A new study of more than 300 people of Mediterranean origin has provided further good news for egg lovers but also exposed the complexities involved when analysing such studies.
Eggs have been subject to fluctuating fortunes over the decades, at times being denounced for their high levels of saturated fatty acids and significant amounts of cholesterol, which are generally seen as enemies of heart health.
However, as we reported in YourLifeChoices in June, a follow-up study done by Peking University identified how the ‘good cholesterol’ in eggs helps eliminate the ‘bad cholesterol’, providing strong evidence supporting regular consumption.
Now, the latest research published by scientists based in Greece and Australia has added further weight to that finding. The analysis of men and women living in Athens looked at the 10-year cardiovascular effects of self-reported egg consumption.
The short summary of its findings is that eating one to three eggs a week is associated with a 60 per cent lower risk of developing cardiovascular disease.
Now the attentive among you will note that this weekly figure varies from the one we reported last year, which suggested that eating around seven eggs a week would likely help your cardiovascular health.
Cynics might be tempted to invoke the immortal words of Samuel Langhorne Clemens – aka Mark Twain – at this point: “There are three kinds of lies: lies, damned lies, and statistics.”
And to a degree, Twain’s words do have some relevance here. A closer reading of the latest study identifies several seemingly contradictory statistics.
For example, the study abstract includes this statement: “Unadjusted analysis revealed that 1–3 eggs/week and 4–7 eggs/week were associated with a 60 per cent and 75 per cent, respectively, lower risk of developing CVD compared with the reference group (<1 egg/week).”
On the face of it, that is validation of the Chinese study’s ‘egg a day’ advocacy. But the statement’s very first word – ‘unadjusted’ – provides an immediate caveat. Studies such as this will more often than not require adjusting for sociodemographic, lifestyle and clinical factors.
This may seem like an example of the statistical trickery Twain implied, but it is based on solid mathematics and science. When I was at university in the 1980s, many of my friends who were studying psychology would complain about having to do a statistics unit. However, it was vital they understood concepts such as standard deviation so they could both create meaningful studies and interpret them correctly.
By the time you reach the ‘Conclusions’ segment of the newest study, yet another recommended range of egg consumption pops up: “A consumption level of 2–4 eggs/week is the current recommendation of most health bodies and international guidelines. The findings presented here seem to be overall in line with this recommendation.”
As a good study should, this one provides details of its limitations, but there are those who would argue it might have been better designed. One such person is Dr Angela Zivkovic, associate professor and leader of the Zivkovic Lab at the University of California.
Dr Zivkovic, who was not involved in the current study, has reservations about any studies that involve self-reporting, suggesting that leaves studies open to participants providing misinformation.
“Ask yourself how well you remember what you ate for breakfast two days ago, much less six months ago, unless you happen to be someone who eats the exact same thing for breakfast each day,” she said.
Self-reporting participants may also feel inclined to report what they think they are supposed to have eaten, says Dr Zivkovic: “You may be reporting more on the psychology and memory than the actual food intake.”
Complicating matters still further, she says, are all the other foods included your diet, as well as what foods you do not consume.
“If I designed the study such that people were fed three eggs for dinner in the intervention group and the control group ate pork sausages instead, you would probably find the group eating eggs had reduced risk,” Dr Zivkovic said. “But if the control group ate a salad loaded with carotenoid-rich vegetables with egg white as the protein source, you might find the salad group as the one with the reduced risk.”
So can we cut through all those varying factors and come up with a definitive number of eggs we should consume each week? Basically no, but we can use various peer-reviewed studies to identify a range that is likely, not guaranteed, to benefit you.
Even then, no two individuals are the same.
Cardiology dietitian and preventive cardiology nutritionist Michelle Routhenstein perhaps sums it up best: “High cholesterol and choline content of eggs may be a problem for certain individuals who are at risk for heart disease. So, while eggs may be able to be included in a heart-healthy diet, the amount should be relatively limited. The whole diet should be evaluated for optimal risk reduction.”
That might make things as clear as a poached egg white to some but, unless your health specialist recommends otherwise, there’s a pretty good chance that eating a number of eggs per week will probably do you good.
Just don’t ask me exactly what that number is!
How many eggs do you eat each week? Do you regularly consult your GP about the effects of your diet on your heart health? Why not share your thoughts in the comments section below?
Also read: Understanding cardiovascular disease