Nutrition Science Is Broken. This New Egg Study Shows Why.

At turns lauded and vilified, the humble egg is an example of everything wrong with nutrition studies.

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  • Are eggs good or bad? That depends on what study you’re reading.

    Visual: kajakiki via Getty Images


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It’s been a tortuous path for the humble egg. For much of our history, it was a staple of the American breakfast — as in, bacon and eggs. Then, starting in the late 1970s and early 1980s, it began to be disparaged as a dangerous source of artery-clogging cholesterol, a probable culprit behind Americans’ exceptionally high rates of heart attack and stroke. Then, in the past few years, the chicken egg was redeemed and once again touted as an excellent source of protein, unique antioxidants like lutein and zeaxanthin, and many vitamins and minerals, including riboflavin and selenium, all in a fairly low-calorie package.

This March, a study published in JAMA put the egg back on the hot seat. It found that the amount of cholesterol in a bit less than two large eggs a day was associated with an increase in a person’s risk of cardiovascular disease and death by 17 percent and 18 percent, respectively. The risks grow with every additional half egg. It was a really large study, too — with nearly 30,000 participants — which suggests it should be fairly reliable.

So which is it? Is the egg good or bad? And, while we are on the subject, when so much of what we are told about diet, health, and weight loss is inconsistent and contradictory, can we believe any of it?

Quite frankly, probably not. Nutrition research tends to be unreliable because nearly all of it is based on observational studies, which are imprecise, have no controls, and don’t follow an experimental method. As nutrition-research critics Edward Archer and Carl Lavie have put it, “’Nutrition’ is now a degenerating research paradigm in which scientifically illiterate methods, meaningless data, and consensus-driven censorship dominate the empirical landscape.”

Other nutrition research critics, such as John Ioannidis of Stanford University, have been similarly scathing in their commentary. They point out that observational nutrition studies are essentially just surveys: Researchers ask a group of study participants — a cohort — what they eat and how often, then they track the cohort over time to see what, if any, health conditions the study participants develop.

The trouble with the approach is that no one really remembers what they ate. You might remember today’s breakfast in some detail. But, breakfast three days ago, in precise amounts? Even the unadventurous creature of habit would probably get it wrong. That tends to make these surveys inaccurate, especially when researchers try to drill down to specific foods.

Then, that initial inaccuracy is compounded when scientists use those guesses about eating habits to calculate the precise amounts of specific proteins and nutrients that a person consumed. The errors add up, and they can lead to seriously dubious conclusions.

A good example is the 2005 study that suggested that eating a cup of endive once a week might cut a woman’s risk of ovarian cancer by 76 percent. There was even a possible mechanism to explain the effect: Endive is high in kaempferol, a flavonoid that has shown anticarcinogenic properties in laboratory experiments. It was a big study, based on a cohort of more than 62,000 women. This study was published in the prestigious journal Cancer, and many in the media were convinced. Dr. Mehmet Oz even touted it on his television show.

But, as Maki Inoue-Choi, of the University of Minnesota, and her colleagues pointed out, the survey had asked about many other kaempferol-rich foods — including some that had higher levels of kaempferol than endive does — and not one of those other foods had the same apparent effect on ovarian cancer.

The new study linking eggs and cardiovascular disease deserves similar scrutiny. Statistically speaking, 30,000 participants makes for a very powerful study. And in fairness, the study’s defenders say that it did a good job accounting for factors that might have influenced the findings, such as overall fat consumption, smoking, and lifestyle.

But on the other hand, the study tracked participants’ health outcomes over periods ranging from 13 to more than 30 years, and participants were queried about their diet only once, at the beginning of the study. Can we assume that the participants gave a reliable depiction of their diet at the outset, and then that they maintained that same diet for the years — in many cases, decades — that followed? Probably not. Who eats the same way for 10 years?

In light of these flaws, Dr. Anthony Pearson, a cardiologist at St. Luke’s Hospital in suburban St. Louis, had this advice: “Rather than drastically cutting egg consumption,” he wrote in a blog for MedPage Today, “I propose that there be a drastic cut in the production of weak observational nutrition studies and a moratorium on inflammatory media coverage of meaningless nutritional studies.”

Instead of observational studies, most nutrition scientists would rather see experimental studies like those performed by the late Dr. Jules Hirsch. A pioneer in the study of obesity, Hirsch got his start in the 1950s, long before weight control became the problem that it is today. He took a relatively unglamorous, ignored area of medical health and made it extremely interesting. To this day, his controlled experiments on human nutrition are considered a gold-standard in nutrition science. He discovered that when a person diets, their heart rate slows, they feel cold, and their immune system is undermined.

But here’s the rub: Hirsch worked at Rockefeller University — a serene little campus tucked away on the Upper East Side of Manhattan — where researchers are free to follow their muse, free of teaching duties. Rockefeller University also has a hospital. Between that and the endowment support, Hirsch was able to do research that would have been impractical to do virtually anywhere else.

Hirsch started with basic science, looking at fat cells and how they functioned. Then he moved on to patients. He would admit them to the university hospital and keep them there, assigning them to a metabolic ward where he could control nearly everything they ate. That was critical, because it is really hard to be on a restricted diet, and there are temptations.

In perhaps his most famous study, Hirsch admitted 18 obese men and women to the hospital together with 23 people who had never been obese. He fed them all mostly a liquid diet to control their calories precisely. First, he had them maintain their initial weight and took measurements. Then he had them gain 10 percent of their initial weight and took measurements. Finally, he limited their portions, causing them to go at least 10 percent below their initial weight, and repeated the measurements a third time.

The experiment revealed the now-well-known fact that when an individual loses weight, their metabolism slows. That’s what makes it so hard to lose weight — and to keep the weight off afterward.

Unfortunately, it is impractical — and probably impossible — for most researchers to carry out those types of studies on a large scale. Crunching the data from a big observational study is a much easier way to get a publication and some media attention. So we get what we get.

In the meantime, what do the rest of us do with our diets?

Most experts recommend avoiding processed foods as much as possible and sticking with a Mediterranean-like diet because it makes intuitive sense. It is not too restrictive. It is heavy in fruits and vegetables. It has the right kinds of fats and some grains. It includes fish and generally lean proteins.

These experts contend that you should also be wary about foods that are said to have newly revealed healthy, or unhealthy, properties. In other words, don’t buy the notion of superfoods. The evidence is just not there.

In an email, Michael Blaha, a cardiologist at Johns Hopkins University who has written about methodological issues with nutritional science, told me he finds “particularly distasteful studies of one particular food (e.g., broccoli) or one particular macronutrient,” because “it is impossible to disentangle the effect of one particular food or one macronutrient from the accompanying foods and macronutrients that characterize a typical dietary pattern.”

To put it another way: Eat what you like but keep it balanced. And, perhaps, long live the omelet!


Timothy F. Kirn is a freelance writer based in Sacramento, California. He was formerly an assistant editor at the Journal of the American Medical Association, a reporter for the Rochester Times-Union in New York, and an MIT Knight Science Journalism fellow.

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322 comments / Join the Discussion

    I am co-principal investigator in a human study approved by the University of California San Francisco Medical School, and am continually amazed at how the pseudo-data from memory based observational studies can con1tinue to be accepted as anything but delusional.

    This Mayo Clinic paper — https://www.americanscientist.org/article/reasonable-versus-unreasonable-doubt — totally demolishes observational nutrition studies in such a devastating manner that one wonders why anyone is still stupid enough to do one.

    In 1910,John D.Rockefeller had monopolized the US oil industry.Not content,he sought to do same w/chemical industry (see Flexner report) and the AMA wed the pharmaceutical industry.Give a rabbit sugar 2 raise it’s cholesterol.Cholesterol(endogenous) allows nerve transmission, Statin drugs make $.Etymo0logy of nurse= nourish…

    Did the study ask what the subjects of the study ate WITH their eggs? A good number of people who eat eggs do so with a side of bacon!

    I am skeptical of studies that include such a small percentage of the population, 30,000 out of millions.. How can a natural diet be unhealthy.? Experts keep reversing what they have told us in the past.. My husbands family has a history of heart disease.. In 1978 he had tests done that said he was not in need of surgical intervention.. His cholesterol was high but his arteries were clear.. I followed their guidelines scrupulously.. He gave up his favorite foods hoping to live long enough to see our children grown.. When he died, less than two years later, the coroner said his arteries were closed down to pin-head size.. He gave up his favorite foods and still died.. Since then I feed myself and my family the foods that our ancestors ate.. That includes meat, fat, dairy and eggs.. Our children are now middle-aged, older than many of their family who died young.. They are in good health with good cholesterol levels..

    Scientist can find anything they want and prove that it is bad for people, but when it comes to finding what is best to use for any given illness, guess what, getting ten scientist to agree on that subject is a million to one shot. People live until their expiration date, which becomes part of their lives when they are born. The fact that scientist cannot grantee how long any one will live proves that fact. The best statement they can come up with is; “people will live until they die!” However, some people are cut off from life through abortions, but they should know that was not in God’s plan where length of life is concerned. Life begins at conception whether people like it or not. It appears to me that most people believe that life is on some kind of auto-pilot, or something similar, but the Bible makes it clear that is not the truth. What does that book say?

    Psalm 104:27-30; “These wait all upon thee; that thou mayest give them their meat in due season. That thou givest them they gather: thou openest thine hand, they are filled with good. Thou hidest thy face, they are troubled: thou takest away their breath, they die, and return to their dust. Thou sendest forth thy spirit, they are created: and thou renewest the face of the earth.

    The entire dependence of this immense family on God is set forth from creatures in the sea. With Him, to kill or make alive is equally easy. To hide His face is to withdraw favor (Psalms 13:1). By His spirit, or breath, or mere word, He gives life. It is His constant providence which repairs the wastes of time and disease. However, while God can equally glorify His power in destruction, in His severity He can give death as easily as He gives life in preservation of His goodness and mercy, so that we may well spend our lives in grateful praise, honoring to Him, and delightful to pious hearts (Psalms 147:1). Paul tells us these things through his epistle to the Romans 11:22; “Behold therefore the goodness and severity of God: on them which fell, severity; but toward thee, goodness, if thou continue in his goodness: otherwise thou also shalt be cut off.”

    I am a Christian and so agree with the things that you have written, although I am confused about your applying this broad of a brush to the specific context of healthy eating. So with that as a baseline . . .

    There is one point on which I will disagree, namely

    “People live until their expiration date, which becomes part of their lives when they are born.” Really? Based on what other than you saying it?

    Any time I hear an extreme statement like this, I immediately question its validity. If there were truly an “expiration date”, then it would have very few component causes, such as death by disease or old age. Your statement includes every other causal effect as something set at birth that ultimately results in our expiration on a specific and lethal date. Nothing could be further from the truth.

    For example, take the case of someone who smoked from an early age, acquired lung cancer and died decades before when they would have died had they never smoked. Is that behavior programmed at birth? Were they unwilling accomplices in bringing about their demise on their expiration date, or did they make a poor choice and pay the price. Or is rampant obesity – the backdrop of this article – an overwhelming tool of fate that seals the doom of millions because they must die on their expiration date?

    What about the 70,000-odd people who have died each of the last several years because of opioid addiction – either purposeful or accidental? Or what of the person killed by the drunk driver? On the subject of car accidents, what about the young person who died after being struck by someone running the red light, a death mainly caused by just not looking before entering the intersection? Or what about someone who happened to be in the wrong place at the wrong time, like tourists killed in the tsunami events in the Far East in 2004? Or, for that matter, what of the countless number of people killed world-wide every year by Mother Earth with typhoons, tornadoes, rain/floods, lightning strikes, exposure, earthquakes, volcanic eruptions, etc? Many people who die are, metaphorically speaking, just drive-by shooting victims. Yet you have lumped all together in your better-felt-than-known pronouncement of this “Expiration Date” theory.

    The industrial revolution has certainly added huge number of causal deaths in its wake along with immeasurable benefits, one of them being extending lifespans. How does that fit into your thesis? There would be no death by electrocution, airplane / car / train crashes, building and bridge collapses, rocket launches and on and on if we still lived in the stone age. But if we did live in the stone age, neither would there be induced immunity from infectious diseases, or life-saving surgeries, or vastly decreased infant mortality, although there would be people dying en masse from polluted water and poor sanitary conditions, food poisoning due to no refrigeration, heat exhaustion due to lack of air conditioning, being kicked by a mule while plowing, ad infinitum.

    To use your terminology, there certainly is something that hastens one’s expiration date and that something is stupidity. The death-and-injury occurrence of young male drivers along with their high insurance rates is ample proof of that.

    Here’s another extreme statement that is broadcast as if it came from God Himself – “Everything happens for a reason”. That usually is quoted when something bad happens and we the search has begun for a silver lining. Stupidity is a big reason for bad things happening. The problem is that most people don’t want to own their own mistakes. It is far easier to say that “the universe is doing this to me” than to just say I messed up and now am bearing the pain for it. I have done some stupid things in my life, and have the scars to prove it. I own them all.

    In the metaphorical sense, we all certainly do have an expiration date as far as being mortal. To say that each of us has a date on which we will die and no one has any power over that date is foolish indeed.

    I would have to assume that he is a believer in the notion that God has a plan for each and every one of us the moment we are conceived. My only issue with that is if we are including outside extremities as “God’s Plan”, wouldn’t we have to include a terminated pregnancy in that grouping as well? I was born and raised Catholic. I am non-practicing, yet do not believe in abortion neither. I do not on the other-hand feel that our destiny is written at conception, and from what I can recall from 12 years of catholic schooling, neither does the church. I believe the teaching is that, while god does have “plans” per say, for each of us, it is up to us to live out this “plan”. But, it is by no means a pre-recorded outcome. But yea, why this discussion was started in an article about my favorite breakfast item is beyond me.

    You misunderstood the sentence. It just meant each of us will eventually die. It isn’t actually saying our date of death is predetermined.

    Life Begins At Breath. Abortion is a made up issue designed to coalesce a right-wing political movement. It isn’t even mentioned in the Bible unless you consider the obvious implications of the ordeal of the bitter water in Numbers 5. Everyone has a right to make their own decisions about abortion and we believe if someone is against it they shouldn’t have one. No one has the right to impose their beliefs on this topic on others, especially when right-wing Biblical interpretations are fabricated for political purposes. Genesis 2:7, He “breathed into his nostrils the breath of life and it was then that the man became a living being.” You need to get a grip brother, you losing it, right wing alternativechristians are spending billions of dollars a year on an anti abortion message. Just imagine if they spent that on the already living, for clean water, safe housing, better birthing practices, etc. Now please do me a favor. Since what we eat has nothing to do with how long we live, please come four cups of these night shade berries from out back of the barn and cook yourself up a divine little pie, sweeten it with honey and make a nice sugar crust!! Trust in God that all his fruit is good, and it is only an expiration date that will take you out. Peace and Love. You rationale is inspired by an indoctrination of hate and division, and it is very odd you feel such a need to THROW UP the abortion issue every single time you blog. Glory

    I have know knowledge about bacon and what it can or cannot do to you, not a fan.
    I am a seventy year old man and I can tell you I have eaten 2 egg every day most of my life. Lets say the first 10 years of my life I did not eat eggs and take 1 more year off for not having eggs for breakfast here and there over the 70 years. Now that leave 59 years of eating 2 eggs a day which work out to 43,070. So you would think I should be dead after eating all those eggs and that much cholesterol over the years.
    I have high blood pressure, high cholesterol, Diverticulitis, C.O.P.D, Asthma, Aortic Aneurysm, Arthritis, Sacroiliac joint pain, Fibromyalgia, Angina and Diabetes.
    I also had carpal tunnel in both arms. Appendicitis twice, first time it burst, Bladder Cancer, A foot and a half of my bowel removed.
    I know your saying this guy is full of shit or he should be dead and I would agree but I’m not, dead that is.
    I also had a angioplasty procedure to check my heart. The heart specialist were absolutely positive I had a heart attack. I was told my heart was as clean as a new born baby.
    I wonder about the high cholesterol the doctor said I have.
    The many doctors I have seen over the years said 2 egg a week is all you should eat it is bad for cholesterol.
    So do I believe egg are keeping my heart clean you bet your ass.
    I believe all the doctors were wrong about eggs
    I am not like the people they have study that can’t remember whether or not they ate eggs three days earlier. As I said earlier I am diabetic and I write everything down I eat and drink. So lady and gentlemen I would not take much stock in these scientific studies. There was a study done on cholesterol a few years back. They found there are two kind, good and bad cholesterol. The study said eggs have good cholesterol that kills the bad cholesterol which is fatty meats. I tend to believe there is good and bad cholesterol. I was not only an egg eater I was a lover of fat, so the good cholesterol in eggs must kill the bad cholesterol in fatty meats or I believe I would be dead years ago.

    Average person produces about 2000 mg of cholesterol a day. Average chicken egg has about 170 mg of cholesterol. If you eat 2 eggs in a given day your body should produce 340 mg fewer mg of cholesterol because it tries to keep cholesterol levels constant, not too high nor too low. This is normal, but there are people that are exceptions that fall towards extremes of normal curve due to genetics or their own particular differences. So there isn’t a one-size-fits-all in that a large study will provide an answer to all. Also, you might not know how scientifically thorough the study was performed. Best thing is do perform a sensitivity study of your own and see how consuming foods with cholesterol affect you personally and that will show up with blood lab results. Some people might not have to change anything and others might need to change foods, activity, other lifestyle changes. and/or take medications to control cholesterol.

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