Eggs: The devil is in the detail
By Dr Ross Walker
Just when you thought it was safe to tuck into your favourite dish on the weekend of bacon and eggs, new research was released this week published in the highly acclaimed Journal of the American Association of Medicine suggesting we should rethink this position.
This extensive study pooled data from six US cohorts totalling 29,615 people of whom 45% were males and 31% African Americans. The average age of the people in the study was 52 followed for up to 31 years but on average 17 years. Thus, it was a very large study with a very long follow-up looking at the American population.
The conclusion of the study was each additional intake of dietary cholesterol of 300 mg per day equated to an increase in cardiovascular events of 17% and death from any cause of 18%. In real terms, for each thousand people studied, those who consumed two eggs per day compared with those who didn’t, but otherwise had a similar diet, there were 32 more cardiovascular events and 4 more deaths in the egg consumers. Eggs by themselves were not really the culprit but rather dietary cholesterol, which can come from any animal source.
So, is that the end of the story? Should we never look another egg in the face or tuck into the often-consumed eggs and bacon or one of my favourites, Eggs Benedict?
The clear answer here it is to drill down on the research and find out exactly how the study was done. Once you have understood this, you’ll realise what little credence this information has for your eating habits. Basically, this entire information is based on one dietary questionnaire performed at the start of the study. This questionnaire asked the participants about the food they had consumed either in the previous month or 12 months based on the particular cohort investigated. Could you remember accurately what you consumed during these periods?
There were no further questionnaires administered and basically the health and disease events were followed for the next period up to 31 years but on average 17 years. Clearly, any intelligent human being would question the validity of such a study. Many people change their dietary and life habits over such a long period of time. Many people become ill and often radically change their diets as well.
Another recent study looked at young and ageing mice and compared their vascular health pre- and post-antibiotics. They found that a course of antibiotics did nothing to the vascular health of the younger mice but profoundly improved the vascular health of the older mice. The hypothesis here is that as mice age, the gut bacteria changes to become more pathogenic. Young healthy people have young healthy gut bacteria. With years of exposure to western diets which may include eggs or not, our gut bacteria change from the young healthy pattern to older, more pathologic bacteria and liberate toxic chemicals into the bloodstream. There has been a significant amount of work around the chemical TMAO, which has been found to have a direct toxic effect on blood vessels, making them much stiffer and more prone to atherosclerosis, the basic underlying cause for heart disease. It appears that predisposed individuals who do have a diet high in animal products may liberate more TMAO into their bloodstreams from the interaction of these animal products and defective gut bacteria.
But, over the past two years there have been two components of a trial known as the PURE study both of which have put this cholesterol and saturated fat argument to bed. The PURE study was conducted in 50 different countries, not just America, where we all know that dietary habits for many people living in America are very poor. It may be that it is not those couple of extra eggs per day consumed with a typically poor American diet that needs radical rethinking, but the overall diet itself.
The first component of the PURE study, released in 2017, looked at 135,000 people in 50 different countries followed for nine years and showed that those with the highest carbohydrate intake had a 28% increased death risk, where as those with the highest fat intake had a 23% reduction in death and those with the highest saturated fat intake i.e. animal products, had a 14% reduction in death.
The second component of the PURE study, released in 2018 followed 220,000 people in 50 different countries again for nine years and shows that those people who had three servings of high-fat dairy and 100 g of red meat on a daily basis had a 25% reduction in death and cardiovascular disease.
It is my opinion, from a more global analysis of the literature, that if you are enjoying eggs on a regular basis but are combining this with other healthy dietary patterns, clearly not the norm in America, that the evidence for harm is non-existent. We should be more focused on our overall lifestyle and dietary patterns and maintaining healthy gut bacteria through the consumption of at least 2 to 3 pieces of fruit per day and 3 to 5 servings of vegetables per day, rather than demonising one particular food i.e. eggs. The reality is that eggs contain high-quality protein, many essential vitamins & minerals, along with lutein-which is very good for the eyes; choline - essential for the memory and of course, cholesterol which is the basic, natural chemical essential for many normal and healthy compounds produced on a daily basis.
Medical science is essential to continue to improve the health of society but it doesn’t mean that the research is always correct and shouldn’t be questioned. I certainly question this study that makes rather emphatic conclusions based on one dietary questionnaire performed at the start of the study and not any further analysis of the person’s lifestyle for the next (at least) 17 years. You make up your own mind, but, for mine, I will continue to practice healthy lifestyle principles and enjoy eggs when I feel like eating them.