The effect of nut consumption on markers of inflammation and endothelial function: a systematic review and meta-analysis of randomised controlled trials

Abstract

ObjectivesTo examine the effect of nut consumption on inflammatory biomarkers and endothelial function.DesignA systematic review and meta-analysis.Data sourcesMEDLINE, PubMed, Cumulative Index to Nursing and Allied Health Literature and Cochrane Central Register of Controlled Trials (all years to 13 January 2017).Eligibility criteriaRandomised controlled trials (with a duration of 3 weeks or more) or prospective cohort designs conducted in adults; 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).Data extraction and analysisRelevant data were extracted for summary tables and analyses by two independent researchers. Random effects meta-analyses were conducted to explore weighted mean differences (WMD) in change or final mean values for each outcome.ResultsA total of 32 studies (all randomised controlled trials) were included in the review. The effect of nut consumption on FMD was explored in nine strata from eight studies (involving 652 participants), with consumption of nuts resulting in significant improvements in FMD (WMD: 0.79%(95% CI 0.35 to 1.23)). Nut consumption resulted in small, non-significant differences in CRP (WMD: −0.01 mg/L (95% CI −0.06 to 0.03)) (26 strata from 25 studies), although sensitivity analyses suggest results for CRP may have been influenced by two individual studies. Small, non-significant differences were also found for other biomarkers of inflammation.ConclusionsThis systematic review and meta-analysis of the effects of nut consumption on inflammation and endothelial function found evidence for favourable effects on FMD, a measure of endothelial function. Non-significant changes in other biomarkers indicate a lack of consistent evidence for effects of nut consumption on inflammation. The findings of this analysis suggest a need for more research in this area, with a particular focus on randomised controlled trials.PROSPERO registration number CRD42016045424.

Effect of a 12-Week Almond-Enriched Diet on Biomarkers of Cognitive Performance, Mood, and Cardiometabolic Health in Older Overweight Adults

“…The inclusion of almonds in the diet improves aspects of cardiometabolic health without affecting cognitive performance or mood in overweight/obese adults.Nutrients 2020, 12, 1180 2 of 18 cognitive performance [7]. Nut consumption represents one aspect of nutrition with wide ranging benefits that may counteract these negative influences, including reducing oxidative damage and inflammation, and improving vascular responsiveness [8][9][10]. Improvements in vascular function associated with nut intake are proposed to not only improve cardiovascular health but also contribute to improving cognitive function [11].…”

“…Improvements in vascular function associated with nut intake are proposed to not only improve cardiovascular health but also contribute to improving cognitive function [11]. Clinical trials have found improvements in vascular health following consumption of walnuts [12], hazelnuts [13], and almonds [14], but this has not been a consistent finding in all studies, possibly due to differences in methods of assessing vascular health, differences in populations evaluated, dose, or length of the period of consumption [9,10].Furthermore, there is now emerging literature to support nut consumption being associated with enhanced cognitive function or reduced cognitive decline [15,16]. Key nutrients found in nuts (and almonds in particular), including monounsaturated fat [17] and vitamin E [18] have been associated with reduced cognitive decline, and it has been proposed that regular nut consumption may prevent or slow the progressing of age-related brain dysfunction [16,19].…”

“…Improvements in vascular function associated with nut intake are proposed to not only improve cardiovascular health but also contribute to improving cognitive function [11]. Clinical trials have found improvements in vascular health following consumption of walnuts [12], hazelnuts [13], and almonds [14], but this has not been a consistent finding in all studies, possibly due to differences in methods of assessing vascular health, differences in populations evaluated, dose, or length of the period of consumption [9,10].…”

Inflammation as a mediator of arterial ageing

“…Curcumin, a polyphenol found in turmeric, improves both resistance and conduit artery EDD in older adults independent of changes in systemic CRP, IL-6 or TNF- (Santos-Parker et al, 2017a). Flaxseed and nut consumption appear to improve arterial function and reduce inflammation in middle-aged cohorts with cardiovascular and metabolic diseases (Khandouzi, Zahedmehr, Mohammadzadeh, Sanati, & Nasrollahzadeh, 2019;Neale, Tapsell, Guan, & Batterham, 2017).…”

Generating the evidence for risk reduction: a contribution to the future of food-based dietary guidelines

“…Other meta-analyses reported no effect on HDL-C, TAG, FG or body weight (84,85) . Meta-analyses investigating the effects of nut consumption reported reductions in TC, LDL-C, TAG, diastolic blood pressure, FG and glycosylated Hb (both in T2D patients) (86)(87)(88) , but no effects on body weight, HDL-C, SBP and C-reactive protein (87,89,90) . Focusing on legumes, one meta-analysis of ten RCT indicated that interventions to increase the intake of legumes were associated with decreased TC and LDL-C levels compared with a control group (91) , others reported reductions in C-reactive protein, SBP and FG (92,93) , but no effects on body weight (92) .…”