Title

The individual response to a diet high in cholesterol provided by eggs: Does response affect coronary heart disease risk?

Date of Completion

January 2004

Keywords

Health Sciences, Nutrition|Health Sciences, Public Health

Degree

Ph.D.

Abstract

Extensive research has not established a link between egg intake and CHD. The objective of this dissertation was to address four research questions: (1) What changes occur in the plasma compartment following egg intake? (2) How does egg intake affect the intravascular remodeling of lipoproteins? (3) Do hyper-responders experience a similar plasma response to other egg components? (4) Are there genetic determinants of the plasma response to dietary cholesterol? Utilizing a randomized, crossover design, 40 males and 51 pre-menopausal women, were assigned to an egg (640 mg/d dietary cholesterol) or placebo (0 mg/d dietary cholesterol) diet for two 30 d periods, which were separated by a 3 wk washout. Subjects were classified as hypo- (no fluctuation or a slight increase in TC of <14 mg/dL) or hyper-responders (increase in TC of >16.0 mg/dL) following additional dietary cholesterol consumption. Data analysis was divided into five studies. The first two studies found that hyper-responders, experienced significant increases in TC as a result of elevations in both LDL-C and HDL-C. Despite this increase, female hyper-responders did not experience changes in their LDL/HDL ratio. Male hyper-responders had an increase; however, the average ratio was within the optimal range. In the third study, the less atherogenic LDL-1 sub-class was significantly greater in all hyper-responders. Because eggs are rich in lutein and zeaxanthin, we found that hyper-responsive men and women had significantly higher levels of these carotenoids than hypo-responders. Because these carotenoids are powerful antioxidants associated with LDL in circulation, they may function to protect against CHD. The final study examined polymorphisms of the APOE, ABCG5, APOA4 and APOC3 genes to determine if the variation in plasma response could be explained by genotype. Fluctuations in HDL-C were better explained by gender and baseline HDL-C concentrations than genotype. However, ABCG5 and APOA4 347 genotypes were able to predict the variation in TC and LDL-C following EGG intake by 5.2% and 3% respectively. Furthermore, carriers of the ABCG5 C/C allele had significantly higher TC and LDL-C levels following egg intake. These findings indicate that egg consumption does not increase CHID risk in healthy men and women, regardless of response classification. ^