The effect of soya consumption on inflammatory biomarkers: a systematic review and meta-analysis of clinical trials

Abstract

Inflammation is a major cause of chronic diseases. Several studies have investigated the effects of soy intake on inflammatory biomarkers; however, the results are equivocal. The aim of this study was to conduct a systematic review and meta-analysis of clinical trials that evaluated the effect of soy consumption on inflammatory biomarkers. Medline, Scopus, ISI Web of Science, and Google Scholar were systematically searched, up to and including May 2020, for clinical trials that evaluated the effects of soy and soy products on tumor necrosis factor α (TNF-α), Interleukin-6 (IL-6), Interleukin-2 (IL-2), Interleukin1-β (IL1-β), and Interferon gamma (IFN-γ) in adults. A random-effects method was used to calculate overall effects, and subgroup analyses were performed to discern probable sources of inter-study heterogeneity. A total of 28 clinical trials were included. Although soy consumption reduced TNF-α (Hedges’ g= −0.28; 95%CI: −0.49, −0.07), it had no significant effect on IL-6 (Hedges’ g= 0.07, 95% CI: −0.14, 0.28), IL-2 (MD= −1.38 pg/ml; 95%CI: −3.07, 0.31), IL1-β (MD= −0.02 pg/ml; 95%CI: −0.08, 0.03), and IFN-γ (MD= 1685.82 pg/ml; 95%CI: −1604.86, 4976.50). Subgroup analysis illustrated a reduction in TNF-α in in parallel designed studies, at dosages ≥100 mg of isoflavones, and in unhealthy subjects. The present study showed that high doses of isoflavones in unhealthy subjects may yield beneficial effects on TNF-α.

Effects of whey and soy protein supplementation on inflammatory cytokines in older adults: a systematic review and meta-analysis

“…Additionally, experimental studies have not observed a significant effect of soy food consumption on serum CRP levels (74) that may be attributed to the interaction of multiple nutrients contained in whole soy foods (75) compared with isolated sources (76) . Our analysis revealed a significant effect of soy protein supplementation in reducing serum TNF-α levels, which are in line with previous research (77,78) , although, insignificant reductions of serum IL-6 levels were displayed as reported previously (23) . Furthermore, subgroup analysis showed that the addition of isoflavones did not decrease serum CRP and IL-6 levels; however a significant reduction of serum TNF-α was observed.…”

Effect of the Fermented Soy Q-CAN® Product on Biomarkers of Inflammation and Oxidation in Adults with Cardiovascular Risk, and Canonical Correlations between the Inflammation Biomarkers and Blood Lipids

“…Findings from previous randomized controlled trials with soy foods and isoflavone supplements are inconsistent reporting increased [ 20 , 37 ], decreased [ 13 , 14 ], or no change [ 20 , 21 ] in concentrations of IL-6. Although soy food consumption was shown to inhibit IL-6 and TNF-α in a population study [ 10 ], results from recent meta-analyses and reviews of clinical trials examining the effect of soy intake on inflammation are inconclusive and show modest or no beneficial effects of soy intake in mitigating one or more of the cytokines or inflammatory indicators [ 38 , 39 , 40 ]. Although it is unclear why IL-6 levels increased in participants consuming the fermented soy powder, the causes may be due either to participant characteristics or the soy supplement dose.…”

“…It is well-known that isoflavones as estrogens mimetics may exert pseudo-hormonal activity by binding to estrogen receptors in females [ 43 ]. Although some clinical trials of soy foods among women have shown reductions in TNF-α levels [ 12 , 17 ], findings from recent meta-analysis studies have been inconsistent [ 38 , 40 ]. One subgroup analysis of clinical trials reported that inhibition of TNF-α generally occurred in studies utilizing lower doses of isoflavones [ 31 ].…”