['It has been suggested that an oxidative mechanism is involved with the impaired endothelium-dependent vasodilatation that occurs after a high-fat meal.', 'The study was undertaken to evaluate the effect of a single oral dose of vitamin C (2 g) on postprandially impaired endothelium-dependent vasodilatation in patients with coronary heart disease (CHD).', 'This study included 74 patients with CHD and 50 subjects without CHD with risk factors. The two groups were divided into two subgroups that did or did not receive 2 g of vitamin C (CHD/VitC and CHD/control, n = 37; non-CHD/VitC and non-CHD/control, n = 25) after a high-fat meal (800 calories, 50 g fat). Serum levels of triglyceride, total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol in the fasting state and at 2, 4, 5, and 7 h after the high-fat meal were measured. Endothelial function was assessed in the brachial artery by high-resolution ultrasound at baseline and at 4 h postprandially.', 'The postprandial serum triglyceride concentration increased significantly at 2-5 h after the high-fat meal in all groups. The fasting flow-mediated dilatation (FMD) (p < 0.02) and nitroglycerin-induced dilatation (NID) (p < 0.05) of patients with CHD were impaired compared with those of non-CHD subjects. Postprandial FMD was significantly aggravated in the non-CHD/control group (p < 0.01) and the CHD/control group (p < 0.001), but the postprandial FMD in patients and subjects taking vitamin C showed no significant change, although the CHD/VitC group had a mild tendency toward improvement (p = 0.064) and non-CHD/VitC group had a mild tendency toward aggravation (p = 0.852). The change of NID after a high-fat meal did not reach statistical significance in the four groups. The decrement of postprandial FMD correlated positively with the increment of 2-h serum triglyceride concentration in the patients without vitamin C (n = 62, r = 0.545, p < 0.001).'] Does vitamin C preserve endothelial function in patients with coronary heart disease after a high-fat meal?