The effects of flaxseed (Linum usitatissimum) supplementation on anthropometric indices: An updated systematic review and meta-analysis of randomized clinical trials.

OBJECTIVE: Flaxseed (Linum usitatissimum) supplementation has shown promise as an anti-obesity agent in various clinical trials, although results have been inconsistent. To provide a more accurate assessment of the impact of flaxseed supplementation on anthropometric indices, a systematic review and meta-analysis was performed. METHODS: We searched several international databases until August 2023, including Scopus, PubMed, Web of Science, Embase, and Cochrane Library. Weighted mean differences (WMDs) were analyzed using a random-effects model. RESULTS: Sixty-four trials comprising 72 treatment arms were included. All studies reported the intervention types (Lignans, Whole flaxseed, and Flaxseed oil) and dosage. However, three studies did testing for purity, and 40 studies reported potency. Also, the risk of contamination with heavy metals was not mentioned in studies. Another limitation was the lack of blind evaluation in the studies. According to three trials included in the systematic review, flaxseed did not affect anthropometric indices. Our meta-analysis revealed significant reductions in body weight (WMD = -0.63 kg; 95 % CI: -1.00, -0.27, P < 0.001; I2 = 76.7 %, P < 0.001), body mass index (BMI) (WMD: -0.24 kg/m2, 95 % CI: -0.36, -0.11, P < 0.001; I2 = 78.5 %, P < 0.001) and waist circumference (WC) (WMD: -1.43 cm, 95 % CI: -2.06, -0.80, P < 0.001; I2 = 81.1 %, P < 0.001) following flaxseed supplementation. Subgroup analyses indicated that interventions lasting 10-20 weeks, and studies involving subjects with higher BMI (>30 kg/m2) showed more significant anti-obesity effects. Based on the GRADE evaluation, body weight, BMI, and WC results were considered as moderate-certainty evidence. CONCLUSION: Our systematic review and meta-analysis suggests that supplementation with flaxseed (Linum usitatissimum) leads to meaningful improvements in body weight, BMI, and WC. Therefore, flaxseed can be considered as an adjunctive therapeutic approach in improving obesity.

A high dietary acid load can potentially exacerbate cardiometabolic risk factors: An updated systematic review and meta-analysis of observational studies.

AIMS: Chronic metabolic acidosis has been shown to be associated with cardiometabolic risk factors. The aim of the currently updated meta-analysis was to explore the association between Potential Renal Acid Load (PRAL) and Net Endogenous Acid Production (NEAP) with these risk factors. DATA SYNTHESIS: Databases were searched up to May 2023. The mean of waist circumference (WC), body mass index (BMI), high- and low-density lipoprotein-cholesterol (HDL-C and LDL-C), triglyceride (TG), total cholesterol (TC), fasting blood sugar (FBS), and systolic- and diastolic blood pressure (SBP and DBP) in highest category vs lowest categories of NEAP and PRAL were recorded. Effect sizes were generated as weighted mean difference (WMD). Results showed that SBP, DBP, and WC had a significant difference in the upper and lower categories of PRAL (WMDSBP: 1.466 mmHg; 95% CI: 2.121, -0.811; P<0.001, WMDDBP: 0.710 mmHg; 95 % CI: 1.170, -0.249; P=0.003, and WMDWC: 0.819 cm; 95% CI: 1.446, -0.192; P=0.010) or NEAP (WMDSBP: 1.690 mmHg; 95% CI: 2.789, -0.591; P=0.003, WMDDBP: 1.076 mmHg, and WMDWC: 1.325 cm; 95% CI: 1.901, -0.749; P<0.001; 95% CI: 1.938, -0.214; P =0.014). The lowest versus highest categories of dietary PRAL were associated with lower BMI (WMDPRAL: 0.297 kg/m2; 95 % CI: 0.440, -0.154; P<0.001) and TG (WMD: 2.280 mg/dl; 95%CI: 3.828, -0.732; P=0.004; I2=99.4 %; P<0.001). CONCLUSIONS: High DAL can be considered as an independent risk factor for increasing anthropometric indices, blood pressure, and TG. This study registered in the PROSPERO database (Registration No. CRD42023402985).

The effect of cinnamon supplementation on glycemic control in patients with type 2 diabetes mellitus: An updated systematic review and dose-response meta-analysis of randomized controlled trials.

Although many randomized controlled trials (RCTs) have revealed the benefits of cinnamon on type 2 diabetes mellitus (T2DM), the effects of cinnamon supplementation on glycemic control in patients with T2DM are inconclusive. Therefore, the aim of this meta-analysis of RCTs was to assess the effects of cinnamon supplementation in managing glycemic control in patients with T2DM. Scientific international databases including Scopus, Web of Sciences, PubMed, Embase, and the Cochrane Library were searched till December 2022. For net changes in glycemic control, standard mean differences (SMDs) were calculated using random-effects models. Findings from 24 RCTs revealed that cinnamon supplementation had a statistically significant reduction in fasting blood sugar (SMD: -1.32; 95% CI: -1.77, -0.87, p < 0.001), Homeostatic Model Assessment for Insulin Resistance (SMD: -1.32; 95% CI: -1.77, -0.87, p < 0.001), and hemoglobin A1C (SMD: -0.67; 95% CI: -1.18, -0.15, p = 0.011) compared with the control group in patients with T2DM. Additionally, cinnamon did not change the serum levels of insulin (SMD: -0.17; 95% CI: -0.34, 0.01, p = 0.058) significantly. Our analysis indicated that glycemic control indicators are significantly decreased by cinnamon supplementation. Together, these findings support the notion that cinnamon supplementation might have clinical potential as an adjunct therapy for managing T2DM.

The effect of curcumin supplementation on circulating adiponectin and leptin concentration in adults: a GRADE-assessed systematic review and meta-analysis of randomised controlled trials.

Curcumin is a phytocompound found in the root of turmeric, a common herbal ingredient in many Asian cuisines. The compound contains anti-inflammatory activity, which is mediated through an upregulation of adiponectin and reduction of leptin. Results of randomised controlled trials (RCT) have shown that the effects of curcumin on adipokines are conflicting. Therefore, the current systematic review and meta-analysis of RCT were conducted with the aim of elucidating the role of curcumin supplementation on serum adiponectin and leptin. The search included PubMed, Embase, Cochrane Library, Scopus, Web of Science and Google Scholar from inception to August 2023. For net changes in adipokines, standardised mean differences (SMD) were calculated using random effects models. Thirteen RCT with fourteen treatment arms were eligible for inclusion in this meta-analysis. Curcumin supplementation was effective in increasing serum adiponectin (SMD = 0·86, 95 % CI (0·33, 1·39), P < 0·001; I2 = 93·1 %, P < 0·001) and reducing serum leptin (SMD = -1·42, 95 % CI (-2·29, -0·54), P < 0·001; I2 = 94·7 %, P < 0·001). In conclusion, curcumin supplementation significantly increased circulating adiponectin and decreased leptin levels in adults.

The effect of flaxseed supplementation on sex hormone profile in adults: a systematic review and meta-analysis.

Inconsistent data suggest that flaxseed supplementation may have a role in sex hormones. We aimed to carry out a systematic review and meta-analysis of randomized controlled trials (RCTs) investigating effects of flaxseed supplementation on sex hormone profile. PubMed, Scopus, Embase, Cochrane Library, Web of Science databases, and Google Scholar were searched up to March 2023. Standardized mean difference (SMD) was pooled using a random-effects model. Sensitivity analysis, heterogeneity, and publication bias were reported using standard methods. The quality of each study was evaluated with the revised Cochrane risk-of-bias tool for randomized trials, known as RoB 2. Finding from ten RCTs revealed that flaxseed supplementation had no significant alteration in follicle-stimulating hormone (FSH) (SMD: -0.11; 95% CI: -0.87, 0.66: p = 0.783), sex hormone-binding globulin (SHBG) (SMD: 0.35; 95% CI: -0.02, 0.72; p = 0.063), total testosterone (TT) levels (SMD: 0.17; 95% CI: -0.07, 0.41; p = 0.165), free androgen index (FAI) (SMD = 0.11, 95% CI: -0.61, 0.83; p = 0.759), and dehydroepiandrosterone sulfate (DHEAS) (SMD: 0.08, 95%CI: -0.55, 0.72, p = 0.794). Flaxseed supplementation had no significant effect on sex hormones in adults. Nevertheless, due to the limited included trials, this topic is still open and needs further studies in future RCTs.

The effects of purslane (Portulaca oleracea) on glycemic indices: A GRADE-assessed systematic review and meta-analysis of randomized controlled trials.

Although several studies have revealed the benefits of purslane on glycemic indices, the results of some studies reject such effect. Therefore, aim of this meta-analysis of randomized controlled trials (RCTs) was to assess the effects of purslane supplementation on glycemic indices. Scientific international databases as Scopus, Web of Sciences, PubMed, Embase, and the Cochrane library were searched up to December 2022. For net changes in glycemic indices, weighted mean differences (WMDs) were calculated using random-effects models. Purslane supplementation had a statistically significant reduction in fasting blood glucose [FBG, WMD: -6.37; 95% CI: -9.34, -3.40, p < 0.001]. In addition, purslane did not significant effect on serum levels of insulin [WMD: -0.74; 95% CI: -2.58, 1.10; p = 0.430], homeostasis model assessment for insulin resistance [HOMA-IR, WMD: -0.25; 95% CI: -0.88, 0.37, p = 0.429], and QUICKI [WMD: -0.01; 95% CI: -0.01, 0.03, p = 0.317] compared with the control group. The results of our meta-analysis revealed a beneficial effect of purslane supplementation as a tool to decrease FBG levels, but not to HOMA-IR, insulin, and QUICKI levels. However, future high-quality, long-term clinical trials are needed to confirm our results.

The effect of Nigella sativa (black seed) on biomarkers of inflammation and oxidative stress: an updated systematic review and meta-analysis of randomized controlled trials.

OBJECTIVE: This study was conducted to assess the effect of Nigella sativa (N. sativa) supplementation on inflammatory and oxidative markers among the adult population. METHODS: We carried out a comprehensive, systematic search of Scopus, Embase, Cochrane Library, Web of Science, PubMed, and Google Scholar till December 2022. A random-effects model was used to estimate the overall effect size. RESULTS: In total, twenty trials consisting of 1086 participants were included in the meta-analysis. Findings from 20 RCTs included in the meta-analysis suggest that N. sativa supplementation could significantly reduce serum C-reactive protein (CRP) (SMD = - 2.28; 95% CI - 3.20, - 1.37, p < 0.001), tumour necrosis factor α (TNFα) (SMD = - 1.21; 95% CI - 2.15, - 0.26; p = 0.013), and malondialdehyde (MDA) (SMD = - 2.15; 95% CI - 3.37, - 0.93, p < 0.001) levels, and significantly improves total antioxidant capacity (TAC) (SMD = 2.28; 95% CI 1.29, 3.27, p < 0.001), glutathione peroxidase (GPx) (SMD = 1.23, 95% CI 0.25, 2.22; p = 0.014) and superoxide dismutase (SOD) (SMD = 2.05; 95% CI 1.22, 2.88, p < 0.001) levels. However, no significant reduction was found in interleukin 6 (IL-6) levels (SMD = - 1.13; 95% CI - 2.72, 0.46, p = 0.162). CONCLUSION: N. sativa supplementation had beneficial effects on CRP, TNF-α, MDA, SOD, GPx, and TAC. Thus, Nigella sativa can be recommended as an adjuvant anti-oxidant agent and anti-inflammatory.

Profiling Inflammatory Biomarkers following Curcumin Supplementation: An Umbrella Meta-Analysis of Randomized Clinical Trials.

Objective: Several meta-analyses have shown that curcumin can reduce inflammatory biomarkers, but the findings are inconsistent. The objective of the present umbrella meta-analysis was to provide a more accurate estimate of the overall effects of curcumin on inflammatory biomarkers. Methods: The following international databases were systematically searched until March 20, 2022: PubMed, Scopus, Embase, Web of Science, and Google Scholar. A random-effects model was applied to evaluate the effects of curcumin on inflammatory biomarkers. Meta-analysis studies investigating the effects of curcumin supplementation on inflammatory biomarkers with corresponding effect sizes (ES) and confidence intervals (CI) were included in the umbrella meta-analysis. GRADE (Grading of Recommendations Assessment, Development, and Evaluation) was used to evaluate the certainty of evidence. Results: A meta-analyses of ten studies with 5,870 participants indicated a significant decrease in C-reactive protein (CRP) (ES = -0.74; 95% CI: -1.11, -0.37, p < 0.001; I2 = 62.1%, p=0.015), interleukin 6 (IL-6) (ES = -1.07; 95% CI: -1.71, -0.44, p < 0.001; I2 = 75.6%, p < 0.001), and tumour necrosis factor α (TNF-α) levels (ES: -1.92, 95% CI: -2.64, -1.19, p < 0.0; I2 = 18.1%, p=0.296) following curcumin supplementation. Greater effects on CRP and TNF-α were evident in trials with a mean age >45 years and a sample size >300 participants. Conclusion: The umbrella of meta-analysis suggests curcumin as a promising agent in reducing inflammation as an adjunctive therapeutic approach in diseases whose pathogenesis is related to a higher level of inflammatory biomarkers.

Validity and reliability of a semi-quantitative food frequency questionnaire for assessing dietary vitamin D and calcium intakes in Iranian childbearing age women.

This study aimed to examine the validity and reliability of a semi-quantitative food frequency questionnaire (FFQ) designed to estimate dietary vitamin D and Calcium (Ca) intakes in a sample of Iranian childbearing age women. An 87-item FFQ was developed and 84 healthy childbearing age women completed it. FFQ was validated by comparing its results with the 24-h dietary recall (24-h recall) and serum 25-hydroxyvitamin D (S-25(OH)D) as the references methods. The FFQ was completed for the second time after 4 weeks to assess the reliability of the questionnaire. Data were analyzed using spearman's correlation, cross-classification analysis, Bland-Altman plots, the weighted κ, intraclass classification, and the method of triads. Spearman's correlations between vitamin D and Ca intakes by the FFQ and 24-h recalls and between vitamin D intakes and S-25(OH)D were significant (r: 0.706, r: 0.959, and r: 0.682, respectively, all, P < 0.001). Cross-classification for vitamin D and Ca between two dietary methods and for vitamin D intake of FFQ and S-25(OH)D demonstrated that most of the quartiles were categorized into the same or adjacent quartiles. The Bland Altman plots for these nutrients also demonstrated good agreement. For vitamin D, the validity coefficients (VCs) calculated by the method of the triad for three methods were in the range of 0.808-0.843. The weighted κ for agreement of vitamin D and Ca by FFQ1 and FFQ2 were 0.18 and 0.638, respectively. The findings indicated that the developed FFQ has acceptable validity for estimating vitamin D and Ca. Its reliability for Ca was stronger than vitamin D.