How can we distinguish between a sufficiently objective science communicator and an advocate? Communicating science to the public means choosing scientific papers, reading them, and appraising their worth before synthesizing all of this knowledge. We try to do it as impartially as we can… but what if we are ideologically biased?
Dr. Michael Greger is a well-known physician and communicator online. Since 2011, he has been the founder (and now Chief Science Officer) of NutritionFacts.org, which he calls a non-commercial public service meant to educate people on nutrition. It’s a slick, multimedia empire: over a dozen employees and volunteers managing near-daily video uploads, as well as articles and podcast episodes (although the same content ends up feeding all of these platforms). Outside of the Internet, Greger also gives talks. In early March, he will be part of theĚý, a cruise that will take wellness hopefuls from Galveston, Texas, to Mexico and Honduras and back.
Greger’s videos—where he discusses scientific studies in voiceover—are clear, well-produced, and short. So, what’s the problem?
Greger is a vegan, which in itself is not troublesome. But it seems to motivate him to say things that are not borne out by the data.
To err on the side of nature
I took a scattershot approach to Greger’s work, sampling multiple videos, articles, and podcast episodes, as well as looking at the work of some of his critics. To call him a quack would be incorrect. He has good things to say aboutĚý, and he denounces many alternative approaches that promise toĚý. So far, so good.
Sometimes, he and his staff get something wrong because, I suspect, they’re going too fast and they miss important work. In aĚýĚýand in aĚýĚýon vaccines, both published in 2024, he laments the problem that debunking vaccine mythsĚýwillĚýmake people less likely to vaccinate—a phenomenon known as the backfire effect. I’m familiar with this effect, because it was scary when first described. ButĚýĚý—including aĚýĚýby one of the authors of the original backfire effect paper—showed that it had been grossly exaggerated and may only occur in rare circumstances. The famousĚý, to which one of the backfire effect authors contributed, actually advocatesĚýforĚýdebunking. ItĚýcanĚýwork in vaccine conversations, and Greger should know this.
Other mistakes slip in because of chemophobia. Our universe is made up of chemicals, but many people have this irrational fear of things they perceive as artificial and toxic. Given Greger’s preaching for a plant-based diet, I’m not surprised that he views so-called chemicals through a suspicious, if not alarmist lens. HisĚýĚýis predictable: he is wary of the chemical ones and instead recommends the mineral ones (which contain titanium dioxide or zinc oxide, for example). The Food and Drug Administration labels these two minerals “generally recognized as safe” or GRAS, but there is no such designation for the active ingredients in chemical sunscreens, a fact Greger calls a “bombshell.”
It’s not, and we too can play this game. U.S. Right to Know, a nonprofit funded by the organic food lobby, has argued that the mineralĚýĚýand that it has been banned in Europe as a food additive. Is that a bombshell? Nothing is 100% safe in large enough amounts, not even water.
What concerns Greger is recent data showing that the active ingredients in chemical sunscreensĚý, meaning that some small amount doesn’t stay on the skin. This is not proof they are unsafe: in fact, no harm has been proven, and oxybenzone, a common ingredient in chemical sunscreens, has been used in U.S. sunscreens since 1978. U.S. regulation now wants to take absorption through the skin into account, which is good, butĚý. The limits they have set are very similar to the current American limits. It all sounds like a tempest in a teapot, and not a bombshell as Greger described it.
If synthetic compounds bring out his suspicion, natural ones invite his generosity. A few threads of saffron every day, he tells us, improves visual acuity in people with age-related macular degeneration, and rubbing the expensive spice as part of a gel on a man’s genitalia ameliorates its, uh, function, according toĚý. Saffron for the win, right?
The four studies on macular degeneration are not very impressive. Of the two conducted in Italy, theĚýĚýconcludes that “clinical significance is yet to be evaluated” and theĚýĚýhad no control group and the participants knew they were taking saffron. The otherĚýĚýĚýwere done in Iran, the world’s biggest producer of saffron, and as I’ve writtenĚýbefore, nationalistic pride must be kept in mind as an influence here, much like with acupuncture studies done in China. The Iranian study results are a mixed bag, with improvement seen halfway through the trial but not at the end of it. None of this is convincing, and Greger should know better. As for saffron’s aphrodisiac effects, it comes from aĚýĚýconducted in—surprise, surprise—Iran, and while the results areĚýstatisticallyĚýsignificant, the differences between the control group and the saffron group are very small. This is weak sauce.
The thing is, “Nutrition Facts” sounds even-keeled. But Greger’s nonprofit, according to theĚý, used to go by another name: Vegan Research Institute Inc.
A diet of whole and holy plants
If you want both you and the planet to be healthy, you could do a lot worse than to adopt a plant-based diet, whether it’s vegetarian (which can allow for dairy, eggs, and honey) or strictly vegan. Meat production has aĚýĚýon our planet. It also incurs a moral cost—the raising and killing of conscious animals—which us meat eaters must either wrestle with or conveniently ignore.
Dietitians of Canada developed a paid tool calledĚý, which the organization manages in partnership with Dietitians Australia and the British Dietetic Association. As summarized on PEN and based on the best evidence we have, vegetarian diets may be associated with a lower overall risk of developing cancer, especially colorectal cancer (and this goes for diets that still allow fish or are semi-vegetarian). Vegetarians have a lower risk of getting type 2 diabetes, and their diet may be effective at preventing cardiovascular disease in someone who has never had it when compared to a non-vegetarian diet or to no intervention at all, but not necessarily better than other healthy diets.
The Academy of Nutrition and Dietetics in the U.S. likewise stated inĚýĚýthat vegetarian diets may prevent and treat a long list of diseases, while keeping in mind that they can incur deficiencies (like vitamin B12) that need to be controlled for or supplemented. Many governmental health agencies stop just short of strongly recommending a plant-based diet to everyone simply because it’s a radical departure for many and nudging the population toward healthier eating in general is likely to be more productive.
But when Dr. Michael Greger compares vegetarianism with meat-eating, he might as well be pitting heaven against hell. In a 2012 video entitledĚýĚýGreger tells his viewers that meat contaminated with “fecal food-poisoning bacteria” can still legally be sold, quoting a USDA poultry microbiologist who draws an analogy between raw meat and hand grenades. Greger’s precious plants, however, shouldn’t escape from these accusations: nearlyĚýĚýin his country are due to produce. A head of lettuce can also be a hand grenade, yet plants are never mentioned in the video.
In 2019, Greger published a book calledĚýHow Not to Diet: The Groundbreaking Science of Healthy, Permanent Weight Loss. It was an instantĚýNew York TimesĚýbest-seller. Five years later, the websiteĚýĚýtook a gander at Greger’s book, which encourages a diet of minimally processed plants, and gave its scientific accuracy a disappointing 50% score. What did its team of expert scientists do? To borrow Greger’s catchphrase, they put his book to the test.
They reviewed the first three claims Greger makes in his book: two of them either lacked evidence or the evidence was unconvincing. He also later claimed that a plant-based diet canĚýreverseĚýheart disease while citing, as proof, a study that only looked atĚýpreventingĚýheart disease in the first place. And he writes that, since nicotine can help with weight loss, eating nightshade vegetables like tomatoes and peppers—which contain nicotine—will give you the weight-loss benefit without the harms from smoking. The only caveat is that you would need to eat hundreds if not thousands of pounds of these vegetables to get the same amount of nicotine you find in a single cigarette. It’s the dose that makes the poison, yes, but the dose also makes the cure.
Greger exaggerates. He puts plants up on a pedestal, which allows him and his team to cut corners. They distort studies, weaponize them, and take preliminary findings in tiny cohorts to mean that your spice cabinet is an untapped pharmacy. As Red Pen Reviews concludes, the diet Greger advocates for comes with an array of dietary recommendations that “seem unnecessary, too restrictive, or potentially counterproductive.” To lose weight, Greger advocates for “anti-inflammatory” ingredients high in fibre and water and low in added fat, added sugar, and so-called addictive potential, with meals that avoid oils and are low in meat, eggs, dairy, refined grains, salt, glycemic load, and insulin index, while rich in fruits, vegetables, and legumes. Not impossible to achieve, for sure, but not easy for most to maintain.
Never trust a single source
I don’t believe Greger is a grifter in the traditional sense of deceiving for the purpose of enriching his bank account. Everywhere you look is a disclaimer stating that all proceeds from book and DVD sales, as well as his speaking fees, areĚý. One half goes to his nonprofit, NutritionFacts.org, while the other half is said to be handed out to a donor-advised charitable fund that gives the money to nonprofits engaged in nutritional policy, like Balanced and the Physicians Association for Nutrition. Greger takes no corporate sponsorships, he claims, nor does he sell any dietary supplements—a refreshing change from the usual nature worshipper. Seed money for his project came from the Jesse and Julie Rasch Foundation, and according toĚýĚýfor the year 2022, Greger was compensated USD 199,403 by his nonprofit, which itself declared nearly 2.3 million dollars in total revenues.
Bias is a real problem in our information landscape. Doctors, scientists, and journalists don’t escape it—and neither does Greger. We try our best to recognize it in ourselves and to seek out evidence that disagrees with us. We endeavour to question the studies that agree with usĚýas muchĚýas the ones that disagree with us, to find flaws in them and to contextualize them. Many do it better than Greger and his team, I would argue.
He has a new book out, of course. It’s calledĚý. The minimal cover shows a plate of orange chunks of processed food, like a Cheeto and a piece of textured vegetable protein had a baby. One of them, the one in the middle, is shaped like a skull.
Judging the book by its cover—and its author’s track record—do you expect nuance from it? Or advocacy?
Take-home message:
- Dr. Michael Greger, who advocates for a plant-based diet, answers questions that pertain to nutrition through his nonprofit, NutritionFacts.org.
- While some of the information he puts forward is backed up by good scientific evidence, he regularly demonizes synthetic compounds, exaggerates the danger posed by eating or handling meat, and is uncritical of inadequate studies alleging all sorts of benefits for plant-based compounds.
