It is generally well-known that including walnuts in your diet will have positive effects on the vascular function. However, the reasons for this effect were previously unknown. In 2015, a research team from California investigated the acute and short-term effects of the consumption of walnuts on the microvascular function. They suspected a connection with a value in the blood plasma, Cytochrome P 450. This is an endogenous enzyme which is primarily found in the liver and is responsible for the metabolic process of fatty acids. 38 women beyond menopause, all with increased cholesterol levels, were used as test subjects for this study. They were randomly assigned to two different groups. Over a period of four weeks, the first group was given 5 g of walnuts per day while the second group received 40 g. The vessel function, cholesterol levels and the level of Cytochrome P 450 was then measured each morning and again four hours after walnut consumption. Compared with those easting 5 g of walnuts, the group consuming 40 g of walnuts showed a more positive microvascular function. In addition, the Cytochrome P 450 level increased throughout the four-week study. The cholesterol levels did not change significantly. The available data therefore supports the fact that the consumption of fatty acids from walnuts has a positive effect on the production of those enzymes which are required for the fat metabolism. This effect in turn suggests an improvement in vessel function.
Holt RR. et al.: Effects of short-term walnut consumption on human microvascular function and its relationship to plasma epoxide content. J Nutr Biochem, Aug 2015