Dietary cholesterol from eggs: the effect on blood cholesterol
Clinical bottom line
Consuming one additional egg a day (about 200 mg cholesterol) will increase the ratio of total to HDL cholesterol concentrations by 0.040 units; increasing the risk of myocardial infarction by an estimated 2%.
RM Weggemans et al. Dietary cholesterol from eggs increases the ratio of total cholesterol to high-density lipoprotein cholesterol in humans: a meta-analysis. American Journal of Clinical Nutrition 2001 73: 885-891.
Dietary cholesterol increases total and LDL cholesterol; established risk factors for coronary heart disease. However, studies have shown that dietary cholesterol also increases HDL cholesterol which may protect against coronary heart disease. It is therefore possible that dietary cholesterol's adverse effect on LDL cholesterol is offset by its favourable effect on HDL cholesterol.
The following meta-analysis reviews the effect of dietary cholesterol, from egg consumption, on the ratio of total to HDL cholesterol. This ratio was chosen because it incorporates the effects of both LDL and HDL cholesterol on coronary heart disease risk.
The literature was searched using MEDLINE (1974 to 1999) and Biological Abstracts (1989 to 1999). Reference lists were then reviewed. Studies were included if they met the following criteria:
- they were published in English;
- their design was either parallel (groups of participants given different diets) or randomised crossover (all participants given different diets in random order);
- the experimental diets only differed in the amount of dietary cholesterol or number of eggs;
- the diets lasted for 14 days or more;
- the HDL concentrations were reported.
Seventeen studies met these criteria. Participants totalled 556 (422 men and 134 women), aged between 18 and 75 years, with an average body mass index (kg/sq m) ranging from 20.8 to 28 and initial cholesterol concentration ranging from 4.06 to 5.92 mmol/L. The change in cholesterol intake ranged from 167 to 897 mg/d.
Assuming one egg contains 200 mg cholesterol, consuming one additional egg a day increased total cholesterol by 0.111 mmol/L, LDL cholesterol by 0.100 mmol/L, HDL cholesterol by 0.016 mmol/L and the ratio of total to HDL cholesterol by 0.041 units. The ratio of HDL to LDL cholesterol decreased by 0.011 units.
In studies with a background diet low in saturated fat, the change in LDL cholesterol was weaker than in those with a background diet high in saturated fat. Each additional 100 mg of dietary cholesterol increased LDL cholesterol by 0.036 mmol/L versus 0.061 mmol/L.
For most people, the effect of dietary cholesterol is minimal and the reduction of total and saturated fat is more important. However, for those with raised blood cholesterol levels (above 5.2 mmol/L), reducing the amount of high-cholesterol foods will help, along with other modifiable cholesterol-lowering behaviours, such as reducing saturated fat intake, increasing fibre consumption, maintaining a healthy weight and exercising. Besides egg yolks, other sources of dietary cholesterol include meat, dairy products, offal and shellfish.