The egg is a cheap food, easy to obtain, which provides a large quantity and variety of proteins and fats (saturated, monounsaturated and poinnsaturated), cholesterol and many vitamins. With regard to cardiovascular risk, many analyses have been carried out depending on how it affects cholesterol levels, but this type of assessment is not very useful. Firstly, because it has been repeatedly demonstrated that the intake of eggs does not usually affect colestrol in blood in most people (not to mention the discrepancies that there are in some circles regarding the levels of cholesterol most recommended by studies such as this). Secondly, because it is more practical to skip the intermediate step of cholesterol and analyze directly what the studies say about its relationship with cardiovascular disease.
It is relatively simple to analyze the short-term effect of eating eggs frequently. Intervention studies show that they are mostly positive. If we refer to the long term, decades ago several researches were carried out that related their intake with an increase in cardiovascular risk. An article like this has even been published recently: Dietary cholesterol and egg yolks: Not for patients at risk of vascular disease in 2010 (it is an opinion-review, not epidemiological) alerting of the risks of eating eggs, with the consequent subsequent discrepant responses (so that they later say that there is scientific consensus).
The problem with old epidemiological studies is that they did not isolate the effect and possible influence of other foods. That is, the increased risk could be caused by the egg, bacon, coffee or butter toast that usually accompanies eggs. Or by any other factor. This is highlighted by the probably best reviews that have been made on the subject and which I strongly recommend reading: A Review of Scientific Research and Recommendations Regarding Eggs (2004) and Egg Consumption and Coronary Heart Disease: An Epidemiologic Overview (2000).
As the methodology of the studies was refined, especially by separating in more detail the influence of different foods, the risk disappeared. It occurred most dramatically in the famous massive 1999 study "A Prospective Study of Egg Consumption and Risk of Cardiovascular Disease in Men and Women," which followed nearly 120,000 people for 14 years. No increased cardiovascular risk was found among people who ate more than one egg a day (although it was found among people with diabetes).
Since then and over the last ten years most studies have reached similar conclusions.
- For example, in "Regular egg consumption does not increase the risk of stroke and cardiovascular diseases (2006)" more than 10,000 people were followed for 4 years and no increased risk was seen among those who ate more than 6 eggs a week.
- Or in "Egg consumption and risk of type 2 diabetes in older adults (2010)", with 4000 people followed for 18 years, the risk of diabetes was also not seen to increase.
- Even in some, such as Egg consumption and CHD and stroke mortality: a prospective study of US adults (2010), analysing some 30,000 people over 6 years, the inverse relationship was found: Eating more eggs reduced the risk.
Admittedly, there have also been some who have found some relationship lately. But although they have obtained statistically significant results, these have been small, which reduces their relevance and does not rule out the influence of other variables.
- For example, in "Egg Consumption and Risk of Heart Failure in the Physicians' Health Study (2008)" it was observed that the risk was increased by 28% if more than one egg per day was eaten and 68% if more than 2 eggs per day were eaten.
- Or in "Egg Consumption and Cardiovascular Disease and Mortality The Physicians Health Study (2008)," it increased 23% by eating more than one a day.
A number of positive results that have been obtained among people with diabetes remain to be clarified. Let us hope that future research will shed light on this.
In conclusion, my view is that there is no compelling evidence that eating eggs is a health risk, and they are an exceptional and affordable nutritional option. As I have said on other occasions, I think it is much more important to eliminate factors with a demonstrated increased risk: stress, sedentary lifestyle, smoking, obesity, refined carbohydrates, alcohol and so on. If you are very prudent, you can limit yourself to one egg a day, as all the most recent and rigorous studies do not find any risk up to this amount. It will be enough for you to watch your usual blood indicators and results to monitor how your body responds and if, as expected, you do not see anything out of the ordinary, you will even be able to increase this amount considerably without any problems.
You also don't need to emulate Margaret Tatcher, with her 28 eggs a week.