Last summer time, I obtained a tip a few curious scientific discovering. “I’m sorry, it cracks me up every time I think about this,” my tipster stated.
Back in 2018, a Harvard doctoral scholar named Andres Ardisson Korat was presenting his analysis on the connection between dairy meals and power illness to his thesis committee. One of his research had led him to an uncommon conclusion: Among diabetics, consuming half a cup of ice cream a day was related to a decrease danger of coronary heart issues. Needless to say, the concept that a dessert loaded with saturated fats and sugar may really be good for you raised some eyebrows on the nation’s most influential division of diet.
Earlier, the division chair, Frank Hu, had instructed Ardisson Korat to do some additional digging: Could his analysis have been led astray by an artifact of likelihood, or a hidden supply of bias, or a computational error? As Ardisson Korat spelled out on the day of his protection, his debunking efforts had been largely futile. The ice-cream sign was strong.
It was strong, and sort of hilarious. “I do sort of remember the vibe being like, Hahaha, this ice-cream thing won’t go away; that’s pretty funny,” recalled my tipster, who’d attended the presentation. This was clearly not what a budding diet knowledgeable or his super-credentialed committee members had been hoping to find. “He and his committee had done, like, every type of analysis—they had thrown every possible test at this finding to try to make it go away. And there was nothing they could do to make it go away.”
Spurious results pop up on a regular basis in science, particularly in fields like dietary epidemiology, the place the well being considerations and dietary habits of a whole bunch of 1000’s of individuals are tracked over years and years. Still, the abject silliness of “healthy ice cream” intrigued me. As a public-health historian, I’ve studied how groups of researchers course of information, mingle them with principle, after which bundle the outcomes as “what the science says.” I needed to know what occurs when consensus makers are confronted with a discovering that appears to contradict all the pieces they’ve ever stated earlier than. (Harvard’s Nutrition Source web site calls ice cream an “indulgent” dairy meals that’s thought of an “every-so-often” deal with.)
“There are few plausible biological explanations for these results,” Ardisson Korat wrote within the temporary dialogue of his “unexpected” discovering in his thesis. Something else grabbed my consideration, although: The dissertation defined that he’d hardly been the primary to look at the shimmer of a well being halo round ice cream. Several prior research, he recommended, had come throughout an analogous impact. Eager to study extra, I reached out to Ardisson Korat for an interview—I emailed him 4 occasions—however by no means heard again. When I contacted Tufts University, the place he now works as a scientist, a press aide informed me he was “not available for this.” Inevitably, my curiosity took on a special shade: Why wouldn’t a younger scientist wish to discuss with me about his analysis? Just how a lot deeper may this weird ice-cream factor go?
“I still to this day don’t have an answer for it,” Mark A. Pereira, an epidemiologist on the University of Minnesota, informed me, talking of the affiliation he’d stumbled upon greater than 20 years earlier. “We analyzed the hell out of the data.”
Just that morning, I’d been studying one among Pereira’s early papers, on the well being results of consuming dairy, as a result of it appeared to have impressed different analysis that was cited in Ardisson Korat’s dissertation. But once I scrolled to the underside of Pereira’s article, down previous the headline-making conclusions, I noticed in Table 5 a set of numbers that made me gasp.
Back then, Pereira was a younger assistant professor at Harvard Medical School. Hoping to handle the newly labeled epidemics of weight problems and diabetes, he initially targeted his analysis on bodily exercise, however quickly turned to the unsettled science of wholesome consuming. The standing of dairy, specifically, was slowed down in simplistic and competing assumptions. “We just thought, Oh, you know, calcium and bones: It’s good for kids. But, oh, the saturated fat! Don’t eat too much dairy! ”
Pereira and his co-authors examined these previous concepts utilizing information from a research, begun in 1985, that tracked the emergence of heart-disease danger elements in additional than 5,000 younger adults. After seeing the outcomes, “we knew it was going to be very high-profile and controversial,” Pereira recalled. Pretty a lot throughout the board—low-fat, high-fat, milk, cheese—dairy meals appeared to assist forestall obese individuals from growing insulin-resistance syndrome, a precursor to diabetes. “I’ll tell you, this study surprised the heck out of me,” stated one CNN correspondent, as Pereira’s research spiraled via the press.
But the worldwide media protection didn’t point out what I’d seen in Table 5. According to the numbers, tucking right into a “dairy-based dessert”—a class that included meals similar to pudding however consisted, in response to Pereira, primarily of ice cream—was related for obese individuals with dramatically lowered odds of growing insulin-resistance syndrome. It was by far the largest impact seen within the research, 2.5 occasions the dimensions of what they’d discovered for milk. “It was pretty astounding,” Pereira informed me. “We thought a lot about it, because we thought, Could this actually be the case? ”
There had been causes to be cautious: The information set wasn’t enormous, in epidemiological phrases, and contributors hadn’t reported consuming that many dairy-based desserts, so the margin of error was large. And provided that the research’s general message was positive to draw criticism—Pereira recalled getting “skewered” by antidairy activists—he had little want to make a fuss about ice cream.
Pretty quickly, Pereira’s friends discovered themselves in the identical predicament. Building on the 2002 research and the rising curiosity in dairy, researchers on the Harvard School of Public Health determined to interrupt out a few of their strongest instruments. Since the Nineteen Eighties, Harvard’s scientists have been accumulating “food-frequency questionnaires” and medical information from many 1000’s of nurses, dentists, and different health-care employees. These world-famous research have fueled a stream of influential findings, together with among the information that sparked the elimination of trans fat from the meals provide.
The outcomes of Harvard’s first observational research of dairy and sort 2 diabetes got here out in 2005. Based on information collected from simply one among their three cohorts, following males between 1986 and 1998, the authors reported that larger dairy consumption, and better low-fat-dairy consumption specifically, was related to a decrease danger of diabetes. “The risk reduction was almost exclusively associated with low-fat or non-fat dairy foods,” a Harvard information bulletin defined. An article on Fox News’s web site underscored the low-fat message: “There was no decrease in men who drank whole milk,” the story stated.
Perhaps not entire milk, however what about butter pecan? Near the top of the Harvard paper, the place the authors had arrayed the diabetes dangers related to numerous dairy meals, was a discovering that was barely talked about within the “almost exclusively” low-fat narrative given to reporters. Yes, in response to that desk, males who consumed two or extra servings of skim or low-fat milk a day had a 22 p.c decrease danger of diabetes. But so did males who ate two or extra servings of ice cream each week. Once once more, the information recommended that ice cream is likely to be the strongest diabetes prophylactic within the dairy aisle. Yet nobody appeared to wish to discuss it.
In the years that adopted, analysis summaries generally agreed that excessive dairy consumption general was associated with a barely lowered danger of diabetes, however referred to as for extra investigation of which particular dairy meals may need the best advantages. In 2014, Harvard’s diet workforce introduced one other dozen years of diet-tracking information to bear on this query. In this new research, complete dairy consumption now appeared to haven’t any impact, however the ice-cream sign was inconceivable to overlook. Visible throughout a whole bunch of 1000’s of topics, all of it however screamed for extra consideration.
Following a sample of incredulousness that was by then greater than a decade previous, Frank Hu, the research’s senior writer and the longer term chair of Harvard’s diet division, requested the graduate scholar who’d led the mission, Mu Chen, to double-check the information. “We were very skeptical,” Hu informed me. Chen, who’s now not in academia, didn’t reply to interview requests, however Hu recalled that no errors within the information may very well be discovered.
The Harvard researchers didn’t just like the ice-cream discovering: It appeared mistaken. But the identical paper had given them one other end result that they appreciated a lot better. The workforce was going all in on yogurt. With a rising repute as a boon for microbiomes, yogurt was the anti-ice-cream—the wholesome particular person’s dairy deal with.
“Higher intake of yogurt is associated with a reduced risk” of kind 2 diabetes, “whereas other dairy foods and consumption of total dairy are not,” the 2014 paper stated. “The conclusions weren’t exactly accurately written,” acknowledged Dariush Mozaffarian, the dean of coverage at Tufts’s diet college and a co-author of the paper, when he revisited the information with me in an interview. “Saying no foods were associated—ice cream was associated.”
But yogurt made a lot extra sense. In a approach, it was affirmation of one thing that everybody already knew. From the beginning of yogurt’s entrée into the American food plan, it had been perceived as an unique meals from a faraway land, quivering with obscure health-giving properties. Even after being spiked with sugar within the ’70s and ’80s to raised go well with the U.S. market, yogurt nonetheless retained its picture as an elixir.
Furthermore, a rising physique of literature recommended that yogurt’s well being advantages is likely to be actual. Harvard had discovered, just a few years earlier, that consuming yogurt was associated with lowered weight acquire; researchers on the college had been all for its doable results on intestine micro organism as effectively. Other research—together with people who first revealed the ice-cream sign—had additionally sketched the slender outlines of a yogurt impact. When Chen and Hu pooled collectively findings from this analysis, added of their newest information, and carried out a meta-analysis, they concluded that yogurt was certainly related to a lowered danger of diabetes—a possible profit, they wrote, that warranted additional research.
Regarding ice cream’s potential advantages, they’d a lot much less to say. I requested different specialists to match the 2014 yogurt and ice-cream findings. Kevin Klatt, a diet scientist at UC Berkeley, stated the ice-cream impact was “more consistent” than yogurt’s throughout the studied cohorts. Deirdre Tobias, an epidemiologist at Harvard, the tutorial editor of The American Journal of Clinical Nutrition, and a member of the advisory committee for the 2025 replace to the U.S. dietary pointers, agreed with that evaluation. Even Dagfinn Aune, an epidemiologist at Imperial College London and a peer reviewer of the Chen and Hu paper, stated that the ice-cream impact was “similar” in magnitude to, or “slightly stronger” than, the one for yogurt.
So how did the Harvard workforce clarify away the ice-cream discovering? The principle went like this: Maybe among the individuals within the research had developed well being issues, similar to hypertension or elevated ldl cholesterol, and commenced avoiding ice cream on docs’ orders (or of their very own volition). Meanwhile, individuals who didn’t have these well being issues would have had much less purpose to surrender their cookies and cream. In that situation, it wouldn’t be that ice cream prevented diabetes, however that being prone to growing diabetes induced individuals to not eat ice cream. Epidemiologists name that “reverse causation.”
To check this concept, Hu and his co-authors put aside dietary information collected after individuals obtained these types of diagnoses, after which redid their calculations. The ice-cream impact shrank by half, although it was nonetheless statistically vital, and nonetheless larger than the low-fat-dairy impact that Harvard had publicized in 2005. In any occasion, if individuals who obtained hostile diagnoses in the reduction of on their ice cream, you may anticipate that they’d additionally in the reduction of on, say, cake and doughnuts. So shouldn’t there be mysterious protecting “effects” for cake and doughnuts too? “There should be,” Mozaffarian stated. “That’s why the finding for ice cream is intriguing.”
The new evaluation was hardly a slam dunk. On paper, the yogurt and ice-cream results nonetheless appeared fairly related. “Within the realm of statistical uncertainty, they’re identical,” Mozaffarian informed me. But within the 2014 paper, he and the opposite authors had argued that “reverse causation may explain the findings” for ice cream. And as academia’s public-relations equipment got here to life, nuance went out the window.
“Does a yogurt a day keep diabetes away?” requested the press launch that went out on publication day. “Other dairy foods and consumption of total dairy did not show this association,” stated Hu, the senior writer, in an ice-cream-free appraisal included within the launch and echoed in Harvard’s personal press bulletin. “Yogurt has approached wonder-food status in recent years,” a Forbes article on the paper famous. “In the new study, other forms of dairy like milk and cheese, did not offer the same kind of protection as yogurt.”
Hu says at this time that the Harvard researchers felt assured of their conclusions about yogurt largely on account of their meta-analysis, and the truth that prior scientific research and fundamental science analysis supported the concept that probiotics enhance metabolic outcomes. “For ice cream, of course, there is no prior literature,” he stated. Given that the ice-cream impact was diminished after they examined their reverse-causation principle, he referred to as it “much more plausible” that yogurt would assist forestall diabetes than ice cream.
After his paper was revealed, it didn’t take lengthy for the Harvard group’s excellent news about yogurt to take maintain as a dominant scientific narrative. Two years later, when a workforce of researchers based mostly within the Netherlands and at Harvard analyzed all of the proof it may discover on dairy and diabetes, the yogurt impact popped out. A featured graph from the workforce’s 2016 paper in The American Journal of Clinical Nutrition summarizes information from a few dozen research: As somebody’s yogurt consumption mounts to roughly one-third of a cup a day, their danger of getting diabetes shrinks by 14 p.c.
The authors additionally discovered the ice-cream impact: Consuming as little as a half a cup per week was related to a 19 p.c lowered diabetes danger. But that discovering’s epitaph was already written. The researchers concluded that consuming “dairy foods, particularly yogurt,” may assist curb the diabetes epidemic, and famous that the advantages of ice cream had elsewhere been written off as a product of reverse causation. The proof in yogurt’s favor was a lot better established, Sabita Soedamah-Muthu, an epidemiologist at Tilburg University and the paper’s senior writer, informed me. The ice-cream impact had fewer research in its nook. “We didn’t believe in it,” she stated.
There’s a factor that occurs while you begin writing a narrative about how perhaps, probably, consider it or not, ice cream is likely to be kind of good for you, and the way among the world’s high nutritionists gathered proof supporting that speculation however discovered causes to look previous it. You start to ask your self: Am I excessive by myself ice-cream provide? I requested the specialists for a intestine verify. Pereira, the primary to stumble on the ice-cream impact, informed me that it simply wasn’t the sort of end result that goes down effectively within the “closed-minded” world of elite diet. “They don’t want to see it. They might ponder it for a second and kind of chuckle and not believe it,” he stated. “I think that’s related to how much the field of nutritional epidemiology in the modern era is steeped in dogma.” Tobias, the journal editor and member of the 2025 U.S. dietary-guidelines advisory committee, referred to as it “totally fair criticism” to ask why yogurt was performed up whereas ice cream was performed down. She expressed assist for the Harvard workforce’s dealing with of the information, whereas acknowledging the tensions concerned: “You don’t want to overstate stuff that you know probably has a high likelihood of bias, but you also don’t want to do the opposite and seem to be burying it, either.”
Hu, the Harvard nutritionist, stated that deciding what a research means requires wanting past the numbers to what’s already recognized about dietary science: “You need to interpret the data in the context of the rest of the literature.” Mozaffarian, Hu’s co-author, echoed this view. Still, he famous, “you’re raising a really, really important point, which is that when, as scientists, we find things that don’t fit our hypotheses, we shouldn’t just dismiss them. We should step back and say, ‘You know, could this actually be true?’ ”
Could the concept that ice cream is metabolically protecting be true? It could be fairly bonkers. Still, there are at the very least just a few factors in its favor. For one, ice cream’s glycemic index, a measure of how quickly a meals boosts blood sugar, is decrease than that of brown rice. “There’s this perception that ice cream is unhealthy, but it’s got fat, it’s got protein, it’s got vitamins. It’s better for you than bread,” Mozaffarian stated. “Given how horrible the American diet is, it’s very possible that if somebody eats ice cream and eats less starch … it could actually protect against diabetes.” The “Got Milk?” crowd additionally loves to speak in regards to the “milk-fat-globule membrane,” a triple-layered organic envelope that encases the fats in mammalian milk. Some proof suggests that dairy merchandise by which the membrane is unbroken, similar to ice cream, are extra metabolically impartial than meals like butter, the place it’s misplaced through the churn. (That stated, common cream has an intact membrane, and it hasn’t been persistently related to a lowered diabetes danger.)
Then there may be what may charitably be termed the “real-world evidence.” In 2017, the YouTuber Anthony Howard-Crow launched what Men’s Health referred to as “a diet that would make the American Dietetic Association shit bricks”: 2,000 energy a day of ice cream plus 500 energy of protein dietary supplements plus booze. After 100 days on the ice-cream food plan, he’d misplaced 32 kilos and had higher blood work than earlier than he’d began pounding Irish-whiskey milkshakes. Still, the tactic is unlikely to take the slimming world by storm: Howard-Crow referred to as his ice-cream bender “the most miserable dieting adventure I have ever embarked upon.”
But general, I discovered extra receptiveness to the ice-cream sign than I used to be anticipating. “It’s been more or less replicated,” Pereira famous. “Whether it’s causal or not still remains an open question.” Mozaffarian agreed: “I think probably the ice cream is still reverse causation,” he stated. “But I’m not sure, and I’m kind of annoyed by that.” If this had been a patented drug, he continued, “you can bet that the company would have done a $30 million randomized controlled trial to see if ice cream prevents diabetes.”
To be clear, not one of the specialists interviewed for this text is inclined to consider that the ice-cream impact is actual, though typically for causes that differ from Hu’s. Pereira, for instance, identified that individuals aren’t at all times truthful after they’re quizzed on what they eat. His 2002 research discovered that obese and overweight individuals reported consuming fewer dairy-based desserts than different individuals. “I don’t believe that the heavier people consume less desserts,” he stated. “I believe they underreport more.” If that’s true, then admitting to consuming ice cream may correlate with metabolic well being—and the ice-cream impact could be, in its approach, a marker of fats stigma in America.
The downside with this line of pondering is that after you begin considering all of the ways in which cultural biases can seep into the science, it doesn’t cease at dairy-based desserts. If the ice-cream impact will be put aside, how ought to we take into consideration different indicators produced by the identical analysis instruments? “I don’t know what I believe about yogurt,” Tobias informed me. It’s broadly recognized that yogurt eaters on common are more healthy, leaner, wealthier, higher educated, extra bodily lively, extra prone to learn labels, extra prone to be feminine, and fewer prone to smoke or drink or eat Big Macs than never-yogurters. “You can’t confidently adjust away all of that kind of stuff,” stated Klatt, the UC Berkeley nutritionist.
In 2004, the English epidemiologist Michael Marmot wrote, “Scientific findings do not fall on blank minds that get made up as a result. Science engages with busy minds that have strong views about how things are and ought to be.” Marmot was writing about how politicians cope with scientific proof—at all times concluding that the newest information supported their present views—however he acknowledged that scientists weren’t so totally different.
The ice-cream saga reveals how this performs out in observe. Many tales will be informed about any given scientific inquiry, and selecting one is a messy, value-laden course of. A scientist could fear over how their story matches with widespread sense, and whether or not they have adequate proof to again it up. They can also fear that it poses a menace to public well being, or to their credibility. If there’s a lesson to be drawn from the parable of the food plan world’s most inconvenient fact, it’s that scientific information is itself a packaged good. The information, no matter they present, are simply components.
This article seems within the May 2023 print version with the headline “The Ice-Cream Conspiracy.”