Eating a handful of walnuts can reverse the endothelial dysfunction caused by consuming a high-fat meal, Spanish research shows.
The scientists warn, however, that people should not think it beneficial to continue to eat unhealthy fats, providing that they add walnuts to their diet.
Instead, people should consider replacing unhealthier options with walnuts as a part of a healthy lifestyle that limits their intake of saturated fat.
Previously, Berenice Cortes, from the University of Barcelona, and team had demonstrated that eating walnuts regularly for a month helped improve endothelial dysfunction, but in their current study, they show that just one walnut serving may offer beneficial results.
In a randomized crossover trial, they tested what happened when participants ate two high-fat meals, 1 week apart, supplemented with either 25 g of olive oil or 40 g of walnuts. The high-fat meals consisted of 80 g fat and 35% saturated fatty acids.
Flow-mediated dilation decreased by 36% in patients who ate the olive oil-supplemented meal but remained unchanged in those who ate the meal supplemented with walnuts.
The team says that this may be because olive oil intake increases the presence of large triglyceride-rich very-low-density lipoprotein (VLDL) particles that are highly atherogenic.
"Olive oil does have some beneficial effects – it is not bad, but walnuts are better," explains Emilio Ros, the corresponding author.
Lipid profiles assessments showed that levels of oxidized LDL particles decreased after both meals, independent of the supplement used.
Cortes et al say in the Journal of the American College of Cardiology that this is due to the anti-oxidant content of olive oil and walnuts and demonstrates that, "in spite of a high poly-unsaturated fatty acid content, walnut intake does not promote lipid perioxidation."
Levels of soluble inflammatory cytokines and adhesion molecules also decreased after eating both meals. But adhesion molecule E-selectin levels were lower after participants ate the meal supplemented with walnuts.
Ros concludes that while eating walnut oil could be beneficial, eating the nuts themselves is probably a better option, and even more so if eaten raw.
Free abstract
