Obesity is associated with chronic low-grade inflammation and endothelial dysfunction, which contribute to the development of cardiovascular disease (CVD). Biomarkers of inflammation and endothelial dysfunction in obese individuals may indicate changes in the progression and development of CVD, suggesting a need to focus more on specific foods in the diet which may help to ameliorate inflammatory responses. Habitual nut consumption is associated with decreased risk of CVD and coronary heart disease, although a range of effects have been found in clinical trials exploring the effects of nut intake on markers of inflammation and endothelial function. The aim of this meta-analysis was to evaluate the evidence on the effect of nut consumption on inflammatory biomarkers and endothelial function.
A systematic search of Medline, PubMed, CINAHL and Cochrane Central Register of Controlled Trials (all years to 13 January 2016) was conducted. Inclusion criteria were randomised controlled trials (duration: 3 weeks or longer) or prospective cohort designs with adults; and studies assessing the effect of consumption of tree nuts or peanuts on C-reactive protein (CRP), adiponectin, tumour necrosis factor-alpha, interleukin-6, intercellular adhesion molecule 1, vascular cell adhesion protein 1, and flow mediated dilation (FMD). Random effects meta-analyses were conducted to assess the weighted mean differences in change or final mean values for each outcome.
A total of n=32 studies were included in the review. Consumption of nuts resulted in significant improvements in FMD (WMD: 0.79 [0.35, 1.23]). Non-significant changes in biomarkers of inflammation were found.
This systematic review and meta-analysis found evidence for favourable effects of nut consumption on FMD, a measure of endothelial function. Non-significant changes in other biomarkers indicate a lack of consistent evidence for effects of nut intake on inflammation, highlighting the need for further randomised controlled trials in this area.