EFFECTS OF ZINC AND OTHER NUTRITIONAL FACTORS ON INSULIN-LIKE-GROWTH-FACTOR-I AND INSULIN-LIKE-GROWTH-FACTOR BINDING-PROTEINS IN POSTMENOPAUSAL WOMEN

Insulin-like growth factor I (IGF-I) is a critical factor in the regul ation of various physiologic effects, including bone formation and pro tein metabolism. Nutrient intake is a main regulator of circulating IG F-I. The relation of zinc status and IGF-I in adulthood has not been s tudied adequately even though suboptimal intakes of zinc are reported widely in the elderly. This study examined the relation between calcul ated nutrient intakes from 119 postmenopausal women and concentrations of IGF-I and IGF binding proteins (IGFBPs). Dietary intake was evalua ted by 4-d weighed diet records at baseline and 2 y. Mean intakes of 2 5 nutrients were calculated. Concentrations of IGF-I and IGFBPs were m easured by radioimmunoassays at baseline and 2 y. Mean age (63 +/- 4 y ), weight (66 +/- 9 kg), and nutrient intake were correlated with the mean IGF-I concentration at baseline (172 +/- 57 mu g/L) and 2 y (142 +/- 43 mu g/L). IGF-I concentrations were significantly correlated wit h mean protein and zinc intake at baseline (r = 0.313, P = 0.001; r = 0.298, P = 0.001, respectively) and 2 y (r = 0.256, P = 0.008; r = 0.3 31, P = 0.001, respectively). After age, weight, and other nutrient in takes were adjusted for in multiple regression at baseline and 2 y, zi nc remained the major determinant of IGF-I concentrations. These resul ts suggest that low zinc intake is associated with low IGF-I concentra tions in healthy postmenopausal women and that the effects of zinc may be independent of protein intake.