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Effectiveness of melatonin supplementation versus placebo on metabolic parameters among overweight night workers


Night shift work promotes chronic circadian desynchronization, which may lead to suppression of melatonin and metabolic disorders.


To evaluate the effectiveness of melatonin supplementation versus placebo on metabolic parameters (glucose, glycated hemoglobin, insulin, total cholesterol, HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol and triglycerides) of overweight night workers.


A randomized, double-blind, placebo-controlled crossover trial conducted with 26 nursing professionals who worked permanent night shifts. Intervention was carried out in two phases (three months each) and consisted of the administration of 3 mg of fast-release melatonin and placebo in the nights between shifts and days off, that is, only when the sleep was performed at night. Metabolic parameters were assessed from a single 12 hour fasting blood sample at the baseline and after each phase of intervention. To compare the effectiveness of melatonin and placebo, the percentages of improvement or worsening of the parameters after the proposed interventions were evaluated and the difference between the baseline and each group of intervention was calculated.


The mean age of the participants was 37.8 years (SE=1.1 years). Most of them were nurses (53.8%) and married (65.5%). The mean time working in the current night shift was 4.8 years (SE=0.8 years). It was verified that 50% of participants had a significant improvement in HDL-cholesterol levels after melatonin supplementation whereas 42.3% showed an improvement among those who took placebo. Although the proportion of participants who showed an improvement in glucose levels (46.2%); glycated hemoglobin (53.9%) and insulin (46.2%) after melatonin supplementation was higher compared to placebo (30.8%, 42.3% and 38.5%, respectively), no statistically significant effects were observed. No differences in proportions of total cholesterol, LDL, VLDL and triglyceride levels were found according to the group of intervention.


In comparison with placebo, melatonin supplementation was effective in improving HDL-cholesterol levels and showed a tendency to improve glucose, glycated hemoglobin and insulin levels.


Melatonin; Effectiveness; Nursing; Shift Work Schedule.


Área Clínica


Department of Epidemiology, Public Health Graduate Program, Catholic University of Santos - Sao Paulo - Brasil, Department of Health, Life Cycles and Society, School of Public Health, University of São Paulo - Sao Paulo - Brasil, Stress Research Institute, University of Stockholm, Stockholm, Sweden. - - Suécia


Patrícia Teixeira Santana , Adriana Sousa Duarte, Ananda Laís Felix Garrido, Gabriella Habib Rodrigues, Luciana Fidalgo Ramos Nogueira, Pollyanna Pellegrino, José Cipolla-Neto, Claudia Roberta Castro Moreno, Elaine Cristina Marqueze