Eggs are considered detrimental to the health by many because of their high content of cholesterol and saturated fat. However, the role of the egg in human nutrition has been distorted considerably. This is particularly true when considering the types of lipids in chicken eggs. Eggs are a rich source of cholesterol for example, but the role of cholesterol in cardiovascular disease has been misunderstood. While an association exists between plasma levels of some cholesterol carrying lipoproteins and cardiovascular disease, the cause and effect has never been conclusively evidenced. Rather like a fire engine being present at the scene of an accident, no sane person would conclude that fire engines are the cause of accidents. As with cholesterol, its presence in the plasma and accumulation in the atherosclerotic plaque do in no way implicate it as the causative in cardiovascular disease. Further, dietary intakes of cholesterol are not able to alter plasma levels of cholesterol and so the point is quite moot.
The saturated fat content of eggs has also been misunderstood. Eggs from battery chickens do contain high amounts of saturated fat, and this relates to the sterile grain diets these birds are fed to allow them to be farmed intensively. However, free range chicken eat their natural diet which contains many varied foods including insects and parts of plants. This gives the nutritional content of the egg a quite different appearance. In particular, the saturated fat in the free range egg is replace to some extent by the omega-3 fatty acid alpha linolenic acid. As most Westerners consume too little omega-3 fat, eating free range eggs is a good way to rebalance this deficiency. Further alpha linolenic acid, like other dietary omega-3 fatty acids, may be cardioprotective. That the role of saturated fat in cardiovascular disease has not been conclusively evidenced adds weight to the contention that eggs from healthy free range chickens are not detrimental to the health of the cardiovascular system.
Chicken eggs are also a very good source of protein, and this gives them some useful nutritional properties. Protein is increasingly being seen as a weight loss food. This may relate to the ability of protein to slow the passage of starch through the gut, particularly the stomach, which in turn confers beneficial glycaemic effects. These glycaemic effects reduce the release of insulin and this may produce benefits to satiety, wakefulness and energy production. Consuming eggs for breakfast with starchy foods such as bread or oats therefore produces desirable effects on blood sugar that may reduce the risk of overeating between meals. Regulating blood sugar by controlling insulin levels may improve mental focus because lower insulin levels reduce the transport of blood L-tryptophan into the brain, which can then subsequently be converted to serotonin and melatonin. As melatonin induces sleepiness, higher protein lower starch breakfasts may effectively increase productivity in the early morning through increased wakefulness.