MENU

Reason.com

Free Minds & Free Markets

Most Nutrition Research Is Bunk

Implausible estimates of benefits or risks associated with diet reflect almost exclusively the magnitude of nutrition researchers' cumulative biases.

FoodGroupsCharnalakSuwannateDreamstimeCharnalak Suwannate/DreamstimeGovernment nutrition advice based on decades of "research" by nutrition epidemiologists has now been shown to be mostly unwarranted scaremongering, writes Stanford University statistician John P.A. Ioannidis, who has been at the forefront of criticizing the misuse and abuse of statistics to justify the publication of shoddy and just plain wrong research in numerous disciplines.

In his justly famous 2005 PLoS Medicine article, "Why Most Published Research Findings Are False," Ioannidis concluded that "for many current scientific fields, claimed research findings may often be simply accurate measures of the prevailing bias." As the co-director of the Meta-Research Innovation Center at Stanford (METRICS) Ioannidis has turned his attention to what passes for nutrition science in a recent analysis, "The Challenge of Reforming Nutritional Epidemiologic Research," in the Journal of the American Medical Association.

As an example of how badly nutritional research violates good scientific principles, Ioannidis parses the results of a recent meta-analysis of nutritional studies that aimed to "synthesize the knowledge about the relation between intake of 12 major food groups, including whole grains, refined grains, vegetables, fruits, nuts, legumes, eggs, dairy, fish, red meat, processed meat, and sugar-sweetened beverages, with risk of all-cause mortality."

In his critique of the meta-analysis, Ioannidis points out, "Assuming the meta-analyzed evidence from cohort studies represents life span–long causal associations, for a baseline life expectancy of 80 years, nonexperts presented with only relative risks may falsely infer that eating 12 hazelnuts daily (1 oz) would prolong life by 12 years (ie, 1 year per hazelnut), drinking 3 cups of coffee daily would achieve a similar gain of 12 extra years, and eating a single mandarin orange daily (80 grams) would add 5 years of life. Conversely, consuming 1 egg daily would reduce life expectancy by 6 years, and eating 2 slices of bacon (30 g) daily would shorten life by a decade, an effect worse than smoking." These inferences are implausible to say the least.

So what is going on here? Most nutrition research are observational studies that often rely on surveys in which participants unreliably recall what they eat. And since eating is a complex activity researchers are very likely to miss confounding data that would call their epidemiological speculations into question.

Consider the notorious 1981 Harvard study that found that drinking coffee was associated with a higher risk of pancreatic cancer. The effect entirely disappeared when the confounder of smoking was taken into account. As it happens, a 2016 meta-analysis found that "high coffee consumption is associated with a reduced pancreatic cancer risk." Ioannidis is surely right that pervasive nutritional research flip-flops "may have adversely affected the public perception of science."

Instead of performing yet more dodgy observational studies, Ioanndis suggests that "large-scale, long-term, randomized trials on nutrition may be useful." And yet he immediately follows up with a devastating critique of a prominent recent study that purportedly identified beneficial effects from eating a so-called Mediterrean diet.

The Prevención con Dieta Mediterránea (PREDIMED) study supposedly compared three randomized groups: the first was given free supplies of extra virgin olive oil; another a supply of mixed nuts; and the third a bit of advice on what constituted a Mediterranean diet. The researchers were aiming to see if there were any significant differences with regard to the incidence of heart attacks and strokes between the groups.

The initial publication did find some beneficial effects from consuming olive oil and nuts. However it had to be withdrawn and re-analyzed after outside researchers showed that it was actually not randomized. The rejiggered study still found that eating nuts and olive oil reduced by a tiny amount the risk of experiencing a cardiovascular event. On the other hand, there was essentially no difference between the groups with respect to the risk of dying from any cause.

Ioannidis calls for reforming the field of nutritional epidemiology by adopting such measures as requiring that researchers make all of their data available for re-analysis by independent investigators and that results should be presented in their totality for all nutritional factors measured.

Until nutritional epidemiology is radically reformed, we should all keep in mind Ioannidis' observation that the "implausible estimates of benefits or risks associated with diet probably reflect almost exclusively the magnitude of the cumulative biases in this type of research, with extensive residual confounding and selective reporting."

In the meantime, it's probably best to follow your parents' advice with respect to diet and health: Eat and drink in moderation.

Editor's Note: We invite comments and request that they be civil and on-topic. We do not moderate or assume any responsibility for comments, which are owned by the readers who post them. Comments do not represent the views of Reason.com or Reason Foundation. We reserve the right to delete any comment for any reason at any time. Report abuses.

  • loveconstitution1789||

    Apples are oranges now?

    Now we're cooking with grease.

  • Fist of Etiquette||

    As it happens, a 2016 meta-analysis found that "high coffee consumption is associated with a reduced pancreatic cancer risk." Ioannidis is surely right that pervasive nutritional research flip-flops "may have adversely affected the public perception of science."

    But have spawned so many hilarious jokes about whether dark chocolate, eggs and daily doses of wine are good for you this week.

  • I'm Not Sure||

    "requiring that researchers make all of their data available for re-analysis by independent investigators and that results should be presented in their totality"

    Perhaps the global warming folks should be so advised?

  • ||

    your parents' advice with respect to diet and health: Eat and drink in moderation

    HA HA HA HA HA HA!

    Yeah, parents everywhere have been preaching that. As if.

  • lap83||

    More like "finish your plate or the kid in Africa gets it"
    They are like dinner time mobsters

  • lap83||

    Although nowadays it's probably more like "finish your plate or I will guiltily get you whatever you want so you aren't emotionally traumatized"

  • Chipper Morning Baculum||

    [eats all the foreign aid]

  • Aloysious||

    I made pecan pie last night. Does eating and drinking in moderation mean I can't eat the whole thing at once?

  • Brett Bellmore||

    Yes. Yes, it does. Eat it one bite at a time. Otherwise you might choke to death.

  • Chipper Morning Baculum||

    Fuck you. I love pecan pies. And now I want one. Asshole.

  • Aloysious||

    Is there anything better than warm, scratch-made pecan pie? Not sure, but (a slice, Brett. Only a slice.) warm pecan pie with a cup of black coffee for breakfast is right up there.

  • Ron||

    the government is never wrong even when they are wrong, now eat your vegis

  • Chipper Morning Baculum||

  • Longtorso, Johnny||

    The Science is Settled.

  • Oli||

    Nice, it's about time we swing back to the importance of the philosophy of science.

  • Brett Bellmore||

    The basic problem here is that it's fairly easy to establish nutritional requirements for basic health, or establish that something is immediately toxic.

    But once you get beyond that, statistical strength drops, and the weaker the statistical strength, the better you must control confounding variables.

    But, you can't control confounding variables, because people aren't lab rats, you can't control their lives, or even monitor them in detail.

  • ThomasD||

    Both sets of my grandparents lived very long, and relatively healthy lives. I say relatively because they were poor back when being poor meant being skinny, and not having much in the way of routine healthcare.

    They ate soups, lots of soups.

  • Dillinger||

    only safe plan is don't forget to eat.

  • THCorCBDthatistheQuestion||

    Personally I tend to give controlled feeding trials the most weight when looking at nutritional studies, since they're the only studies where the variable of participants lying about their intake is removed.

    I also ignore any studies paid for by the group's selling the studied food products. Aka, don't trust the coconut oil companies to have fair studies on coconut oil, or the egg company to have a fair study on eggs. They'll design the study to make it appear positive to their product, while trying to confuse the media, and other influencers.

    It's really easy to do. Replace a sausage McMuffin and hash brown with eggs for breakfast, and voila! Adding eggs didn't increase cholesterol so they must be healthy. Ignoring the fact that the participants cholesterol stayed the same because you replaced crap with crap.

    And people love hearing good news about their bad habits. (Myself included).

    Basically, eat as little fat and animals as you can, and eat as much whole grain, fruits and vegetables as you can. Easy way to reach a healthy weight.

    I know what you're saying, "But muh baconz!?!?!" Stop eating that unhealthy shit.

    Even Dr. Atkins, the grandaddy of the high-fat diet, says his diet is not meant for long term use because it's bad for you.

  • aelhues||

    Let's take the most obvious, defendable point from that....

    Bacon: What exactly is unhealthy about it, and what proof do you have?

    Which, was the point of the post. We have a lot of evidence, much of it contradictory, and very little in the way of proof.

  • Lewis Goudy||

    " Replace a sausage McMuffin and hash brown with eggs for breakfast, and voila! Adding eggs didn't increase cholesterol so they must be healthy. Ignoring the fact that the participants cholesterol stayed the same because you replaced crap with crap."

    "A few foods, notably egg yolks and some shellfish, are higher in dietary cholesterol but not saturated fats. Eggs and shellfish can be consumed along with a variety of other choices within and across the subgroup recommendations of the protein foods group."
    Dietary Guidelines for Americans, 2015-2020, Eighth Edition)

  • flyfishnevada||

    Nah, bro, it's okay. They just believe the shoddy research that supports their personal diet preferences and disregard the rest. It's cool!

    Seriously, eat whatever you want. We're all going to die of something someday. Besides, have you seen what 90 looks like. It's generally not pretty. Just because you can live to 100 doesn't mean it's a good idea for most people...

  • vek||

    Here's the thing you're missing: In moderation bacon, and any other animal meat/fat is GOOD for you. We evolved to be omnivorous. We don't function correctly on all vegetarian diet, so the key is moderation. Somebody who eats a half pound of bacon a day, a fat steak/pork chop for dinner, and no veggies ever will probably give themselves an early heart attack... But as part of a well rounded diet all that stuff is perfectly fine.

  • I am the 0.000000013%||

    I ate only whole grains and chewed some strange animal jerky hide and went from a 5'8" somewhat barrel shaped white man to a 6'7" marathon winning stereotype with a significantly different tanning profile...

    Not.

    Any nutritional study that isn't coupled with the very latest in genetic analysis is doomed to failure. How you process food is hugely determined by your genetic makeup.

  • vek||

    Some of this stuff is in fact interesting. Genetics is HUGE, and now that we're finally sequencing en masse we're going to have a ton of interesting things pop out. Also, with diet, your lifestyle matters a ton. A guy who does hard physical labor every day might NEED to eat amounts of red meat that would give a desk jockey a heart attack in short order just to keep himself going.

  • I am the 0.000000013%||

    Good points, and I agree about lifestyle - thanks!

  • Malvolio||

    Next you are going to tell me I can't trust supermarket tabloids.

  • newshutz||

    I think this is the winner for most sensible Hihn post in a long time.

  • GoatOnABoat||

    Bacons and egges is good for you! Just ask Edward Bernays. And there's nothing like a Torch of Freedom for an after-meal treat!

  • Uncle Jay||

    Hey, you gotta have nutrition research.
    Otherwise these bureaucrats won't be able to pay off their third vacation home in the Bahamas.

  • WillPaine||

    Mr. Bailey; do you have a point here? Goofy math? You can bet that if you stop eating corpses, your health will improve, no? Junk journalism; nice try?

  • Jay Dubya||

    can you write a sentence that ends without a question mark¿

  • Liberty Lover||

    I don't know a single person that pays any attention to "Government nutrition research". Everyone knows corporations pay money to have the research to find in their favor. Remember eat mostly carbs on the food pyramid? Sure we all want type II diabetes.

  • Brett Bellmore||

    My wife falls for it like a ton of bricks, unfortunately.

  • No Longer Amused||

    Shit, I could have to you all this for free in 1975....

  • vek||

    "In the meantime, it's probably best to follow your parents' advice with respect to diet and health: Eat and drink in moderation."

    Yup, moderation says it all.

    As someone who has casually kept fairly up to date on all this nonsense, with a few spurts of in depth research into stuff, I have come to this conclusion: The very best diet for humans is 70-80% vegetarian, and the vast majority of that should be fruits/veggies, not grains, but some grains are fine. For the rest fatty/high calorie things like red meat, bacon, dairy, eggs, etc are awesome for you and totally fine.

    That is kind of a reasonable consensus from all the stuff that has ever been studied. Keep in mind that is if you want to have a really maximized for health diet. You can switch those percentages around quite a lot, and it won't make a huge difference in health or mortality. What you really don't want to do though is have a diet that is almost all grains, because they're more or less just empty (delicious!) calories, even eating more meat for calories is probably better than grains.

    Just eat a good mix, and don't get overweight, and you'll be fine. I don't eat anywhere close to the ideal, because meat and grains are awesome, but it's good to know what IS closer to ideal too.

  • Jay Dubya||

    dude. the point here is that the consensus view is based on nonsense. the average of a set of bullshit will remain bullshit. there is no objective reason to favor "80% vegetarianism" over steak & potatoes (absent some specific health problem). moderation here means dont eat a ton of steak & potatoes, not a specific dietary recommendation.

  • vek||

    I get your point... But you apparently missed mine. First off I didn't declare anything was a magic silver bullet number. But if you kind of read through a broad swath of everything out there, there are extremes that are known to be garbage. Like eating 100% cotton candy will kill you in short order or whatever.

    Most all research shows people eating modern western diets to be nutrient deficient in lots of things, which IS objective science, not junk science. These nutrients tend to be found in fruits and vegetables. Hence almost everybody ever has said we should eat more of those. A lot of people have come to the conclusion 70-80% of calories should come from plants, with far fewer of those coming from grains since they're mostly empty calories. There's enough of a body of evidence, and I know how to logically think, that this seem reasonable TO ME. Note I did specifically say that was MY conclusion from what I have read.

    Also note "You can switch those percentages around quite a lot, and it won't make a huge difference in health or mortality."

    There's a pretty wide range that is OKAY to be in. You have to get to the extremes before you're really going to hurt your health in short order.

  • vek||

    I DO get your point that we don't 110% KNOW for sure on some of this stuff, but the fruit/veg balance being way out of wack in our modern diet is pretty clear cut for anybody with common sense. Keep in mind I don't follow this rule myself, because I just don't care about being that perfect. But it's probably still the best guess we can make at this point, and likely close to the mark.

    One doesn't have to be 110% positive to make a reasonable guess and roll with where the evidence seems to point, even if it's off a little. That's a bit like ignoring initial studies that showed smoking was bad for people, but deciding to start smoking twice as much, because we're just not 110% sure yet so fuck it!

    The evidence we do have tends to all show a general trend, even if we're not positive on the specifics, it's probably somewhere in the direction of more fruit/veg than most people eat now. It's not an issue where there are studies going both ways on this stuff, even pro meat people still say most people don't eat enough good plant based food in the west. We still don't understand how gravity works for sure, but we know enough to use what info we do have to achieve positive results. You dig?

  • Pat001||

    There's a new study out that says most new studies aren't worth shit.

GET REASON MAGAZINE

Get Reason's print or digital edition before it’s posted online