The effect of high-fiber oat versus wheat cereal on factors associated with cardiovascular disease risk

Abstract

Foods rich in dietary fiber, particularly those high in soluble fiber, have been recognized by major health organizations as beneficial for cardiovascular disease prevention. According to the Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (2001), major risk factors for cardiovascular disease include elevated blood total and low-density lipoprotein cholesterol (LDL-C) concentrations. Additionally, the American Heart Association (2000) reports that one in four adults in the United States have hypertension, a condition that significantly increases cardiovascular disease mortality. The purpose of this dissertation was to examine the effect of increased fiber-rich oat cereal consumption, as compared to fiber-rich wheat cereal consumption, on blood lipid and lipoprotein concentrations and casual resting and 24-hour arterial blood pressure in middle aged and older men. Thirty-six overweight middle-aged and older men (BMI 25-35kg/m2, aged 50-75 y) with elevated BP (systolic BP 130-160mmHg and/or diastolic BP 85-99mmHg) were randomly assigned to consume an additional 14 g of dietary fiber per day in the form of oat (5.5g β-glucan, n=18) or wheat cereals (no β-glucan, n=18) for 12 weeks. Measurements of plasma lipids and lipoprotein subclasses using proton nuclear magnetic resonance (NMR) spectroscopy were performed before and after the intervention. Casual resting arterial BP was measured at baseline and after four, eight, and 12 weeks of the intervention. 24-hour ambulatory arterial BP was measured at baseline and after 12 weeks of the intervention. There were significant (P<0.05) time-by-treatment interactions for LDL-C (Oat:-2.5%; Wheat:+8.0%), small LDL-C (Oat:-17.3%; Wheat:+60.4%), LDL particle number (Oat:-5.0%; Wheat:+14.2%) and LDL-C/HDL-C ratio (Oat:-6.3%; Wheat:+14.2%). There was a trend for a time-by-treatment interaction for TC (Oat:-2.5%; Wheat:+6.3%, P=0.08), TG (Oat:-6.6%; Wheat:+22.0%, P=0.07) and VLDL-TG (Oat:-7.6%; Wheat:+2.7%, P=0.08). There was no effect of the oat cereal on HDL-C, HDL-C subclasses, or LDL, HDL or VLDL particle diameter. Neither casual systolic or diastolic BP changed as a result of the 12-week intervention in the oat (138/89 vs. 135/88 mmHg) or wheat (142/90 vs. 140/91 mmHg) groups, respectively (all P>0.05). Further, 24-hour, daytime, and nighttime SBP and DBP did not decrease with the intervention. In conclusion, the addition of two large servings of oat as compared to wheat cereal results in lower concentrations of small, dense LDL-C and LDL particle number without producing adverse changes in blood TG or HDL-C concentrations in middle-aged and older overweight men. These beneficial alterations may contribute to the cardioprotective effect of oat fiber. However the consumption of fiber-rich oat cereal (or fiber-rich wheat cereal) has no detectable effect on resting or 24-h ambulatory blood pressure in middle aged and older overweight men with elevated blood pressure. Thus, our findings do not suggest that the cardioprotective effect of oat consumption is due to an arterial blood pressure-lowering effect.