Plasma LDL and HDL characteristics and carotenoid content are positively influenced by egg consumption in an elderly population
Background: Approximately 1/3 of individuals have a high plasma response to dietary cholesterol (hyper-responders). Although increases in both LDL and HDL cholesterol have been observed, limited data exist regarding effects of egg consumption on lipoprotein subclasses and circulating carotenoids. Methods: 29 postmenopausal women (50-68y) and 13 men (60-80y) were assigned to either 3 eggs (EGG, 640 mg cholesterol /d) or an equal volume of cholesterol-free egg substitute (SUB, 0 mg cholesterol/d) for 30d. Following a 3 wk wash out, subjects crossed over to the alternate diet. Individuals with a response to dietary cholesterol > 2.2 mg/dL for each additional 100 mg of dietary cholesterol were classified as hyper-responders while hypo-responders were those with a response < to 2.2 mg/dL. Nuclear Magnetic Resonance (NMR) spectroscopy determined LDL and HDL size & particle concentrations. Dietary records were used to evaluate carotenoid consumption. Results: Hyper-responders had higher concentrations of both LDL cholesterol (LDL-C) and HDL cholesterol (HDL-C) after EGG. In contrast, the concentrations of plasma LDL-C and HDL-C did not differ between the EGG and SUB for the hypo-responders. After EGG, hyper-responders had larger (> 21.2 nm) less atherogenic LDL particles (P < 0.001) and larger HDL particles (> 8.8 nm) (P < 0.01), with no significant difference in the total number of LDL or HDL particles. Regardless of response classification, all individuals had an increase in plasma lutein (from 32.4 +/- 15.2 to 46.4 +/- 23.3 ng/L) and zeaxanthin (from 8.8 +/- 4.8 to 10.7 +/- 5.8 ng/L) during EGG, yet hyper-responders displayed higher concentrations of carotenoids when compared to hypo-responders. Conclusion: These findings suggest that the increases in LDL-C and HDL-C due to increased egg consumption in hyper-responders are due to an increase in the less atherogenic lipoprotein subfractions. Also, increases in plasma carotenoids after EGG may provide a valuable dietary source for this population.