IGFBP–3 ratio were calculated by quartile, while adjusting for age, ethnicity, body mass index, and year of laboratory analysis.

Results

Whereas body mass index and dietary intakes varied significantly by ethnicity, IGF–I, IGFBP–3, and their ratio were similar by group. As the only food, fish showed a suggestive inverse association with IGF–I and the IGF–I/ IGFBP–3 ratio. Dietary fiber and vitamin A were positively related to IGF–I (p = 0.004 and 0.03), zinc with IGFB–3 (p = 0.0008), and iron with the IGF–I/IGFBP–3 ratio (p = 0.048), but the differences between the bottom and top quartile were less than 10%. Total energy, protein, carbohydrates, and total fat intake were not related to any serum measurements.

Conclusions

This study detected no ethnic differences in serum IGF–I, but it showed weak associations with dietary variables that require further investigation.