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鈥� 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鈥檚 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 the听, a cruise that will take wellness hopefuls from Galveston, Texas, to Mexico and Honduras and back.
Greger鈥檚 videos鈥攚here he discusses scientific studies in voiceover鈥攁re clear, well-produced, and short. So, what鈥檚 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鈥檚 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 about听, and he denounces many alternative approaches that promise to听. So far, so good.
Sometimes, he and his staff get something wrong because, I suspect, they鈥檙e going too fast and they miss important work. In a听听and in a听听on vaccines, both published in 2024, he laments the problem that debunking vaccine myths听will听make people less likely to vaccinate鈥攁 phenomenon known as the backfire effect. I鈥檓 familiar with this effect, because it was scary when first described. But听听鈥攊ncluding a听听by one of the authors of the original backfire effect paper鈥攕howed that it had been grossly exaggerated and may only occur in rare circumstances. The famous听, to which one of the backfire effect authors contributed, actually advocates听for听debunking. It听can听work 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鈥檚 preaching for a plant-based diet, I鈥檓 not surprised that he views so-called chemicals through a suspicious, if not alarmist lens. His听听is 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 鈥済enerally recognized as safe鈥� or GRAS, but there is no such designation for the active ingredients in chemical sunscreens, a fact Greger calls a 鈥渂ombshell.鈥�
It鈥檚 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 mineral听听and 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 sunscreens听, meaning that some small amount doesn鈥檛 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, but听. 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鈥檚 genitalia ameliorates its, uh, function, according to听. Saffron for the win, right?
The four studies on macular degeneration are not very impressive. Of the two conducted in Italy, the听听concludes that 鈥渃linical significance is yet to be evaluated鈥� and the听听had no control group and the participants knew they were taking saffron. The other听听听were done in Iran, the world鈥檚 biggest producer of saffron, and as I鈥檝e written听before, 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鈥檚 aphrodisiac effects, it comes from a听听conducted in鈥攕urprise, surprise鈥擨ran, and while the results are听statistically听significant, the differences between the control group and the saffron group are very small. This is weak sauce.
The thing is, 鈥淣utrition Facts鈥� sounds even-keeled. But Greger鈥檚 nonprofit, according to the听, 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鈥檚 vegetarian (which can allow for dairy, eggs, and honey) or strictly vegan. Meat production has a听听on our planet. It also incurs a moral cost鈥攖he raising and killing of conscious animals鈥攚hich us meat eaters must either wrestle with or conveniently ignore.
Dietitians of Canada developed a paid tool called听, 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 in听听that 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鈥檚 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 entitled听听Greger tells his viewers that meat contaminated with 鈥渇ecal food-poisoning bacteria鈥� can still legally be sold, quoting a USDA poultry microbiologist who draws an analogy between raw meat and hand grenades. Greger鈥檚 precious plants, however, shouldn鈥檛 escape from these accusations: nearly听听in 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 called听How Not to Diet: The Groundbreaking Science of Healthy, Permanent Weight Loss. It was an instant听New York Times听best-seller. Five years later, the website听听took a gander at Greger鈥檚 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鈥檚 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 can听reverse听heart disease while citing, as proof, a study that only looked at听preventing听heart disease in the first place. And he writes that, since nicotine can help with weight loss, eating nightshade vegetables like tomatoes and peppers鈥攚hich contain nicotine鈥攚ill 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鈥檚 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 鈥渟eem unnecessary, too restrictive, or potentially counterproductive.鈥� To lose weight, Greger advocates for 鈥渁nti-inflammatory鈥� 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鈥檛 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, are听. 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鈥攁 refreshing change from the usual nature worshipper. Seed money for his project came from the Jesse and Julie Rasch Foundation, and according to听听for 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鈥檛 escape it鈥攁nd 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 us听as much听as 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鈥檚 called听. 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鈥攁nd its author鈥檚 track record鈥攄o 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.
