CARDIOVASCULAR-RESPONSES TO A HIGH-FAT AND A HIGH-CARBOHYDRATE MEAL IN HEALTHY ELDERLY SUBJECTS

1. The cardiovascular responses to high-fat and high-carbohydrate meals (2.5 MJ) were compared in healthy, non-obese elderly subjects (mean age 68 years, range 63-74 years). 2. Measurements of cardiac output, blood pressure, heart rate, calf blood flow and superior mesenteric artery blood flow were made before and for 60 min after the two meals. 3. Systolic blood pressure only fell after the high-carbohydrate meal, reaching a nadir 13 mmHg below baseline values (95% confidence interval of the change, -2 to -25 mmHg). Diastolic blood pressure fell by 8 mmHg at 30 min after the high-carbohydrate meal (95% confidence interval of the change, -1 to -15 mmHg) and by 5 mmHg 45 min after the high-fat meal (95% confidence interval of the change, -1 to -8 mmHg). 4. Superior mesenteric artery blood flow rose by 70% after the high-carbohydrate meal (95% confidence interval of the change, +105 to +297 ml/min) and by 42% after the high-fat meal (95% confidence interval of the change, +105 +35 to +256 ml/min, P< 0.0001, analysis of variance). Calf blood flow reached a nadir 30 min after the high-carbohydrate meal (95% confidence interval of the change, -0.14 to -0.96 ml min-1 100 ml-1) and 15 min after the high-fat meal (95% confidence interval of the change, -0.1 to -0.92 ml min-1 100 ml-1 P<0.01). There was no significant change in heart rate or cardiac output over the experimental period. 5. In elderly subjects the gut hyperaemia associated with food ingestion is not accompanied by concomitant increases in cardiac output and heart rate. This failure of cardiovascular adjustment to the vascular demands by the gut is likely to contribute to the fall in blood pressure seen in these healthy elderly subjects.