The Plant Paradox: Steven Gundry’s War on Lectins

Most of what Steven Gundry says in his book The Plant Paradox is demonstrably wrong. There is no science-based reason to avoid lectins.

A correspondent asked me to review a book by Steven Gundry, The Plant Paradox: The Hidden Dangers in “Healthy” Foods That Cause Disease and Weight Gain. I intended to reserve judgment and just look into which claims were supported by credible science, but I was put off by the very first sentence:

…everything you thought you knew about your diet, your health, and your weight is wrong.

Isn’t he essentially asking us to reject science? Some of the things we know have been proven by good science, with multiple approaches and multiple systematic reviews of controlled studies that are in agreement. And of course, he is going to cite scientific studies to support his own claims. Who gets to be the arbiter of what is good science and what the rest of the world got wrong? Gundry himself, of course. He says “with all modesty” (Hah!) he has found there is a common cause for most health problems that the rest of the medical establishment doesn’t know. Only he does. He can reverse heart disease and cure whatever is wrong with you through diet alone. (Yeah, sure!)

In the introduction “It’s Not Your Fault” he brags about his expertise as a cardiologist and researcher but he inadvertently reveals how he came to the wrong conclusion about diet. He had been eating what he was told was a healthy diet and was exercising as recommended, but he was overweight, had high blood pressure, migraine headaches, arthritis, high cholesterol, and insulin resistance. All these problems resolved when he changed his diet. He lost 70 pounds. Couldn’t the weight loss, instead of his new diet, account for the improvements?

His program starts with a 3-day cleanse (“cleanse” is a pseudoscience buzzword!) and promises to banish most of your health problems, achieve a healthy weight, reboot your energy level, and elevate your mood. Such a deal! But can we believe it? Let’s look at the science behind the claims.

Plants produce chemicals to defend themselves from predators and you are a predator. The plant paradox, according to Gundry, is that while they offer essential health benefits they are also trying to kill you.

He says lectins cause inflammation, stimulate weight gain, and cause leaky gut syndrome. With the agricultural revolution, grain and beans quickly became the dietary staples of most cultures. These were toxic, but Gundry says when humans were faced with a choice between starvation and surviving with serious health trade-offs, they opted for survival.

Gundry explains that milk from different breeds of cow may contain either casein A-1 (Ayrshire, British Shorthorn, Holstein, and Friesian) or casein A-2 (Charolais, Guernsey, Jersey, and Limousin). (This is not strictly accurate. Actually, the breeds in his A-1 list produce equal amounts of A-1 and A-2.) His diet strictly prohibits milk and dairy products from casein A-1 cows; it only allows casein A-2 milk and alternative dairy products. On his website he calls casein A-1 “incredibly noxious”. He believes it is the primary cause of type 1 diabetes.

What does science say? It says there is some intriguing evidence, but causation of diabetes by A-1 remains unproven. And science says there is a lack of definitive human trials to support the various health claims for the superiority of casein A-2 milk. The first systematic review was published in 2017. It found only three human studies, one study showing delayed intestinal transit for casein A-1 milk and two studies that showed looser stool consistency. So what? The studies didn’t show that these changes harmed people. These were secondary markers; none of those studies looked at clinical outcomes, at so-called POEMS (patient-oriented evidence that matters). The rest of the published evidence was all from animal studies.

He claims lectin avoidance, “as reported in the scientific literature” has been found to cure autoimmune diseases. The reference he gives from the scientific literature is “Curing/remission of multiple autoimmune diseases is possible by manipulation of the human gut microbiome” in the Journal of International Society of Microbiota. He lists himself as the author. I had difficulty locating it and finally discovered it was not a published, peer-reviewed article but an abstract only available to members. An article with the same title was listed as a poster/abstract presentation in the journal Circulation. It was not listed on PubMed. In fact, I could not find a single article by SR Gundry anywhere in PubMed. I was amazed and shocked to find nothing in PubMed for someone who calls himself a researcher.

In the book he describes many case reports of patients who improved on a lectin-limited diet, but he has done no studies with a control group for comparison, so his “evidence” is anecdotal and meaningless. And he has no business extrapolating from inadequate evidence and animal studies to give general advice about what all humans should and shouldn’t eat. He is clearly not a reliable source of medical information and is not to be trusted. He claims, without evidence, that “Everyone who has a disease has a leaky gut”. Leaky gut is not a recognized medical diagnosis; many doctors deny that it exists. And he sells his own line of supplements. And his book is also a cookbook featuring many recipes, some of which sound very unappetizing.

I was appalled that an MD could be so inept at providing references and so clueless about what constitutes evidence and about basic principles of science like the need for a control group.

What are lectins?

Lectins are carbohydrate-binding proteins that are found in most foods. They can be harmful. Kidney beans are toxic but only if eaten raw, which no one does; proper cooking neutralizes the lectins and makes kidney beans safe to eat. Not only safe, but beneficial. Lectins play essential roles in human physiology. Among their many important functions, they regulate cell adhesion and are the first-line defense against invading microorganisms in the innate immune system.

Steven Gundry’s diet

The Plant Paradox diet excludes whole grains, legumes, most fruit, certain nuts and seeds, A-1 dairy products, and the nightshade vegetables (tomatoes, potatoes, eggplant, bell peppers, and chili peppers). A full list of foods to avoid and foods that are OK is available on Gundry’s website. It is extensive. It’s easy to see that following such a restricted diet is likely to reduce total calorie intake and result in weight loss. Substantial weight loss as well as placebo responses may explain why so many of Gundy’s patients believe his no-lectin diet has helped them.


A large number of doctors, nutritionists, and scientists have criticized The Plant Paradox. Some of them are listed on the Wikipedia article, including T. Colin Campbell, the author of The China Syndrome, which I reviewed here. I thought the best of all the critical articles was a long, detailed, and well-reasoned article by Michael Matthews. He debunks Gundry’s thesis, giving “7 science-based reasons it’s a scam”:

The Plant Paradox is rife with inaccuracies, misrepresentations, and outright misinformation, and the diet espoused in it is unnecessarily restrictive and blatantly designed to sell people overpriced and ineffective supplements…there’s enough high-quality research to say we know enough about lectins to blow all of Dr. Gundry’s principal hypotheses out of the airlock and thereby dismantle and disarm The Plant Paradox.

Michael Matthews is a personal trainer, not a physician or scientist, and he also is guilty of selling unproven dietary supplements, so I will be criticized for citing him, but of the many critiques of Gundry’s book I found on the Internet, I thought his was by far the best, the most detailed and well-reasoned. It is based on good science and supported by links to published evidence. He reviews the supplements Gundry sells that Gundry says are essential.

The bottom line is Dr. Gundry’s products are a sham, what with the fake science, unproven ingredients, and miniscule dosages.

He doesn’t mince words and his language is not afraid to resort to insults. He calls Gundry “a once-prestigious heart surgeon turned diet quack”. Actually, I think that’s true.

He responds to all the comments following his article and does an excellent job of answering the complaints of true believers with tact and accurate information, and with no insulting language. He tells them he is glad they are feeling better, without reaffirming their belief that lectin avoidance is the cause of their improvement. I was impressed.

His article “Dr. Gundry’s Plant Paradox Debunked: 7 Science-Based Reasons It’s a Scam” can be found on the LegionAthletics website. It repeats what he says in his podcast on Gundry.

Conclusion: Gundry is wrong

The book The Plant Paradox is not science-based medicine. It is…something else. I won’t try to say what it is because I would be tempted to resort to profanity. Lectins are not our enemies, and the foods Gundry prohibits are part of a science-based healthy diet. Avoiding them might lead to inadequate nutrition.

This article was originally published in the Science-Based Medicine Blog.

Dr. Hall is a contributing editor to both Skeptic magazine and the Skeptical Inquirer. She is a weekly contributor to the Science-Based Medicine Blog and is one of its editors. She has also contributed to Quackwatch and to a number of other respected journals and publications. She is the author of Women Aren’t Supposed to Fly: The Memoirs of a Female Flight Surgeon and co-author of the textbook, Consumer Health: A Guide to Intelligent Decisions.

Scroll to top