The relationship between vitamin D status and visceral adiposity among older adults remains unclear. This study aimed to investigate the association between serum vitamin D levels and visceral adipose tissue (VAT) among older Iranian adults. This cross-sectional study included older adults aged ≥ 60 years from the Amirkola Health and Aging Project. Serum 25-hydroxyvitamin D levels were measured by enzyme-linked immunosorbent assay. VAT was assessed using dual-energy X-ray absorptiometry. Furthermore, the relationship between vitamin D and VAT was examined through multiple linear regression analysis, adjusting for potential confounders. Of the 600 participants, 345 (57.5%) were males and 255 (42.5%) were females. Their mean age was 68.90 ± 6.97 years, and the mean vitamin D level was 60.50 ± 39.45 ng/mL. Serum vitamin D levels showed a weak negative association with VAT mass (β = −0.062, p = 0.012). In both sexes, VAT mass predictors followed a similar pattern. Body mass index (BMI; β = 0.811, p < 0.001) was identified as a strong predictor, while diabetes status exhibited a positive association with VAT mass (β = 0.078, p = 0.002). Serum vitamin D levels appear to have a weak inverse relationship with visceral adiposity in older Iranian adults. BMI was the most robust predictor of VAT. Further longitudinal research is needed to clarify the causal relationship between vitamin D status and visceral adiposity among older adults.
A randomized, double-blind, placebo-controlled trial was conducted to confirm whether collagen peptide supplementation for 12 week has a beneficial effect on body fat control in older adults at a daily physical activity level. Participants were assigned to either the collagen group (15 g/day of collagen peptide) or the placebo group (placebo drink). Body composition was measured by bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DEXA). In total, 74 participants (collagen group, n = 37; placebo group, n = 37) were included in the final analysis. The collagen group showed a significant reduction in total body fat mass compared with the placebo group, as evidenced by both BIA (p = 0.021) and DEXA (p = 0.041) measurements. Body fat mass and percent body fat of the whole body and trunk reduced at 12 weeks compared with baseline only in the collagen group (whole body: body fat mass, p = 0.002; percent body fat, p = 0.002; trunk: body fat mass, p = 0.001; percent body fat, p = 0.000). Total fat mass change (%) (collagen group, −0.49 ± 3.39; placebo group, 2.23 ± 4.20) showed a significant difference between the two groups (p = 0.041). Physical activity, dietary intake, and biochemical parameters showed no significant difference between the groups. The results confirmed that collagen peptide supplementation had a beneficial effect on body fat reduction in older adults aged ≥ 50 years with daily physical activity level. Thus, collagen peptide supplementation has a positive effect on age-related changes.
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Our aim was to conduct a systematic review and meta-analysis on randomized controlled trials (RCTs) evaluating the effect of garlic on serum adiponectin levels. We searched Scopus, Web of Science, PubMed, and Cochrane Library to databases up to January 2021. RCTs investigating the effects of garlic on serum adiponectin levels in adult participants were included. The change in serum adiponectin levels was estimated using weighted mean differences (WMD) and standard deviations (SD). The random effects model was used to provide a summary of mean estimates and their SDs. Out of 386 records, 6 trials with 8 arms treatment which enrolled 266 subjects were included. Garlic supplementation resulted in a non-significant increase in adiponectin concentrations when compared to placebo, according to the pooled data (WMD, 0.27 Hedges' g; 95% confidence interval [CI], −0.07, 0.62; p = 0.124). Greater effects on adiponectin were observed in trials with supplementation dose less than 1.5 gram per day (WMD, 0.71 Hedges' g; 95% CI, −0.01, 1.43; p = 0.600) and in trials with female subset (WMD, 0.62 Hedges' g; 95% CI, −0.96, 2.21; p = 0.441). Garlic boosts adiponectin levels in general. However, due to different target population, various units for reporting adiponectin level and few eligible studies in final analysis, more research is needed to get a firm conclusion about the influence of garlic on adiponectin levels.
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