Association between zinc and body composition: An integrative review.

BACKGROUND: Zinc deficiency is related to lean body mass reduction, fat deposition, and obesity. Zinc acts in catalytic, structural, and regulatory functions, being an essential micronutrient to humans. It is crucial for maintaining lean body mass, synthesizing nucleic acids and proteins, and forming new tissues. Pre-existing zinc deficiency may contribute to obesity due to its relationship with fat deposition associated with short stature. This integrative review aims to analyze the association between zinc and body composition, hitherto very poorly established in previous studies. MATERIAL AND METHODS: The electronic databases utilized in this review were PubMed and Web of Science. We identified titles and abstracts from 1178 articles relating to zinc and body composition that were published in the last ten years. After duplicates were removed, the reference lists of relevant reviews were checked, and 47 articles were obtained by manual search. MAIN FINDINGS AND CONCLUSIONS: The articles were transversal or longitudinal studies, clinical trials, randomized controlled trials, reviews, systematic reviews, and meta-analysis. Although there was heterogeneity among the methodologies, the existence of an association between zinc and body composition was predominant among the studies. All articles concluded that zinc had positive effects on proteogenesis. Moreover, zinc metabolism is dysregulated in obese individuals, whose mechanisms remain controversial.

Validity of bioelectrical impedance to estimate fat-free mass in boys with Duchenne muscular dystrophy.

The evaluation of fat-free mass (FFM) in patients with Duchenne muscular dystrophy (DMD) is useful to investigate disease progression and therapeutic efficacy. This study aimed to validate the Bioelectrical impedance (BIA) method compared with the dual-energy X-ray absorptiometry (DXA) for estimating the %FFM in boys with DMD. This is a cross-sectional study performed with children and adolescents diagnosed with DMD. Resistance and reactance were measured with a BIA analyzer, from which eight predictive equations estimated the %FFM. The %FFM was also determined by DXA and its used as a reference method. Pearson correlation test, coefficient of determination, the root-mean-square error, the interclass correlation coefficient, and linear regression analysis were performed between %FFM values obtained by BIA and DXA. The agreement between these values was verified with the Bland-Altman plot analysis. Forty-six boys aged from 5 to 20 years were enrolled in the study. All the equations showed a correlation between the %FFM estimated by BIA and determined by DXA (p < 0.05). The Bland-Altman method indicated that two equations have a significant bias (p < 0.05) and six equations showed no significant bias of %FFM (p > 0.05). However, one of them has high variation and wide limits of agreement. Five of eight %FFM predictive equations tested in DMD were accurate when compared with the DXA. It can be concluded that BIA is a validity method to evaluate patients with DMD.