Effects of nut consumption on selected inflammatory markers: a systematic review and meta-analysis of randomized controlled trials.

OBJECTIVE

Several randomized controlled trials (RCTs) have assessed the effects of nut consumption on inflammatory markers. However, the results have been inconsistent. The aim of this meta-analysis of RCTs was to quantitatively evaluate the effects of nut consumption on selected inflammatory markers.

METHODS

PubMed, Embase, Cochrane Library database, and Google Scholar were searched for published RCTs that reported the effects of nuts on inflammatory markers as primary or secondary outcomes in an adult population (aged ≥18 y). Summary estimates of weighted mean differences (WMDs) and 95% confidence intervals (CIs) were calculated using random-effects meta-analysis.

RESULTS

Twenty-three RCTs met the inclusion criteria. Overall, nut consumption significantly reduced the levels of intercellular adhesion molecule (ICAM)-1 (WMD, -0.17; 95% CI, -0.32 to -0.03; P = 0.01), but had no significant effect on other inflammatory markers. In the subgroup analyses by nut types, mixed nuts had a significant effect on ICAM-1 reduction. The significant effect of nuts on ICAM-1 reduction was only observed in parallel, but not crossover RCTs. Additionally, nut consumption significantly reduced ICAM-1 and vascular cell adhesion molecule-1 levels in long-term (≥12 wk), but not short-term (<12 wk) RCTs. No significant heterogeneity or publication bias was observed in the studies included.

CONCLUSIONS

Nut consumption significantly reduced ICAM-1 levels, but had no effect on other inflammatory markers. More studies are needed to assess the effects of nuts on inflammation.