In Defense of the Egg

Doc Gumshoe, over easy, with a side of cholesterol

Doc Gumshoe is not in the habit of contradicting the conclusions, backed by research, that are stated in papers published by the Journal of the American Medical Association, commonly referred to as JAMA.    JAMA is, after all, one of a handful of the most prestigious medical journals on the planet, along with the New England Journal of Medicine (NEJM), Lancet, and the British Medical Journal (BMJ).

The JAMA paper rocketed around the media like hot news about one of those current celebrities whose names I barely recognize, but everybody else seems obsessively to follow.   There are 718,000 Google links to the subject line “JAMA eggs are bad.”   

What the JAMA paper concluded was that “Among US adults, higher consumption of dietary cholesterol or eggs was significantly associated with higher risk of incident CVD and all-cause mortality in a dose-response manner.”   Specifically regarding eggs, the paper’s conclusion was that each additional half an egg consumed per day was associated with a 6% higher risk of cardiovascular disease and an 8% higher risk of all-cause death.   (Zhong VW et al. JAMA 2019:321(11):1081-1095).   (More about the specifics of that study later.) 

Anti-egg bias has a long and distinguished history.   It is not, for example, in any way comparable to the many totally irrational biases that plague honest health-care professionals and cause harm to the commonwealth.   I will quote from an excellent book, Medicine’s Ten Greatest Discoveries, by Meyer Friedman, MD, and Gerald Friedland, MD (Yale University Press, 1998):

“Ask any zoologist or epidemiologist what animal has killed and is still killing more humans than any other animal.   The answer would surely be the cobra.   Despite the availability of anti-venom therapy, this wretched snake still kills five thousand to ten thousand Indians alone each year.   A herpetologist would incriminate not the relatively long (10 – 15 feet) king cobra, but the short (5 feet) Indian snake (naja naje).   This reptile ranks as the most deadly because of its habit of slinking into houses at dusk in search of rats and mice, then being surprised ay an unsuspecting human victim, into who it buries its lethal fangs.

The specialists would be in error.   The most murderous animal for millennia has been and still is the seemingly gentle hen.   She does not kill us by fang or claw, but by presenting us with the product of her ovary.   The yolk of her egg contains ten times as much cholesterol as is found in a similar quantity of beef, pork, fish, or even chicken flesh.   No other body organ or tissue (except the brain) is so loaded with this lethal substance.”

In order to understand why pinning the cause of cardiovascular disease on eggs because of their high cholesterol content is still controversial, we have to take a look at the history of the relevant medical and physiological discoveries. 

More about cholesterol

The role of cholesterol in cardiovascular disease (CVD) began to be understood in the first decade of the 20th century.   There had been several theories about the cause of what was then called “hardening of the arteries” or “arteriosclerosis,” including that it was simply the result of aging, or that it was due to disturbed metabolism of the artery itself, or that the process evolved from clots adhering to the arteries which then absorbed the clots, becoming arteriosclerotic plaques.   The first real breakthrough came in 1910 when a scientist named A. Windhaus published a paper reporting that lesions in the inner lining of sclerotic arteries contained six times as much free cholesterol as normal arteries, and about 20 times more esterified cholesterol.         

Around that time, a Russian scientist named Nikolai Anichkov directed an experiment in which rabbits were fed three different diets.   One group got a supplement made from muscle fluid, a second group was on a diet of egg whites, and the third group was fed egg yolks.   Only the third group of rabbits developed the characteristic deposits in the lining of the arteries.   The deposits were identified as cholesterol.   Further research seemed to establish that cholesterol alone was the cause of those arterial changes, and Anichkov published an influential paper in 1913 citing the evidence that demonstrated that the arterial deposits were directly caused by cholesterol in the diet.   That finding has been called one of the ten greatest discoveries in the history of medicine.   

Taking the cue from those findings, the term “atherosclerosis” began to be employed to describe arteries affected by cholesterol deposits, gradually replacing the earlier term, “arteriosclerosis.”    The “athero” part of the term indicates that the substance that is deposited in the arterial wall is a thick, gruel-like substance, whereas the earlier term just referred to arterial hardening.                                          

From those entirely legitimate findings came the conclusion that, since the deposits in the arteries were cholesterol, the way to prevent the development of atherosclerosis (and the harmful consequences following from atherosclerosis) was to eliminate cholesterol from the diet to the greatest extent possible, and since egg yolks are exceedingly rich in cholesterol, the prime dietary culprit that should be extirpated was the egg.   The logic seemed to be irrefutable.

One would think that for the rest of the 20th century, the case was evident:  consuming eggs and other cholesterol-laden foodstuffs (e.g., red meat) led directly to gunked-up arteries and heart disease, and that the way to avoid heart disease was to steer clear of those lethal things.   But perhaps it was because Anichkov’s findings took a long time to be kno