Relation of Meal Frequency (3 vs. 6 meals/day) and Macronutrient Composition (higher vs. lower protein) on Endothelial Function

Authors:
Max Ruby

Advisor:
Dr. Paul Arciero and Dr. Denise Smith

Abstract:

Purpose:
The purpose of this study is to examine the effects of macronutrient composition and meal frequency on blood flow and endothelial function and mediated by weight loss, inflammatory markers and insulin sensitivity during a two-month dietary intervention study.

Methods:
Twenty-eight subjects were assigned to one of three diet groups: a high-protein six meal a day diet, HP-6 meal, (6 meals/day; 40% CHO, 40% PRO, 20% FAT), a traditional 3 meal a day diet according to the American Heart Association, AHA, (3 meals/day; 60% CHO, 15% PRO, 25% FAT), and a 3 meal a day high protein diet, HP-3 meal, (3 meals/day; 40% CHO, 40% PRO, 20% FAT). On day 28, the diet was adjusted to create a 25% caloric deficit, while keeping macronutrient composition and meal frequency constant. Resting blood flow and endothelial function were tested using strain gauge plethsmography. Resting blood flow and endothelial function were tested on days 1, 28, and 56 at baseline, 30 and 90 minutes postprandial. Il-6, Il-8 and TNF-a were determined from blood samples were collected at baseline on days 1, 28, 56.

Results:
No significant differences were detected in resting blood flow. Endothelial function, as expressed by reactive hyperemia blood flow, improved significant in the AHA group from day 1 to 56. There were no other significant findings between baseline measures or postprandial endothelial function in any group. The compilation (n=14) of subjects for whom blood data is available experienced significant decreases in IL-6 and TNF-a. There was no significant change in Il-8.

Conclusion:
The AHA group had significantly improved endothelial function, likely due to improved insulin sensitivity. Postprandial endothelial dysfunction was not present. The decrease in Il-6 and TNF-a are encouraging, but do not appear to have affected endothelial function.