Comment by Kevin McConway

A fundamental issue with any study like this is that it can’t determine what causes what, only give hints and suggestions. That’s because, for instance, there will be many other differences between people that eat many eggs and people that eat few other than their egg consumption. These other differences might be what’s causing higher death rates in people who eat a lot of eggs, rather than anything to do with the eggs themselves. [...] But they, correctly, point out that their own study is still not immune from this problem (known as residual confounding), and that therefore it’s impossible to conclude from this new study that eating eggs, or consuming more cholesterol in the diet, is the cause of the differences in cardiovascular disease rates and overall death rates that they observed.