Table 3.
Subgroup analysis to assess the effect of grape polyphenols supplementation on different biomarkers of oxidative stress levelsa
| Serum enzyme | Number of trials | WMD | 95% CI (upper limit, lower limit) | P value |
|---|---|---|---|---|
| SOD | ||||
| Health status | ||||
| Unhealthy | 4 | < 0.001 | (−0.001, 0.001) | 0.99 |
| Healthy | 4 | 0.450 | (0.23, 0.66)b | < 0.001 |
| Duration of study | ||||
| 10 wk. or more | 4 | 0.085 | (−0.01, 0.18)b | 0.09 |
| lower than 10 wk | 4 | 0.001 | (−0.006, 0.007) | 0.86 |
| Dose of grape polyphenols | ||||
| 400 mg/d or more | 4 | 0.539 | (0.24, 0.82)b | < 0.001 |
| Lower than 400 mg/d | 4 | < 0.001 | (−0.001, 0.001) | 0.75 |
| Type of study | ||||
| Cross-over | 4 | 0.539 | (0.24, 0.82)b | < 0.001 |
| Parallel | 4 | < 0.001 | (−0.001, 0.001) | 0.75 |
| Study quality | ||||
| Good | 4 | 0.085 | (−0.01, 0.18) | 0.08 |
| Fair | 3 | < -0.001 | (−0.001, 0.001) | 0.75 |
| Weak | 1 | 2.399 | (2.01, 2.78)b | < 0.001 |
| TAC | ||||
| Health status | ||||
| Unhealthy | 2 | −0.254 | (−0.65, 0.14) | 0.21 |
| Healthy | 4 | 2.829 | (0.13, 5.52)b | 0.04 |
| Duration of study | ||||
| More than 6 wk | 3 | 3.814 | (−4.14, 11.77) | 0.34 |
| 6 wk. or lower | 3 | 0.084 | (−0.36, 0.52) | 0.71 |
| Dose of grape polyphenols | ||||
| More than 650 mg/d | 2 | −0.058 | (−0.22, 0.11) | 0.49 |
| 650 mg/d or lower | 4 | 2.595 | (−2.53, 7.72) | 0.32 |
| Type of study | ||||
| Cross-over | 3 | 2.785 | (0.01, 5.55)b | 0.04 |
| Parallel | 3 | −0.164 | (−0.65, 0.33) | 0.51 |
| Study quality | ||||
| Good | 3 | −0.145 | (−1.18, −0.10)c | < 0.001 |
| Fair | 2 | 0.266 | (−0.22, 0.75) | 0.28 |
| Weak | 1 | 8.01 | (7.54, 8.49)b | < 0.001 |
| ORAC | ||||
| Health status | ||||
| Abnormal wt.d | 2 | −0.030 | (−0.46, 0.40) | 0.89 |
| Healthy | 3 | 0.524 | (0.42, 0.62)b | < 0.001 |
| Duration of study | ||||
| 10 wk. or more | 2 | 0.543 | (0.43, 0.64)b | < 0.001 |
| Lower than 10 wk | 3 | 0.089 | (−0.26, 0.44) | 0.62 |
| Dose of grape polyphenols | ||||
| More than 400 mg/d | 2 | 0.377 | (0.08, 0.67)b | 0.01 |
| 400 mg/d or lower | 3 | 0.161 | (−0.26, 0.58) | 0.46 |
| Type of study | ||||
| Cross-over | 4 | 0.210 | (−0.15, 0.57) | 0.25 |
| Parallel | 1 | −140.0 | (−651.9, 371.9) | 0.59 |
| Study quality | ||||
| Good | 2 | 0.365 | (0.01, 0.71)b | 0.03 |
| Fair | 2 | − 0.251 | (−0.36, −0.13)c | < 0.001 |
| Weak | 1 | 0.377 | (0.08, 0.67)b | 0.01 |
| MDA | ||||
| Health status | ||||
| Unhealthy | 3 | − 0.092 | (−0.50, 0.32) | 0.66 |
| Healthy | 4 | −0.214 | (−0.62, 0.19) | 0.30 |
| Duration of study | ||||
| 8 wk. or more | 5 | −0.149 | (−0.47, 0.17) | 0.36 |
| Lower than 8 wk. | 2 | 0.096 | (−1.14, 1.33) | 0.88 |
| Dose of grape polyphenols | ||||
| 600 mg/d or more | 4 | −0.237 | (−0.58, 0.11) | 0.18 |
| Lower than 600 mg/d | 3 | −0.034 | (−0.88, 0.81) | 0.93 |
| Type of study | ||||
| Cross-over | 2 | 0.003 | (−0.05, 0.05) | 0.90 |
| Parallel | 5 | −0.328 | (−0.79, 0.14) | 0.17 |
| Study quality | ||||
| Good | 4 | −0.072 | (−0.55, 0.40) | 0.77 |
| Fair | 3 | −0.313 | (−0.67, 0.05) | 0.09 |
| GPX | ||||
| Health status | ||||
| Unhealthy | 2 | 0.009 | (−0.02, 0.04) | 0.60 |
| Healthy | 3 | 0.044 | (−0.03, 0.12) | 0.30 |
| Duration of study | ||||
| More than 10 wk | 3 | −0.002 | (−0.01, 0.01) | 0.83 |
| 10 wk. or lower | 2 | 0.068 | (−0.07, 0.20) | 0.33 |
| Dose of grape polyphenols | ||||
| 400 mg/d or more | 3 | 0.063 | (−0.02, 0.15) | 0.16 |
| Lower than 400 mg/d | 2 | < 0.001 | (−0.001, 0.001) | 0.80 |
| Type of study | ||||
| Cross-over | 3 | 0.063 | (−0.02, 0.15) | 0.16 |
| Parallel | 2 | < 0.001 | (−0.001, 0.001) | 0.80 |
| Study quality | ||||
| Good | 3 | 0.063 | (−0.02, 0.15) | 0.16 |
| Fair | 2 | < 0.001 | (−0.001, 0.001) | 0.80 |
a CI confidence interval, GPX Glutathione Peroxidase, MDA malondialdehyde, ORAC Oxygen Radical Absorbance Capacity, SE standard error, SOD Superoxide Dismutase, TAC Total Antioxidant Capacity, WMD weighted mean difference, wt weight
b Significant increase in the outcome was observed
c Significant decrease in the outcome was observed
d Abnormal weight that is, participants were obese or overweight