The aim of this double-blinded, randomized, placebo-controlled and crossover study was to examine the effects of walnut consumption on cardiovascular risk factors and to explore the underlying mechanisms.

10 obese subjects have been enrolled and participated in two 5-day periods during which they consumed a placebo smoothie or a walnut-containing smoothie (48 g walnuts per day). Walnut consumption reduced fasting small and dense LDL particles (p < 0.02) and increased pastprandial large HDL particles (p < 0.01). Insulin Resistance Score, glucose and insulin AUC decreased significantly after walnut consumption (p < 0.01, p < 0.02, p < 0.04, respectively). Lipidomic analysis showed a robust reduction in harmful ceramides, hexosylceramides and sphingomyelins, which have been shown to mediate effects on cardiometabolic risk. Peptide YY AUC significantly increased after walnut consumption (p < 0.03).

The authors concluded that walnut consumption may reduce cardiovascular risk, at least in part through the reduction of ceramides and other atherogenic lipids.

Tuccinardi D, Farr OM, Upadhyay J, Oussaada SM, Klapa MI, Candela M, Rampelli S, Lehoux S, Lázaro I, Sala-Vila A, Brigidi P, Cummings RD, Mantzoros CS. Mechanisms Underlying the Cardiometabolic Protective Effect of Walnut Consumption in Obese Subjects: A Cross-Over, Randomized, Double-Blinded, Controlled Inpatient Physiology Study. Diabetes Obes Metab. 2019 May 14.