Background: We investigated the association between plant-based diets indices – an overall plant-based diet index; a healthful plant-based diet index; and an unhealthful plant-based diet index – and metabolic syndrome among Iranian older adults. Aim: We aimed to examine the relationship between plant-based diet indices and metabolic syndrome. Methods: This cross-sectional study included 178 older adults (51 men and 127 women), with a mean age of 67.04 (60–83) who were referred to health centers in Tehran, Iran. Blood and urine samples were collected to measure serum total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglycerides. We created an overall plant-based diet index, healthful plant-based diet index, and unhealthful plant-based diet index from semi-quantitative food-frequency questionnaire data. Anthropometric measures were done. Results: Our crude model results showed that triglycerides, systolic and diastolic blood pressure, fasting blood sugar, high-density lipoprotein cholesterol, and waist circumference did not significantly differ between tertiles of plant-based diet index and healthful plant-based diet index; also triglycerides, systolic and diastolic blood pressure, fasting blood sugar, and waist circumference did not significantly differ between tertiles of unhealthful plant-based diet index, but high-density lipoprotein cholesterol significantly differed between tertiles of unhealthful plant-based diet index. After adjusting for confounders the results remained non-significant for plant-based diet index but high-density lipoprotein cholesterol was significant for healthful and unhealthful plant-based diet indices. There was also no significant association between plant-based diet index (OR: 1.11; 95% CI: 0.53–2.33), healthful plant-based diet index (OR: 0.81; 95% CI: 0.39–1.68), and unhealthful plant-based diet index (OR: 0.81; 95% CI: 0.38–1.72) with metabolic syndrome, even after adjustment for confounders. Conclusions: Our findings showed that plant-based diets are not significantly associated with risk of metabolic syndrome in older adults. To confirm the veracity of these findings, more studies should be conducted.
ObjectivesPrevious studies showed that melatonin supplementation may suppress oxidative stress, however, the results have not been consistent. So, we conducted this meta-analysis to assess the precise relationship between melatonin supplementation and oxidative stress.MethodsPubMed and Scopus were searched for randomized controlled trials that investigated the effect of melatonin supplementation on oxidative stress up to March 2020. Heterogeneity was assessed by Cochran’s Q test and I-square (I2) statistic. Data were pooled using the random effect model and standardized mean difference (SMD) was considered as the summary effect size. Also, standard methods were used for assessment of sensitivity analysis and publication bias.ResultsWe included 15 related articles and our findings indicated that melatonin supplementation significantly increased total antioxidant capacity (TAC) level (SMD: 1.03, 95% CI: 0.24, 1.81, p=0.011) and reduced protein carbonyl (PCO) (SMD: −1.78, 95% CI: −2.97, −0.58, p=0.004) and malondialdehyde (MDA) levels (SMD: −0.94, 95% CI: −1.48, −0.40, p=0.001). Additionally, there was considerable effect on TAC level by using ≥20 mg/d melatonin and in people under 35 years old. MDA level also decreased using dosage of below 20 mg/d and in people ≥35 years old.ConclusionsThe present study showed a promising effect of melatonin administration for reducing MDA, PCO, and increasing TAC levels. However, further studies especially with more attention to PCO level assessment are needed to confirm the findings of the present study in larger samples on different populations.
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