Daily consumption of 56 grams of walnuts for 8 weeks significantly improves flow-mediated dilation by 34% and reduces soluble vascular cell adhesion molecule-1 levels in overweight adults with metabolic syndrome, indicating enhanced endothelial function and reduced vascular inflammation without weight gain.

Walnuts provide fatty acids and antioxidants that get incorporated into the lining of blood vessels, making the membranes more flexible and less damaged by harmful molecules. This allows the blood vessels to produce more nitric oxide, which opens them up to improve blood flow. At the same time, the antioxidants stop harmful molecules from attacking the vessel lining, which reduces the signals that attract immune cells and cause swelling.