Vitamin DNEW2026

Vitamin D supplementation and central adiposity in male shift workers: a randomized clinical trial on metabolic health.

Menezes-Júnior Luiz, Fajardo Virgínia Capistrano, Oliveira Fernando Luiz Pereira de, Coelho George Luiz Lins Machado et al. — Sao Paulo medical journal = Revista paulista de medicina

Summary

This study investigated whether taking vitamin D supplements could help reduce belly fat in male shift workers, a group often prone to low vitamin D and metabolic issues. Researchers found that while vitamin D levels in the blood increased significantly with supplementation, it did not lead to a decrease in belly fat. This suggests that vitamin D alone might not be enough to tackle obesity-related problems in this specific population.

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Key points

A study examined if vitamin D supplements could reduce belly fat in male shift workers.
Participants with low vitamin D and metabolic issues received either a placebo or vitamin D supplements for four months.
While vitamin D levels in the blood significantly increased, there was no change in belly fat measurements.
This suggests vitamin D supplementation alone may not be effective for reducing central obesity in this group.

What the study looked at

What question did the study ask? Researchers wanted to know if taking vitamin D supplements could help reduce central adiposity, or belly fat, in male shift workers who often have low vitamin D levels and a higher risk of metabolic issues. How was it studied? This was a randomized, double-blind, placebo-controlled clinical trial involving 198 male shift workers from an iron ore company in Brazil. Participants with low vitamin D and at least one metabolic abnormality were randomly assigned to receive either a placebo, 14,000 IU of vitamin D per week, or 28,000 IU of vitamin D per week for four months. Their vitamin D levels and measurements of belly fat (waist circumference and waist-to-height ratio) were checked before and after the intervention. What did it find? The study found that while vitamin D supplementation significantly increased blood vitamin D levels in the treatment groups, it did not lead to any significant reduction in waist circumference or waist-to-height ratio compared to the placebo group. This indicates that increasing vitamin D levels through supplements alone did not help reduce belly fat in these male shift workers.

Dietary takeaway

This study suggests that simply taking vitamin D supplements might not be enough to reduce belly fat, even if your vitamin D levels are low. While vitamin D is important for overall health, focusing solely on supplements for weight management may not yield desired results. Remember, this is just one study, and a balanced diet rich in various nutrients, along with regular physical activity, remains key for managing weight and metabolic health.

Abstract

BACKGROUND: Vitamin D deficiency is common among individuals with obesity; however, the association between low 25-hydroxyvitamin D [25(OH)D] concentrations and adiposity remains unclear. Shift workers are at increased risk for both vitamin D deficiency and metabolic disorders, making this population particularly relevant for investigating this relationship. OBJECTIVES: This study aimed to evaluate the effect of cholecalciferol supplementation on central adiposity, assessed by waist circumference (WC) and waist-to-height ratio (WHtR), among male shift workers. DESIGN AND SETTING: Randomized, double-blind, placebo-controlled clinical trial involving 198 male shift workers employed by an iron ore extraction company in Minas Gerais, Brazil. METHODS: Participants with 25(OH)D concentrations <30 ng/mL and at least one metabolic abnormality, including metabolic syndrome, impaired fasting glucose, dyslipidemia, elevated blood pressure, or increased WC, were randomly assigned to receive placebo, cholecalciferol 14,000 IU/week, or cholecalciferol 28,000 IU/week for 4 months. Plasma 25(OH)D concentrations, WC, and WHtR were evaluated at baseline and post-intervention. RESULTS: After 4 months, no significant differences in WC or WHtR were observed between the vitamin D supplementation groups (14,000 IU/week and 28,000 IU/week) and the placebo group. Nevertheless, serum 25(OH)D concentrations increased significantly in the supplementation groups: +6.23 ng/mL (p25 = 0.58; p75 = 10.61) in the 14,000 IU/week group and +15.25 ng/mL (p25 = 10.57; p75 = 19.68) in the 28,000 IU/week group. In contrast, the placebo group showed a decrease of -0.50 ng/mL (p25 = -1.03; p75 = 2.71). Despite these increases, supplementation produced no significant effect on central adiposity outcomes (p > 0.05). CONCLUSION: Although vitamin D supplementation effectively increased serum 25(OH)D concentrations, it did not reduce central adiposity among male shift workers. These findings indicate that vitamin D supplementation alone is unlikely to improve obesity-related outcomes in this high-risk occupational population and underscore the need for comprehensive strategies targeting metabolic health in shift workers. CLINICAL TRIAL OR SYSTEMATIC REVIEW REGISTRATION: This study was registered in the Brazilian Registry of Clinical Trials (ReBEC) under identifier RBR-6CS352 on October 25, 2017.

View on PubMed →DOI: 10.1590/1516-3180.2025.2955.18032026