28 January 2021
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Does an egg a day keep the undertaker away?

Dr Ross Walker
23 November 2020

The world waits for the COVID vaccine to be available so we can see the end of our current infective pandemic but , unfortunately, we won’t be seeing the end of the diabesity epidemic, unless the lifestyle habits of millions of people change dramatically over the next decade or so.

In almost all cases, Type 2 diabetes is related to being born with the insulin resistance gene. This gene is present in 30% of Caucasians, 50% of Asians and close to 100% of people with darker skin. But, as with almost all diseases, it’s your genes that loads the gun and your environment that pulls the trigger. This is certainly the case with Type 2 diabetes and, as any community or country becomes more affluent, if they are born with the insulin resistance gene, then the clinical manifestations become more obvious.

With insulin resistance, the key manifestations include pre-diabetes or diabetes; hypertension; a specific cholesterol abnormality known as dyslipidaemia, which includes high triglycerides and low HDL cholesterol, and the increasingly ever-present abdominal obesity. For males, a waist circumference above 95cm and for females, above 80cm is the best indicator of abdominal obesity.

A rather disturbing study was recently released by the University of South Australia analysing a Chinese population of just over 8,500 adults with the average age of 50 as part of the China Health and Nutrition survey. This study analysed the nutrition habits of this population between 1991 to 2009. Part of the study reviewed the prevalence of Type 2 diabetes. As the Chinese community became more affluent, so did their diet. There was a shift from the consumption of healthy grains, fruit and vegetables to a much higher intake of meat, snacks, takeaway food and restaurant dining, along with the consumption of other high energy dense foods and soft drink. Coinciding with this dietary shift was also an increase in the intake of eggs. One egg contains around 50g and in the early 1990s the average daily intake in this group was only 16g. This had risen to 31g by the end of the study. (1)

The study demonstrated that the Chinese adults participating in the survey, who consumed one egg per day or more, had a 60% increased risk for Type 2 diabetes. Although this was a clear finding of the study, it raises more questions than it actually answers. Firstly, was the increased egg intake purely a marker for the consumption of more unhealthy foods that I mentioned in the last paragraph? If increased egg consumption is indeed related to an increased risk for Type 2 diabetes, what is the mechanism?

The gold standard of scientific research is the randomised controlled clinical trial. There has never been a randomised controlled clinical trial of diet in any form because it is impossible to have a placebo group. Even the research on the Mediterranean diet was observational but still, of course, showing significant clinical benefits from following the very healthy eating habits of this particular diet. 

Over the years, there have been a number of conflicting studies around the consumption of eggs. When the entire cholesterol debate started over 50 years ago, there was no doubt that the high cholesterol content of eggs put them in the “eat sparingly” basket. As the knowledge of cholesterol and the associated lipid disorders became more accurate, it was found that 70% of cholesterol was made within the body and had much less to do with dietary intake of cholesterol from foodstuffs, such as eggs and shellfish, which have a high cholesterol content.

A number of studies have been released over the past few decades suggesting that moderate consumption of eggs on a weekly basis is not associated with an increased risk for cardiovascular disease in otherwise healthy populations. A study was published in January 2020 in the British Medical Journal from Harvard University as part of the Nurses Health study and Health Professionals follow-up study. This followed over 216,000 people up to 32 years showing consuming up to one egg per day was not associated with an increased risk for cardiovascular disease, and strangely this study suggested a lower rate of cardiovascular disease in the Asian population who consumed eggs regularly. (2)

The second study, published in the journal Cholesterol in 2018, concluded healthy people who had a moderate intake of eggs on a regular basis, had no increased risk for cardiovascular disease. (3)

It is my opinion that, on balance, the regular consumption of eggs at a moderate level (on average up to 1 per day) does not have an adverse effect on health. In the Chinese population assessed, egg consumption was probably more a marker for a move towards more unhealthy foods, less exercise and the very ubiquitous smoking, present in the Chinese population. There are 360 million smokers living in China where lung cancer is the biggest killer.

Thus, if you enjoy consuming eggs on a regular basis, combine this with healthy living habits such as consuming 2 to 3 pieces of fruit per day, 3 to 5 servings of vegetables per day (one serving is around half a carrot), avoiding other foods that you know have an unhealthy reputation, regular exercise, no smoking and low alcohol consumption, along with healthy sleep habits and most importantly cultivating happiness in your life. I suspect strongly that the eggs will not have an adverse effect on your health.

If, however, you have key features of insulin resistance and especially if you are carrying extra weight, it is vitally important you address all lifestyle issues rather than focusing too much on whether having eggs is going to be a major health issue. Unfortunately, when studies such as these are released, many people focus on the headline rather than analysing many of the factors that are hidden within the fine details of the study.

  1. Wang, Y., Li, M. and Zumin, S. (2020) Higher egg consumption associated with increased risk of diabetes in Chinese adults - China Health and Nutrition Survey' in British Journal of Nutrition​.
  2. Jean-Philippe Drouin-Chartier et al      Egg consumption and risk of cardiovascular disease: three large prospective US cohort studies, systematic review, and updated meta-analysis  BMJ 2020;368:m513 
  3. Heqian Kuang, 1 Fang Yang, 2 Yan Zhang, 1 Tiannan Wang, 1 and  Guoxun Chen 1Cholesterol. 2018; 2018: 6303810.  2018 Aug 23. doi: 10.1155/2018/6303810 The Impact of Egg Nutrient Composition and Its Consumption on Cholesterol Homeostasis

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