Effects of meals on hemodynamics: implications for antihypertensive drug studies.

The ingestion of food is known to affect blood pressure and heart rate, but food is often allowed in patients under observation for antihypertensive drug effects. Seventy-seven patients with essential hypertension were observed for 8 hours after a 16-hour fast. Thirty-six continued to fast, 20 ate a high-carbohydrate meal, and 21 ate a meal of their own choice. Blood pressure and heart rate did not change during fasting, but both meals lowered mean supine and standing diastolic blood pressures during the subsequent 4 hours by 3 to 7 mm Hg (P less than 0.001). The high-carbohydrate meal reduced supine systolic blood pressure by 6 mm Hg (P less than 0.0001). Both meals increased supine and standing heart rates by 5 to 8 bpm (P less than 0.001). After the self-selected meal, standing systolic blood pressure increased in younger patients but decreased in older patients. Food ingestion during antihypertensive drug studies may interfere with the interpretation of results and should be avoided whenever possible.