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

    My great grandfather, a Mvskoke Creek Indian ate 6 eggs a day all his life and died at the age of 100. He was never sick a day in his life.

    My great grandfather, a Mvskoke Creek Indian ate 6 eggs a day all his adult life and lived to be 100 and was never sick a day of his life.

    My parents 89 and 90, and doing as well as expected. Dad has a number of issues due to Agent Orange exposure, but their outlook on eating their entire life has been “Everything in Moderation”. And so, I view eating the same way. I dont avoid anything, but never over-indulge either.

    Max has it right! My grandmother passed on to me the same exact words: “Everything in Moderation.” She said the words and lived them AND she taught me how to cook and bake fabulous food, not to lie or be wasteful and how to sew beautiful clothes!

    One major problem with this study is that dietary cholesterol has been shown to have no effect on cholesterol found in our systems.

    Dietary intake of cholesterol may have little or no effect on blood cholesterol levels. In my case this was true. With an extremely high blood cholesterol level my doctor recommended I go on a diet where all fats and products containing cholesterol were eliminated. After three months the effect was close to zero, even despite me taking the highest dose of Lipitor, Statin based cholesterol reducing drugs. Ironically, after reading a book titled the ‘Atkins Diabetes Revolution’ I changed my diet to the Atkins (anti diabetes) diet. My physician said ‘you have nothing to lose if you want to try a different approach’, which required me to eat more fats, proteins including plenty of eggs and other high cholesterol containing foods, while reducing to a minimum carbohydrates, especially the common ‘white’ carbs found in rice, flour and white breads, sugar and potatoes. After three months my doctor was amazed. Not only was my blood cholesterol normal (he took me off Lipitor), but my blood pressure had also come down and I no longer required medication for elevated blood pressure, all my other blood analysis results were perfect. I had lost about 5 Kg of body weight and felyt fitter than ever. I have now for over 15 years maintained a low carbs diet with no restriction on protein, fats or good carbs like green and red vegetables and reducing intake of sugar and ‘bad white’ carbs. My health remains excellent (I’m now 78 years of age and still doing the same things I used to do 25 years ago). So diets can work differently for different individuals. I ama good test case. But of course some individuals would likely have a very different outcome to mine.

    Arguments persist regarding human ingestion of eggs but researchers using rabbits have long standing, indisputable ways of inducing atherosclerosis in rabbits by what they feed them. How this translates to humans remains debatable. Plus, not all humans are alike. The same diet can produce significantly different levels of atherosclerosis in different individuals. Nutrition is an infant science for sure IMO.

    The problem with using rabbits in nutritional research is that they are obligate herbivores and therefore have no mechanism to deal with saturated fats found in animal products. It’s like putting diesel in a standard car engine and concluding that diesel makes a terrible fuel and should be outlawed.

    This has been the biggest shit show I’ve ever read.

    Has anyone done a study on fertilized chicken eggs?

    Also 150 year ago when bacon and eggs was a way to keep your heart lubricated, but only if you could afford it. If you could afford bacon and eggs you probably didn’t get infection from cuts while shoveling horse shit.

    So yes eggs are definitely good for you if you can afford them.

    I agree with you that 150 years ago only the wealthy could afford to eat bacon and eggs on a regular basis. However, you say that eating bacon and eggs was a way to keep your heart lubricated. Why do you think that eating bacon and eggs keeps your heart lubricated? You also say that eating bacon and eggs reduced the likelihood that cuts would become infected. Why do you think that regularly eating bacon and eggs reduced the likelihood of infection?

    Thank You ! Excellent work.
    Shut up nay sayer’s. What work have YOU put in to this study ? NONE.

    You claim that if someone did not put any work into the study, then they have no right to criticize that study. That makes absolutely no sense. Suppose that someone writes an essay on how planet earth is as flat as a pancake, or an essay on how bacteria do not exist. Also, assume that you did not help them write that essay. You did not put any work yourself into the essay on how bacteria don’t exist. That does not mean that your criticism of their essay in somehow invalid. The study on eggs tracked participants’ health outcomes for at least 13 years. Participants were asked about their diet only once, at the beginning of the study. Lots of people change their diet. A lot of people probably did not eat the same thing 10 years later as when the study was started. That a legitimate criticism, even if the critic never helped work on the study.

    My maternal grandfather, born in Italy, had a raw egg in a shot of whiskey most mornings for breakfast and said it was an old world remedy for a long life. He was extremely healthy till the last year of his life (died at 94). He seldom drank more than a glass of wine with dinner, otherwise.

    My maternal step-grandfather, Fortunato, also from Italy, had the same egg and whiskey routine as your grandfather did every morning. I recall in his later years, Nona cracking a raw egg in a brandy glass for him every morning before he went out to work in the family garden. (It was an immense garden.) He claimed that his ‘breakfast’ was the secret behind his good health and longevity. He could still climb trees in his seventies and lived to be 98.
    I tried this routine in my early twenties for three days. On the third day, while in a daze at my drafting table, it dawned on me that I was showing up to work drunk. The experiment ended there. Now in my later years, I am thinking about giving it another shot.
    Ken, thanks for rekindling the good memories!

    George Bedell

    What I find funny is when people discuss weight loss or gain it’a always food fault. How about sitting on the couch and binge watching mind numbing things. Imagine if one of those hours these do-no-exercise humans got up and burned these calories and increased their metabolism? How much discussion would we need about diet?

    Speaking of the requirement to exercise for healthy and successful weight loss, a theory that is ‘believed’ by nearly everyone, I have found that exercise makes no difference whatsoever to weight loss while dieting. I lose weight well when I diet properly. I aim for 2 lbs a week and nearly always reach that. If I were to try to exercise (or move strenuously) enough to actually burn off enough calories to have an affect I would have to do SO much of that that I’d have to quit many or some of the things I do daily that are part important parts of my life. I have never ever seen any difference in weight loss when I am more active vs less.
    I read a study a few years ago that stated clearly that activity level, described as ‘exercise’, made no difference in weight loss. Since I already believed that, I believed the study findings.
    My point is that perhaps for some people exercise can affect weight loss (and metabolism) but it certainly does NOT affect ALL people, and I am one example of that. I am healthy and slim. I diet successfully. I do it all as I move normally doing normal things that are NOT considered strenuous or athletic. I don’t like to sweat and refuse to deliberately impose that upon myself.
    So, I wish that the athletic people would recognize that bodies are ALL different and that their method is not necessarily the right thing for others.

    Perhaps exercise is less important for weight loss, though I would argue that a certain amount would contribute to a certain degree, exercise is very important for overall health. Keeping your weight under control is important, but keeping fit is equally if not more important. Wouldn’t you agree?

    Eggs as a source of protein are cheaply available and best of all they are portion controlled. Arguably in the western world’s over-large portions and lack of fiber are our #1 and #2 problems (unless you want to count lack of exercise). At only 70 calories for a large egg, eggs are great. I’m 53 and my cholesterol always comes in low. Any food study should account for how eggs are cooked (fried anything is less healthy). It should also account for what is eaten with it–as much as I like bacon or sausage, bacon and sausage are processed foods (usually fried). Instead of telling people not to eat eggs, we would be better off to tell people to cut (or cut back on) processed foods–such as bacon. Also, we should reconsider how we eat our 1 or 2 eggs. If we have one egg on toast–get the 3 grams of fiber, 60 calorie bread. If we eat two eggs–because we are really hungry–then we should be putting our eggs in a salad or scrambling our eggs in a cooked cabbage/carrots/kale salad bowl so that we get the daily recommended amount of fiber. Then afterwards, go for a walk.

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