A number of changes to blood lipids have been identified that alter the risk of developing cardiovascular disease. These including increases in plasma low density lipoprotein (LDL) cholesterol, increases in triglycerides, increases in lipoprotein(a), decreases in high density lipoprotein (HDL) cholesterol, as well as the phenotypic expression of the pattern B subfraction of small dense LDL cholesterol. A number of dietary factors are known to modify blood lipids including fish oils, fibre, phytonutrients such as sterols and garlic. High concentrations of dietary cholesterol are recognised by mainstream medical authorities as being linked to detrimental changes in blood lipid levels, however the role for dietary cholesterol in the development of cardiovascular disease is controversial. While in certain individuals with a particular genetic make up, cholesterol intakes may have an influence on blood lipid levels, amongst the majority of healthy individuals this appears not to be the case.
For example, research1 has investigated the effects of dietary cholesterol from whole eggs on the changes to blood lipids in Mexican children aged between 8 and 12. The children (25 boys and 29 girls) were assigned to receive either 2 whole eggs per day which equated to an additional 518 mg of cholesterol in their diet, or a similar amount of egg whites which contained no cholesterol. After 30 days of treatment the children followed a normal diet for two weeks before being assigned to the opposite group. Subjects that had increases in total blood cholesterol of ≥0.06 mmol/L (hyper-responders) after whole egg treatment showed elevations in both LDL cholesterol and HDL cholesterol but no change in the LDL to HDL ratio. Those subjects who had a total blood cholesterol rise of ≤0.05 mmol/L (hypo-responders) also had no changes to their LDL:HDL ratio. As the LDL to HDL ratio is a greater risk factor than the absolute amount of either lipoprotein, these results suggest that there was no alteration is cardiovascular risk.
A growing body of research is starting to question the theory that dietary cholesterol is responsible for deleterious changes in blood lipids. Even in those subjects who had the largest increase in total cholesterol blood levels (≥0.06 mmol/L) in response to the whole egg treatment, the ratio of LDL:HDL remained constant suggesting that cardiovascular disease risk had not changed. Interestingly, in all subjects the whole egg consumption caused increases in LDL diameter and a decrease in the small LDL subfractions that is a known risk factors for cardiovascular disease. In the study 15 % of the subjects were identified as having the high risk LDL phenotype B, but on consumption of eggs changed to the low risk pattern A phenotype. These results taken together suggest that cholesterol from eggs in not detrimental to blood lipids, but may actually be beneficial in certain individuals. This may relate to the high concentrations of lecithin is eggs, a substance that is known to beneficially affect lipoprotein metabolism.
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