Cholesterol and Eggs
Over 30 years of prospective epidemiological surveys of CHD risk have consistently found no independent relationship between dietary cholesterol or egg consumption and CHD risk [1]. In addition, there is strong evidence showing that the effects of cholesterol-rich foods on blood cholesterol are small and clinically insignificant in comparison with the effects of dietary saturated fatty acids (SFA). SFA influence the level of circulating low density lipoprotein (LDL)-cholesterol to a much greater extent than dietary cholesterol in foods such as eggs [2].
This evidence has led to major world and UK health organisations revising their guidance [3], including the British Heart Foundation which has dispensed with its recommendation limiting eggs to 3-4 a week, although people with familial hypercholesterolaemia (1 in 500 in the UK) would still be advised to restrict dietary cholesterol intake. The Food Standards Agency also advises that most people don’t need to limit how many eggs they have, if they are eating a balanced diet. The American Heart Association has also removed specific reference to eggs in their dietary recommendations for heart health.
Changing advice on eggs
The misconceptions around eggs and cholesterol largely stem from incorrect conclusions drawn from early research [1,2,3].
- Research on animals in the early twentieth century, when they were fed foods that were high in cholesterol and saturated fat, led researchers to an oversimplified conclusion that dietary cholesterol was the key component in CHD risk in both animals and humans.
- Later studies proved a definite link between raised LDL-cholesterol and increased risk of coronary heart disease (CHD), but small changes in LDL- cholesterol do not translate into clinically significant changes in CHD risk.
- Early studies on the effects of dietary cholesterol on serum cholesterol levels produced misleading results because the diets contained high levels of saturated fat and/or extremely high amounts of cholesterol (>1000mg per day). Later studies have been able to separate the cholesterol-raising effects of dietary cholesterol from saturated fat, which often exist together in the same foods. Eggs are not high in saturated fat.
- Studies in the 1990s began to look in more depth at the separate effects of dietary cholesterol and saturated fat, which tend to exist together in the same foods. A review of these studies in 2006 [2] concluded that although dietary cholesterol can increase serum cholesterol, both the LDL- and HDL- components are increased. The review noted that the effect was apparent at cholesterol intakes of less than 400mg per day, but was small relative to the effect of saturated fat. In addition, any impact of dietary cholesterol on LDL or CHD risk was potentially offset by a favourable increase in HDL.
References
- McNamara DJ (2000) Dietary cholesterol and atherosclerosis. Biochimica et Biophysica Acta 1529: 310-20.
- Lee A and Griffin B (2006) Dietary cholesterol, eggs and coronary heart disease risk in perspective.Nutrition Bulletin 31: 21–27.
- Gray J and Griffin B (2009) Eggs and dietary cholesterol – dispelling the myth. Nutrition Bulletin 34: 66-70