Acute effects of whey protein, alone and mixed with other macronutrients, on blood pressure and heart rate in older men

Background: Caloric supplements are increasingly used by older people, aiming to increase daily protein intake. These high caloric drinks, rich in glucose and whey-protein in particular, may result in potential harmful decreases in blood pressure (BP). The effect of ingesting whey-protein with glucose and fat is unknown. It has been assumed that the maximum fall in systolic blood pressure occurs within 2 hours of a meal.

Methods: This study aimed to determine the effects of whey-protein, alone and mixed with other macronutrients, on systolic (SBP) and diastolic (DBP) blood pressure and heart rate (HR) in older men for 3 hours. Thirteen older men (age 75±2yrs; body mass index (BMI) 25.6±0.6kg/m²) ingested a study drink on separate study days: (i) 70g whey-protein (P280); (ii) 14g whey-protein, 28g carbohydrate, 12.4g fat (M280); (iii) 70g whey-protein, 28g carbohydrate, 12.4g fat (M504); or (iv) a non-caloric control drink (C).

Results: SBP decreased after all three nutrient drinks compared to the C, with the greatest reduction after the M504 drink (P=0.008). Maximal decreases in SBP (C: -14±2mmHg, P280: -22±2mmHg, M280: -22±4mmHg, M504: -24±3mmHg) occurred about 2 hours after drink ingestion and persisted thereafter (120-180min: P280 and M504 vs. C P<0.05). Maximum DBP decreases and HR increases occurred after M504, with no differences between the effects of the P280 and M280 drinks.

Conclusions: The effects of whey-protein containing drinks to lower BP and increase HR may persist for at least 3 hours after ingestion, and appear to be dependent on their energy content rather than macronutrient composition. Pure whey-protein drinks may represent the best approach to maximize protein intake while minimizing the potential for deleterious BP falls in older people.