Grape seed extract reduces blood levels of glucose, lipids and inflammatory C-reactive protein, meta-analysis shows
- Meta-analysis of 15 RCTs with 825 participants (healthy and unhealthy)
- Grape seed extract reduces blood levels of glucose, lipids and inflammatory CRP
- Dosages range from 100 mg/day to 2 g/day for 4 to 25 weeks
This meta-analysis was performed to evaluate the effects of grape seed extract (GSE) on glycemic control and serum lipoproteins, inflammation and body weight.
A systematic literature search was conducted up to May 30, 2019 using online databases (e.g., EMBASE, Scopus, PubMed, Cochrane Library, Web of Science) to identify eligible studies. Inclusion criteria included only high-quality randomized, controlled trials (RCTs), either crossover or parallel, with sufficient data on the effects of GSE on glycemic control, serum lipoproteins, C-reactive protein (CRP) and anthropometric measurements.
Weighted Mean Difference (WMD) was used to evaluate changes in parameters using a random-effects model. Assessments of heterogeneity, publication bias and subgroups were performed.
Fifteen trials with 825 subjects (451 intervention; 374 control) met the inclusion criteria and were included in the meta-analysis. Mean age of participants was between 20 to 64 years. Mean BMI was between 21 and 37 kg/m2. The duration of trials ranged from 4 and 25 weeks. GSE dosage ranged from 100 mg/day and 2 g/day.
Overall, results indicate GSE supplementation significantly improved several blood parameters of metabolic and cardiovascular health. Weighted mean differences (WMD) and 95% confidence intervals (CI) include:
- Fasting glucose: WMD: -2.01 mg/dL (95% CI: -3.14 to -0.86)
- Total Cholesterol: WMD: -6.03 mg/dL (95% CI: -9.71 to -2.35)
- LDL Cholesterol: WMD: -4.97 mg/dL (95% CI: -8.37 to -1.57)
- Triglycerides: WMD: -6.55 mg/dL (95% CI: -9.28 to -3.83)
- CRP: WMD: -0.81 mg/L (95% CI: -1.25 to -0.38)
By contrast, GSE supplementation failed to influence glycated hemoglobin (HbA1c) or HDL cholesterol levels, or anthropometric measurements.
Where the number of studies was adequate, subgroup analyses were performed based on baseline fasting glucose, study length, GSE dosage, health status, study design and BMI. In general, unhealthy individuals benefited the most from GSE supplementation.
These findings indicate that GSE supplementation may offer therapeutic value for the control of blood glucose, blood lipids and inflammatory CRP, especially in people who are unhealthy.