Independent Effects of High-cholesterol (High-egg) and High-saturated Fat Diets on LDL-cholesterol

Eggs are high in cholesterol but low in saturated fat. Data from cross-sectional, prospective, and randomized controlled trials (RCTs), suggest that egg intake does not adversely affect blood lipids or increase cardiovascular disease (CVD) risk. In fact, there is some evidence that egg consumption may reduce CVD risk. However, to date there has been no direct comparison of the effects of a high cholesterol (high egg), low saturated fat diet and a low cholesterol, high-saturated fat diet on blood lipids, and no studies have accounted for potential effects of differences in physical activity, which can also influence the blood lipid profile. Evaluations of the effect of egg consumption on blood lipids should include analysis of physical activity as there is emerging evidence that the lutein and zeaxanthin in egg yolk may increase physical activity levels by crossing the blood-brain barrier and altering neuronal function. We will directly compare the effects of a high cholesterol, low saturated fat diet and a low cholesterol, high saturated fat diet on blood lipids, using egg consumption to manipulate dietary cholesterol intake, while also accounting for physical activity levels. The study will investigate effects on a number of novel lipoprotein parameters (particle size and particle concentrations).

Inclusion criteria

• Male or female, aged 18 - 60 years
• Blood LDL-C <3.5 mmol/L (measured at screening using an automated analyser (Cholestech LDX System).
• Non-smoker (or other nicotine products) (minimum 6 months).

Exclusion criteria

• Have diagnosed cardiovascular disease (including uncontrolled high blood pressure) or a chronic disease, including Type-1 or -2 diabetes, kidney or liver disease, gastrointestinal disorders requiring medical nutrition therapy (e.g., Crohn's disease, irritable bowel, coeliac disease) or any other condition that may have an impact on study outcomes.
• Have allergies or strong aversion to eggs or other components of the test foods (diets are not suitable for vegetarians).
• Consume more than 5 eggs per week in the month prior to beginning the trial.
• Participant has a recent history (within 12 months) or strong potential for alcohol abuse. Defined as >14 standard drinks per week.
• Have changed medication or supplementation that might affect study outcomes in the last 3 months.
• Take vitamin, mineral, herbal supplementation, or medications that may have an impact on study outcomes.
• Are already involved in another research project within 30 days of commencement of the present study that in the opinion of the investigators will be unsuitable for this study.
• Are pregnant or breastfeeding.
• Show unwillingness to be randomized to either experimental group.
• Failure to satisfy the investigator regarding suitability to participate for any other reason.
• Are unwilling or unable to provide written informed consent.