Findings from the meta-analysis:
Twelve studies with seventeen effect sizes evaluated soy isoflavones
effects on serum CRP concentrations (Figure 2 ). The overall
effect suggested a non-significant effect in serum CRP concentrations
after supplementation with soy isoflavones compared with comparison
group (WMD= 0.08 mg/L, 95% CI: -0.08, 0.24; p=0.302). There was a
substantial heterogeneity between studies (Cochrane’s Q test, p
< 0.001; I2= 87.0%). Sensitivity analysis
showed that excluding each trials from the overall analysis did not
reveal a significant change in overall effect size of soy isoflavones on
CRP concentration. Subgroup analysis based on all studied variables
could not diminish the heterogeneity between studies (Table 3 ).
Subgroup analyses revealed no significant change in circulatory levels
of CRP following soy isoflavones intake compared with comparison group
in any of the subgroups.
The overall effect of soy isoflavones plus soy protein on serum CRP is
shown in Figure 3 . Eleven studies with sixteen effect sizes
assessed the effect of soy protein and soy isoflavones combination on
serum CRP levels. The overall estimates indicated non-significant effect
in serum levels of CRP following soy isoflavones plus soy protein intake
in comparison with control group (WMD= -0.02 mg/L 95% CI: -0.12, 0.08;
p=0.715) with high heterogeneity (Cochrane’s Q test, p <0.001,
I2= 84.9%). Sensitivity analysis showed that
excluding each trials from the overall analysis did not reveal a
significant change in overall effect size of soy isoflavones plus soy
protein on CRP concentration. The between-group heterogeneity was not
significant in trials using soy isoflavones >100 mg/d
(Cochrane’s Q test, p=0.600, I2=0.00%), in trials
with parallel design (Cochrane’s Q test, p=0.074,
I2=53.7%), in trials performed with study
duration>56 day (Cochrane’s Q test, p=0.074,
I2=47.9%) and in trials conducted in healthy people
(Cochrane’s Q test, p=0.330, I2=13.2) (Table
4 ). In subgroup analysis based on BMI indicated that soy isoflavones
plus soy protein could increase CRP levels in people with BMI≤26 (WMD=
0.36 mg/L 95% CI: 0.01, 0.72; p=0.045, I2=65.8%),
but a non-significant reduction was observed in people with
BMI>26 (WMD= -0.08 mg/L 95% CI: -0.18, 0.02; p=0.121,
I2=91.3%) (Figure 4 ). However, in subgroup
analysis revealed no significant change in circulatory levels of CRP
following soy isoflavones plus soy protein intake compared with
comparison group in other subgroups (Table 4 ).