The effects of guar gum supplementation on glycemic control, body mass and blood pressure in adults: A GRADE-assessed systematic review and meta-analysis of randomized clinical trials.

BACKGROUND: This systematic review and meta-analysis sought to evaluate the effects ofguar gum supplementation on glycemic control, blood pressure, and body mass in adults. METHODS: Relevant studies were obtained by searching the PubMed, SCOPUS, Embase, and Web of Science databases (from inception to January 2022). Weighted mean differences (WMD) and 95% confidence intervals (CIs) were pooled using a random-effects model. Heterogeneity, sensitivity analysis, and publication bias were reported using standard methods. RESULTS: Pooled analysis of 14 randomized controlled trials (RCTs) revealed that guar gum supplementation led to significant reductions in hemoglobin A1c (HbA1c) (WMD: -0.47 mg/dL, 95% CI: -0.75, -0.18, p = 0.001). However, there was no effect on fasting blood sugar (FBS), systolic and diastolic blood pressure, and body mass among adults in comparison with the control group. A subgroup analysis demonstrated that intervention in patients with type 2 diabetes (T2DM), and high supplementation dosages (>15 g/d) significantly decreased FBS concentrations, but not in other subgroups. CONCLUSION: Guar gum supplementation may yield a beneficial effect on glycemic control in T2DM patients. However, the extant clinical trials, thus far, are not sufficient enough to form guidelines for clinical practice.

The effects of guar gum supplementation on lipid profile in adults: a GRADE-assessed systematic review, meta-regression and dose-response meta-analysis of randomised placebo-controlled trials.

Recent meta-analytic work indicated that guar gum supplementation might improve lipid profile markers in different populations. However, critical methodological limitations such as the use of some unreliable data and the lack of inclusion of several relevant studies, and the scarcity in assessments of regression and dose-specific effects make it difficult to draw meaningful conclusions from the meta-analysis. Therefore, current evidence regarding the effects of guar gum supplementation on lipid profile remains unclear. The present systematic review, meta-regression and dose-response meta-analysis aimed to examine the effects of guar gum supplementation on lipid profile (total cholesterol (TC), LDL, TAG and HDL) in adults. Relevant studies were obtained by searching the PubMed, SCOPUS, Embase and Web of Science databases (from inception to September 2021). Weighted mean differences (WMD) and 95 % CI were estimated via a random-effects model. Heterogeneity, sensitivity analysis and publication bias were reported using standard methods. Pooled analysis of nineteen randomised controlled trials (RCT) revealed that guar gum supplementation led to significant reductions in TC (WMD: -19·34 mg/dl, 95 % CI -26·18, -12·49, P < 0·001) and LDL (WMD: -16·19 mg/dl, 95 % CI -25·54, -6·83, P = 0·001). However, there was no effect on TAG and HDL among adults in comparison with control group. Our outcomes suggest that guar gum supplementation lowers TC and LDL in adults. Future large RCT on various populations are needed to show further beneficial effects of guar gum supplementation on lipid profile and establish guidelines for clinical practice.

Vitamin C supplementation and C-reactive protein levels: Findings from a systematic review and meta-analysis of clinical trials.

Background and purpose C-reactive protein (CRP) is an inflammatory biomarker which prognosticates cardiovascular disease. Previous studies have reached mixed conclusions regarding the effect of vitamin C on reducing CRP or hs-CRP level. The present systematic review and meta-analysis was conducted to resolve these inconsistencies. Materials and methods: Related articles published up to August 2018 were searched through PubMed, Scopus, Ovid, ISI web of science, Embase, and Cochrane databases by relevant keywords. Clinical trials which examined the effect of either vitamin C supplementation or vitamin C-enriched foods on CRP and hs-CRP levels were included. A total of 11 studies with 14 data sets involving 818 subjects were included. Results Overall, the pooled analysis revealed that vitamin C could decrease CRP level relative to placebo group (Weighted mean difference [WMD]=-0.73 mg/L: 95% CI: -1.30 to -0.15, p=0.013) with a considerable heterogeneity (I2=98%, p<0.001). Moreover, subgroup analyses revealed that the beneficial effect of vitamin C on CRP level alternation only was found in male (p=0.003), non-smoker (p=0.041), healthy (p=0.029) and younger participants (p=0.010). Vitamin C could improve CRP level only at doses of less than 500 mg/day (p=0.009). Regarding hs-CRP changes, the pooled analysis did not show any significant effect of vitamin C (WMD=-0.65 mg/L: 95% CI: -2.03 to 0.72, p=0.35). This finding was confirmed by all subgroup analyses expect for high quality articles in which hs-CRP level was elevated after vitamin C supplementation (p=0.026). Conclusion In conclusion, supplementation with vitamin C might have a significant effect only on CRP reduction. Further studies are needed to confirm this effect.

Effect of l-arginine supplementation on C-reactive protein and other inflammatory biomarkers: A systematic review and meta-analysis of randomized controlled trials.

OBJECTIVES: We carried out a systematic review and meta-analysis of randomized controlled trials (RCTs) to assess the effect of L-arginine on inflammatory biomarkers including C-reactive protein (CRP), interleukin-6 (IL-6) and TNFα. METHODS: A systematic search was carried out in PubMed, Embase, Scopus, Cochrane library databases and ISI web of sciences to retrieve the RCTs which examined the effect of L-arginine supplementation on inflammatory biomarkers up to October 2019, with no language and time restriction. Meta-analysis was performed using a random effects model, and I2 index was used to evaluate the heterogeneity. RESULTS: Search yielded 2452 publications. Eleven RCTs were eligible. Results indicated that L-arginine supplementation had no significant effect on inflammatory biomarkers including CRP, IL-6 and TNFα. However, when subgroup analysis was performed, we found that L-arginine supplementation increased CRP levels in subjects with ages >60 years old, participants with baseline circulating CRP levels >3 mg/dl, patients with cancer and when used in enteral formula. CONCLUSION: Results of the present meta-analysis indicated that L-arginine supplementation increased the circulating concentrations of CRP in subjects with ages >60 years old, subjects with higher levels of CRP, patients with cancer and when used in enteral formula. Therefore, L-arginine should be used with caution in these subjects. However, further well designed, large-scale studies are needed.