The types of circulating fatty acids influence vascular reactivity.

The objective of this study was to investigate the relationship between the composition of FA in serum lipids, a marker of dietary fat intake, and vascular reactivity using a combination of cross-sectional and intervention approaches. Fifty-six middle-aged subjects were evaluated in a cross-sectional protocol regarding the relationship between the proportion of FA in serum cholesterol esters and vascular reactivity using measurements of forearm blood flow (FBF) with venous occlusion plethysmography during hyperemia. Another 19 middle-aged subjects were given a rapeseed oil-based diet rich in mono- and polyunsaturated FA or a control diet rich in saturated FA during two consecutive 4-wk periods separated by a 4-wk washout period. In the cross-sectional protocol, the FA 18:0 and 20:3 were positively related to resting FBF, whereas an inverse relationship was seen for the FA 20:5 and 22:6 (P < 0.05-0.01). Opposite relationships were seen between these four FA and the relative increase in maximal FBF during hyperemia (P < 0.05-0.01). In the intervention protocol, the saturated diet increased resting FBF, as well as the relative increase in maximal FBF during reactive hyperemia, compared to the diet rich in unsaturated FA (P < 0.05). Both the cross-sectional and intervention data support the view that the composition of serum FA, which at least partly reflects the quality of dietary fat, plays a role in determinations of vascular reactivity.