Abstract
BackgroundThe optimal vitamin D intake for nursing mothers with overweight or obesity has not been defined. Vitamin D concentrations are associated with body composition indices, particularly body fat mass. Few studies have investigated the relationship between hypovitaminosis D, obesity, anthropometric status, and body composition in nursing women. Thus, the present study aims to investigate whether vitamin D supplementation during lactation will improve vitamin D status, reduce body fat mass, and improve body composition.Methods/designIn a double-blind, randomized, placebo-controlled, parallel-group trial, after term delivery, 90 healthy women with overweight or obesity will be selected and randomly allocated into three groups to receive 2000 IU/d cholecalciferol (vitamin D3), 4000 IU/d cholecalciferol, or placebo (lactose) for 12 weeks while nursing. Measurements of height, weight, waist circumference, and body composition (fat mass (kg), lean mass (kg), body fat (%), fat mass index, and relative fat mass index) will be taken for all subjects at baseline and after 12 weeks of intervention. In addition, serum 25-hydroxyvitamin D (25(OH)D), parathyroid hormone, calcium, and phosphorus will be measured.DiscussionThis study is the first investigating the effect of different amounts of vitamin D supplementation on serum calcidiol, anthropometric status, and body composition in nursing women with overweight or obesity. Our findings will contribute to the growing body of knowledge regarding the role of vitamin D supplementation in obesity, anthropometric status, and body composition in nursing women.Trial registrationIranian Registry of Clinical Trials IRCT20140413017254N6. Registered on 11 April 2018.
Highlights
The optimal vitamin D intake for nursing mothers with overweight or obesity has not been defined
This study is the first investigating the effect of different amounts of vitamin D supplementation on serum calcidiol, anthropometric status, and body composition in nursing women with overweight or obesity
Our findings will contribute to the growing body of knowledge regarding the role of vitamin D supplementation in obesity, anthropometric status, and body composition in nursing women
Summary
The optimal vitamin D intake for nursing mothers with overweight or obesity has not been defined. Nursing mothers expend 500 kcal per day for milk production [4], resulting in gradual weight loss [5, 6] Factors such as unhealthy dietary intake, low physical activity [7], higher leptin level [8], or pre-pregnancy body mass index (BMI) [9], and deficiency of serum 25-hydroxyvitamin D (25(OH)D; ≤ 20 ng/ml or 50 nmol/l) [10] are associated with more weight gain or obesity during pregnancy, which may lead to chronic diseases in nursing mothers [11]. The retention of vitamin D in body fats due to overweight in pregnancy [16], an increase in the body’s need for bone mass [17], lack of adequate sunlight exposure [18], and very low levels of vitamin D intake are the most significant reasons for deficiency of vitamin D in nursing mothers [19]
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