Nutrition studies are like that one person you know who says one thing one moment and then turns around and says the complete opposite. Coffee can disrupt your sleep and give you some unpleasant gut problems, but on the other hand, drinking a few cuppas will extend your life. Wine has the perplexing capability of both extending and shortening one's life. And chocolate goes between sugar villain to "one square a day" cult status (which in itself is baffling, what normal human stops at just one square of chocolate?).
But nothing has created quite the stir and volleying between good and bad than eggs.
On an economic and baseline nutritional level, eggs are a superfood. They're cheap—a dozen eggs can usually be purchased for under a couple bucks—and they're plentiful. They're packed with protein and vitamins and minerals that have earned the egg glowing reviews. And they can be imagined into countless forms: scrambled, poached, over and easy, hard boiled, egg cetera egg cetera.
But David Spence, a professor of neurology at the University of Western Ontario, vehemently disagrees with the egg's vaulted status as a nutritional superstar. For years, he's run a stroke prevention clinic while researching atherosclerosis, the medical term for artery walls getting piled up with gunk (like fat and cholesterol) and narrowing the tunnel through which blood can flow. If arteries get clogged, strokes and heart attacks can occur.
The best way to stop atherosclerosis from taking full form is diet, and Spence's research highlights why we've gone back and forth on whether eggs are good or bad for so long. He's authored papers that show the connection between egg yolks and carotid plaque, which can cause heart disease, going so far as to suggest that they are comparable to smoking ("The exponential nature of the increase in TPA [total plaque area] by quintiles of egg consumption follows a similar pattern to cigarette smoking"). Spence has penned letters such as this one in the journal Atherosclerosis in 2013 saying that while egg yolks are key to cooking and can be nutritious, most Western societies don't suffer from malnourishment that would make eating eggs daily necessary or healthy. He's written paper after paper about how eggs are associated with vascular disease.
To Spence, who has not had an egg yolk in 40 years, the fact that eggs have seen a renaissance of sorts as a perfect food is troubling and indicative of the "propaganda of the egg industry." Spence said the American diet veers toward being higher in cholesterol and fat, and that that has been accentuated by food lobbies that have encouraged the consumption of foods like eggs. He cited the December 1976 decision by the Federal Trade Commission that called the National Commission on Egg Nutrition's calling egg a healthy food misleading ("There's a lot of money in eggs"), but that the cultural impact of eggs as part of a nutritious breakfast as permanent and problematic.
"It's been so hard to show the harm from eggs in the United States," Spence told The Daily Beast, saying that pop culture's insistence that an egg formed a normal part of a breakfast means that it's been hard to change popular opinion about eggs being potentially bad for health. "If you feed your children eggs, they're going to grow up with the idea that eggs are enjoyable."
While eggs are often described as a great source of protein, Spence said that the Mediterranean diet that is heralded as the best for its nutritional benefits, long livelihood, and vegetable-heavy diet, doesn't look at egg yolks as a good source of protein but rather egg whites. "Egg whites are fine but they're boring," he admitted, though he suggested that egg white substitutes had made advances in flavor.
"There's no controversy at all [as to whether eggs are good or bad]," Spence said. "People think eggs are good because of the marketing of the American Egg Board, which gives out $200,000 grants to fund studies." Spence said that some of his research has been attacked by the AEB. (Spence said his studies are primarily funded by heart and stroke foundations, his university, and groups promoting the reduction of cholesterol.)
Tia Rains, however, disagrees. She's the executive director of the egg nutrition center at the American Egg Board, so one can say she's got skin in the game. Rains admitted that the AEB has interests in promoting eggs—but argued that the Board's following of government health guidelines mean that it's not just hawking eggs. "We're a research and promotion board," she said. "We fall under the USDA. We follow all the public health guidelines with respect to eggs. Part of our mandate, which is an act of Congress, is to do research on our product, so we yes, we do fund research on eggs. But the hope is that other people will do research on eggs as well, and look into other pots of money [that aren't associated with the AEB] and have similar results regardless of the funding source."
Rains said that the board doesn't believe the cholesterol content of eggs detracts from the nutritional potential of eggs—against Spence's studies—because it's simply following the American Health Association and American College of Cardiology's recommendations in 2013 that did not include a cholesterol cap. Previous reports from the AHA and ACC had suggested that eating more than 300 mg of cholesterol per day was not advised.
In fact, those guidelines launched a debate within nutritional and medical communities at the time, with some suggesting that the government was spewing out "bad" dietary advice, but the ACC came back with a bit on eggs and why the group was arguing that paying attention to eggs and their cholesterol levels was problematic:
"Each large egg contains about 186 mg of cholesterol. Therefore, someone who averages one egg daily and consumes additional meat, fish, poultry, or dairy products cannot meet the 200 mg per day cap recommended in those guidelines that currently include cholesterol limits. Since cholesterol content does not decrease proportionately with fat content, this is true even if additional animal-based foods are lean. Overall, prospective cohort studies do not support a link between egg consumption and risk of cardiovascular events or mortality. Moreover, a controlled interventional trial showed no effect of daily egg consumption on endothelial function in adults with coronary artery disease. Thus, although setting a limit on dietary cholesterol requires a limit on egg consumption, evidence showing benefit of reduced consumption of eggs appears lacking."
To Rains, this movement of considering eggs as a more "holistic" part of a diet is something most nutritional organizations have been working towards over the past few years, as we veer away from the 90s era nonfat craze that saw the rise—and now downfall—of skim milk, margarine, and yes, eggs. To her, and to many nutritionists who now say that the shunning of fat in foods was problematic and encouraged the rise of chemical additives often tied to cancer, eggs are emblematic of the dietary pattern approach that the AHA has adopted in considering the whole diet and thinking about variety as key, and the overall focus on cholesterol draws attention from positive aspects of eggs.
"The overall dietary pattern matters," she stressed. "In large public health organizations that evaluate data like this, they've found insufficient evidence time and time again that dietary cholesterol is a tool for lowering blood cholesterol. Individual studies have shown this as well as meta analyses. We didn't know about the positive aspects of eggs for years because scientists were focused on only cholesterol." She said now the egg had been "exonerated," and that "we're going to start to see some really interesting data come around, especially in infants and children and as a solution for malnutrition."
Ironically, Spence repeatedly said in his conversation with The Daily Beast that the only people who should be having whole eggs are "starving children ... suffering from malnutrition." Spence also finds the new dietary regulations to be dangerous in having no cap on cholesterol and its focus on "eating patterns." "It's not safe to eat eggs, especially for those who have vascular disease, and the new guidelines say it's okay to not have a number for cholesterol," he said. "That might lead to a risk of diabetes, heart attacks, and strokes."
But Rains also said that eggs have repeatedly been shown to be good for you, arguing that the "cholesterol science has evolved over the past 40 years." "Numerous papers show no association with heart disease," she said. "Eggs might even reduce the chance of stroke."
When asked if the yolk should be discarded, as Spence suggested, she vehemently said no. "That's where the nutrient of the egg is, the yolk," she said. "There are nutrients like riboflavin and lutein, which is a caratinoid that has been linked to brain health. Two-thirds of the protein lives in the yolk. And it also has choline, which is emerging as a critical nutrient for infants and the elderly."
But Rains stopped short of recommending eggs as a blanket "good for you" food. "There's always individual variations so it's hard to make a sweeping statement," she said. "The standard dietary recommendation of the AHA is to have lots of fruits and vegetables, and layer on lean sources of protein." Rains said that while she considered eggs to be a nutrient powerhouse, there's work to be done on transforming them into a food that isn't necessarily paired with other fatty and cholesterol-laden breakfast foods like bacon, potatoes, and white bread slathered in butter. "They're a great match with vegetables, avocados, and grains, and you can have eggs any time of day," she said, pointing to the normal reputation of eggs being relegated to breakfast. "What makes eggs so great is that they can be eaten any time and give you satiety, that feeling of being full."
Ok, you might say: This still doesn't answer the question. Are eggs good or bad for you, once and for all?
The unsatisfying answer to that is that there's no right answer and that each individual's unique health needs and genetic history are such that they should be monitored with the help of a physician and maybe even a dietician.
Eggs and their confusing Dr. Jekyll and Mr. Hyde nutritional personas—along with those of many other foods who are deigned to be health superstars one moment and the equivalent of poison the next—are emblematic of the huge, glaring flaw in nutritional studies: their reliance on epidemiological cohort studies. Food scientists aiming to answer a seemingly straightforward question—"Is x good/bad for you?"—follow large groups of people eating the food in question for years, monitor their pertinent nutritional levels, and, based on what the litany of physical reports suggest, make some vague conclusion that a food can extend one's life or make one more productive or, alternatively, bring about a person's untimely demise.
But cohort studies are poor indicators of what to do and what not to do simply because they don't necessarily prove anything. They might show that the protein of eggs for breakfast can stave off hunger for raiding the office candy cabinet, or that the choline found in eggs is associated with brain development, but they can't show that eggs actually cause these things. Plus, the food industry is intertwined with studies—Spence repeatedly mentions the egg lobby's role in promoting eggs, but such lobbying also extends to other foods, notoriously sugar—and it becomes nearly impossible to discern if an egg is good or bad for you.
That said, there is actually an answer as to whether or not eggs are good for you, though it's frustratingly opaque and wishy-washy: Egg whites are universally heralded by Spence and Rains and other experts along the egg nutrition spectrum as not only safe for cholesterol watchers and those at risk of cardiovascular diseases, but also healthy with their lack of fat and ringing in at 17 calories.
The yolk, on the other hand? Its nutritional benefits—or lack thereof—is something that Spence, Rains, and the rest of the medical and nutritional community continue to duke out on, and probably will for a long time to come.