An Egg a Day? Think Again!
We’ve all been told that eating eggs is one of the most nutritious and convenient dietary decisions we could make. After all, an egg is really a survival capsule for a chick, so it must contain lots of valuable nutrients, right? But are there any drawbacks to that advice?
Turns out that eggs are the top source of dietary cholesterol in the U.S. diet, providing nearly a quarter of all consumed cholesterol, and almost double what people obtain from eating chicken. I would estimate that the figures would be similar in Australia.
An egg generally contains 141 to 234mg of cholesterol, which can increase LDL (Low Density Lipoprotein) cholesterol. This is the bad type. In the U.S., the 2015 - 2020 Dietary Guideline advise eating as little cholesterol as possible, but no limit is given due to inadequate evidence. The prior 2010 guidelines suggested a limit of <300mg a day.  In other words, a single egg will supply all the daily allowable dietary cholesterol to you. Hold the bacon!
Clinical trials show consumption of eggs, for about 2/3 of the population, produces a mild rise in LDL (0.143mmol/L) and HDL (High Density Lipoprotein) (0.055mmol/L) cholesterol. However, about one third of the population are considered high responders, and they experience significant rises in both LDL and HDL cholesterol. HDL function appears to improve with egg consumption. [5,6]
The highest concentrations of saturated fat are found in meats, dairy, eggs, processed foods and oils (including coconut and palm oil). High saturated fat in the diet will promote weight gain and cardiovascular disease, as well as diabetes and cancer.
Indeed, the top food groups to limit or avoid based on lack of nutrients and potential disease promoting components per calorie, listed in descending order are: 
Processed snack foods with added fat, sugar and salt
High fat dairy (especially with added salt and sugar)
Studies suggest an increased risk of diabetes with high egg consumption (≥3 eggs per week), but eggs have not been associated with an increased risk for cardiovascular disease.  [2,3]
However two landmark studies, the Nurses’ Health Study and the Health Professionals Study, at follow-up, demonstrated: [1,9]
People with diabetes who consume more than one egg a day doubled their risk of cardiovascular disease compared to those who ate less than one egg a week.
Eating more than five eggs per week was associated with an increased risk of developing diabetes.
The carnitine and choline found in meat and eggs produced inflammation that lead to diabetes.
Can it get any worse? Well, it turns out that arachidonic acid, found in poultry and eggs, is speculated to lead to neuro-inflammation and thereby affect mood.  It is associated with increased depression rates and the likelihood of suicide.
Based on all this, you would be wise to consider eggs as a special occasion food only. Yes, they’re practical and delicious, but there are substantial health dangers lurking beneath the promotional hype.
Djousse, L., O.A Khawaja, and J.M. Gaziano, Egg consumption and risk of type 2 diabetes: a meta-analysis of prospective studies. Am J Nutr, 2016. 103(2): p. 474-80.
Diez-Espino, J., et al., Egg consumption and cardiovascular disease according to diabetic status: The PREDMED study. Clin Nutr, 2017. 36(4): p. 1015-1021.
Shin, J.Y., et al., Egg consumption relation to risk of cardiovascular disease and diabetes: a systematic review and meta-analysis. Am J Clin Nutr, 2013. 98(1): p. 146-59.
Fuller, N.R., et al., Egg Consumption and Human Cardio-Metabolic Health in People with and without Diabetes. Nutrients, 2015. 7(9): p. 7399-420.
Blesco, C.N. and M.L. Fernandez, Dietary Cholesterol, Serum Lipids, and Heart Disease: Are Eggs Working for or Against You? Nutrients, 2018. 10(4).
Rouhani, M.H., et al., Effects of Egg Consumption Blood Lipids: A Systematic Review and Meta-Analysis of Randomised Clinical Trials. J Am Coll Nutr, 2018. 37(2): p. 99-110.
Greger, M., 2C Nutrition: Foods Overconsumed and Underconsumed, in Lifestyle Medicine Core Competencies. 2015, ACPM: ACPM Education
Beezhold, B.L. and C.S. Johnston, Restiction of meat, fish and poultry in omnivores improves mood: a pilot randomised controlled trial. Nutr J, 2012. 11: p. 9.
Djousse, L., et al., Egg consumption and risk of type 2 diabetes in men and women. Diabetes Care, 2009. 32(2): p. 295-300.