The diet-heart hypothesis of cardiovascular disease suggests that dietary cholesterol and saturated fat are the cause of elevated plasma cholesterol and triglycerides which subsequently cause cardiovascular disease. Foods high in cholesterol and saturated fatty acids are therefore implicated as a direct cause of cardiovascular disease by this theory, and the recommendation is to limit these foods from the diet in order to maintain cardiovascular health. However, feeding studies have failed to demonstrate consistent elevations in plasma cholesterol or fasting triglycerides with increases in dietary cholesterol or saturated fat. In addition, while elevated levels of low density lipoprotein (LDL) cholesterol are associated with cardiovascular disease, the cause and effect has not been proven. Recent evidence regarding nuances in sub-types of lipoproteins suggest that the diet-heart hypothesis was based on oversimplified analysis of data. Further, the theory is demonstrably false because in certain sub-groups high plasma cholesterol reduces mortality.
However, research is slow to permeate through to mainstream healthcare, where the diet-heart hypothesis of cardiovascular disease is still considered relevant. As a result many people avoid perfectly healthy foods because they are considered contain high levels of saturated fat and cholesterol. Eggs are one such food that can provide vital nutrients and protein to a diet, and to which evidence does not associate consumption with increased risk of cardiovascular disease. For example, Researchers1 have reviewed the literature regarding the effects of eggs on cardiovascular disease. Results showed that dietary cholesterol was reported to be associated with a modest increase in the risk of coronary events, but that most studies failed to take account of confounding variables. When other dietary factors were considered, the increase in coronary event was only a 6 % increase with a 200mg / 1000 kcal increase in cholesterol.
A typical 2000 kcal diet would therefore require an increase of 400 mg of cholesterol, or two eggs per day, to increase the risk of a coronary event by 6 % over a lifetime. Several studies have found increased cardiovascular disease risk with increased egg consumption, but all of these studies have failed to allow for confounding variables. For example, eggs contribute on average only 30 % of dietary cholesterol and therefore the major contributors to dietary cholesterol were not considered by these studies. This would create background noise upon which it would very difficult to attribute any effects on plasma cholesterol to eggs. In addition, high cholesterol diets also tend to be low in protective foods such as fibre. Controlling for such confounding variables shows that consumption of one or more eggs per day has no significant effect on cardiovascular risk.