Plasma zinc, copper, and serum thyroid hormones and insulin levels after zinc supplementation followed by placebo in competitive athletes.
Intense physical activity is associated with biological adaptations involving hormones and trace elements. Zinc supplementation may affect plasma copper concentration, thyroid-stimulating hormone (TSH), thyroid hormones, insulin, and glucose homeostasis, but data in athletes are scarce. The aim of this study was to evaluate in competitive athletes (cyclists, n = 7, 32 ± 8 years) the effect of zinc supplementation (22 mg/day as zinc gluconate) during 30 days, and discontinuation using placebo (maltodextrin) during the following 30 days, on plasma zinc and copper concentrations, serum thyroid hormones, insulin and glucose levels, and HOMA2-IR. Compared to baseline, plasma zinc and Zn:Cu plasma ratio increased, but plasma copper decreased after zinc supplementation (day 30) and discontinuation (day 60) (p < 0.05). Zn supplementation and discontinuation had no effect on TSH, T3, and T4. Fasting serum insulin and HOMA2-IR increased (27% and 47%, respectively) on day 60 compared to baseline (p = 0.03), suggesting a delayed effect of zinc supplementation. Moreover, plasma zinc was positively associated with serum insulin (r = 0.87, p = 0.009) and HOMA2-IR (r = 0.81, p = 0.03) after zinc supplementation (day 30), indicating that supplemental zinc may impair glucose utilization in cyclists.
Marques
Lucianna Fernandes J C
LF
Instituto de Química, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
Donangelo
Carmen Marino
CM
Franco
Juliana Gastao
JG
Pires
Luciane
L
Luna
Aderval Severino
AS
Casimiro-Lopes
Gustavo
G
Lisboa
Patricia Cristina
PC
Koury
Josely Correa
JC
D000328:Adult; D003300:Copper / Q000097:blood*; D019587:Dietary Supplements; D006801:Humans; D007328:Insulin / Q000097:blood*; D008297:Male; D013963:Thyroid Hormones / Q000097:blood*; D055815:Young Adult; D015032:Zinc / Q000008:administration & dosage / Q000097:blood* / Q000494:pharmacology*
D007328:Insulin; D013963:Thyroid Hormones; D003300:Copper; D015032:Zinc