Many fruits, vegetables, and other foods we’ve long been taught are good for us are quietly making us sick, warns cardiologist Steven Gundry, MD.
Gundry argues that lectins — a group of naturally-occurring proteins found in nearly all plants — are the root cause of most chronic illnesses plaguing modern society.
In his 2017 book The Plant Paradox: The Hidden Dangers in “Healthy” Foods That Cause Disease and Weight Gain, the former heart surgeon lays out a lectin-free lifestyle protocol which he claims can slow the progression of — or even reverse — hard-to-treat conditions like autoimmune disease, obesity, digestive dysfunction, dementia, and heart disease.
A number of patients following Gundry’s Plant Paradox program have experienced dramatic health improvements. But there are significant reasons to question whether his radical recommendations are really appropriate for everyone. Critics also challenge the scientific basis behind Gundry’s broad generalizations, his popular but simplistic sound-byte presentation style, and his overt commercial interests.
Like most diet strategies, the Plant Paradox approach has not been subjected to a blinded clinical trial.
Deflectin’ the Lectins
Do Gundry’s ideas have merit? Yes and no.
To understand what Gundry refers to as the “plant paradox,” one must understand the biochemistry of human and plant interaction.
Plants “are chemists of incredible ability,” he said at the Institute for Functional Medicine’s recent 2018 Annual International Conference in Hollywood, Florida. In addition to producing their own food by turning sunlight into matter — an ability that animals do not possess — they can also “use biological warfare to make you ill.”
Evolutionarily speaking, “plants were here first,” explained Gundry, Founder of the International Heart & Lung Institute, and the Center for Restorative Medicine in California. Prior to the arrival of insects and later, animal predators, plants flourished. When hungry creatures began to walk the land, plants — which cannot run, hide, or fight — developed an array of chemical defense mechanisms to protect themselves from being eaten.
“Most plants actually want to make you ill,” Gundry proposed, describing one botanical safety strategy.
Just like humans and other animals, a plant’s ultimate goal is reproduction, fulfilled by keeping its future babies — in the plant’s case, its seeds — safe from harm. To do this, plants employ the “lectin protection system,” producing toxic substances including lectins in their seeds and other edible parts to defend themselves and their progeny from hungry predators.
Lectins are a broad category of sticky proteins that plants use to “hack their predators’ gut wall, joints, nerves, brain, and immune system,” Gundry said. These proteins, which bind to sugar molecules in the body and cause red blood cells to clump together, are specifically designed to make insects or animals feel sick, fatigued, depressed, hurt, or disoriented.
When “smart” animals eat lectins, they sense danger and leave in search of safer food sources. Humans, on the other hand, tend to ignore the signals plants send to us. Our ignorance, according to Gundry, has serious consequences.
The same plant lectins that kill and immobilize insects, he says, “silently destroy your health and insidiously impact your weight.”
What Not to Eat
Problematically, lectins lurk in a huge number of common foods, from grains and legumes to fruits and nightshade vegetables, even some meats, poultry, and fish. Gundry’s list of “problem” foods is quite long.
What is it about this particular class of proteins that suddenly renders our usual way of eating so dangerous?
Gluten is perhaps the most widely known of the plant lectins. The links between gluten and illness, from Celiac disease to gluten intolerance, are well documented — and yet we pay little, if any, attention to the myriad other lectins we eat regularly.
If we know that gluten does enough damage to trigger autoimmunity and warrant its own line of gluten-free specialty foods, do other lectins also present similar health risks? Gundry believes this is so.
Lectins affect our health primarily by disrupting normal digestion, especially in the small intestine. Not only are they resistant to digestion, they also bind to specific carbohydrates on cell surfaces, triggering changes in normal cellular processes. The FDA notes that “besides inducing mitosis, lectins are known for their ability to agglutinate many mammalian red blood cell types, alter cell membrane transport systems, alter cell permeability to proteins, and generally interfere with cellular metabolism.”
They can also disturb the gut endocrine and immune systems and upset the intestinal microbiome, making us more susceptible to bacterial infections and other health problems. Their effects can manifest in the form of increased intestinal permeability, also known as leaky gut, as well as poor nutrient absorption, diarrhea, weight loss, and growth retardation. Patients with autoimmune or other chronic diseases are especially susceptible to lectins.
Of the thousands of different types of lectins, some are indeed toxic to humans, even in small amounts. Phytohaemagglutinin, a lectin found in legumes like red kidney beans and chickpeas, can cause death. Plants use the deadly compound as a defense mechanism against pests and pathogens. Though the raw beans are fairly toxic, soaking or cooking beans that contain phytohaemagglutinin greatly lowers the toxicity.
“Cooking partially breaks down many lectins,” Gundry said, noting that many cultures have identified methods for detoxifying the dangerous proteins. The traditional Italian preparation of peeling and de-seeding tomatoes before eating them, for instance, removes the lectins from the fruit. Other long-used culinary techniques like soaking, fermenting, and pressure cooking also reduce the lectin content of foods like beans and grains.
To those skeptical of Gundry’s strict diet guidelines, the old toxicology principle “the dose makes the poison” comes quickly to mind. Humans frequently eat natural plant chemicals that, in much larger quantities, would kill us. Apple seeds, almonds, pears, potatoes, summer squashes, and numerous other food crops contain chemicals like cyanide, formaldehyde, and other toxic compounds, but in amounts too small to trigger any destructive effects.
While most scientists conclude that it’s entirely safe to eat fruits and vegetables containing lectins and other low-grade toxins in their naturally low-dose forms, Gundry takes a more extreme stance: He contends that all foods containing lectins should be categorically avoided.
Party Like it’s 9,999 Years Ago
To undo lectin-induced damage, Gundry argues that we need to follow more closely in the footsteps of our ancestors. “Eat the foods that you were designed to eat, and party like it’s 9,999 years ago,” he urged the IFM audience.
This means eliminating all high-lectin food groups from our diet. “What I say not to eat is more important than what I tell you to eat,” he stressed. Gundry recommends avoiding all grains and pseudograins like amaranth, buckwheat, and quinoa, as well as flours made from them. Lentils and other legumes, including beans, peas, peanuts, and all soy products also appear on his “forbidden foods” list.
Then there are the paradoxical “health” foods that, in Gundry’s view, surreptitiously undermine our wellbeing. “Some of the very vegetables and fruits that sustain us simultaneously contain substances that can harm us,” he writes in his book. Those include fruits we mistakenly think of as vegetables, like tomatoes, zucchini, and cucumbers. From a botanical perspective, “anything with a seed is a fruit.” Squashes and members of the nightshade family, including eggplant, peppers, and potatoes, are high in lectins, too.
Sweet fruits are also, for the most part, excluded from the Plant Paradox diet. “Fruit is candy,” Gundry said, explaining that many modern fruit crops — including organic varietals — have been hybridized to boost their sugar content.
Fructose — the main sugar in fruit — is, according to Gundry, a toxin. When we eat it, “70% goes straight to the liver,” where it is detoxified into triglycerides. This presents serious health risks to patients with chronic conditions like cancer.
“Cancer cells much prefer fructose as a fuel source than glucose,” Gundry said. He urged fellow clinicians to “take fruits and seeded veggies away from cancer patients.”
The Plant Paradox program does, however, allow limited consumption of certain fruits, when in season and only in moderation. Long ago, when sugar was an important energy source, fruit consumption was necessary for our survival. To our ancestors, fruit was a precious commodity, only available during certain seasons. Now, supermarkets offer year-round selections of produce grown and shipped in from all over the world, tempting us with an array of foods our predecessors could never have imagined.
So what’s left to eat after taking away grains, legumes, and many fruits and veggies? Cruciferous vegetables, leafy greens, and other vegetables without seeds are the mainstays of the Plant Paradox diet. It can also include certain starchy vegetables, particularly those high in resistant starch. Many oils, tree nuts, and seeds appear on the “approved foods” list, as do wild-caught fish, grass-fed meat, and pasture-raised poultry. Gundry also okays the consumption of goat and sheep milk and cheeses, and other select dairy products.
Holes in the Theory
Some lectins are, without a doubt, unhealthy for some patients.
But in going entirely lectin-free, those who strictly adhere to the Plant Paradox program also lose a host of beneficial phytonutrients that exist alongside lectins in the vegetables and fruits they no longer consume. For the right patient, removing high-lectin foods may improve health. For others, however, eliminating all lectins might also mean eliminating crucial nutrients.
In his writings and lectures, Gundry makes a fairly convincing and often entertaining case to support his Plant Paradox prescriptions. But his critics need not work too hard to poke holes in his sweeping generalizations.
As Michael Greger, MD, points out in a video posted on www.nutritionfacts.org, many of the lectin-rich foods vilified by Gundry–beans, whole grains, and seed-containing vegetables–are cornerstones of the diets of people living in “Blue Zone” countries known for their extreme longevity and robust health. Greger, a lifestyle-focused vegan physician who is himself the author of a popular diet book (How Not to Die), reviews numerous studies and metanalyses showing that increased consumption of “lectin-lush” legumes and whole grains correlates with reduced risk of CVD, obesity, diabetes, cancer, and all-cause mortality.
If lectin-rich vegetables and fruits are such illness-inducing nightmares, why–Greger asks–aren’t people in Crete, Sardinia, Loma Linda California, and other Blue Zones suffering and dying from the diseases Gundry attributes to high lectin consumption?
Greger accuses Gundry of playing loose and fast with science. He also reveals that Gundry sells a line of “Lectin Shield” supplements–for $79.95 per month–that purport to “assist your body in the fight against lectins” and “promotes regularity and pleasant bathroom visits.”
Gut Bacteria — Not Genes — Define Us
Gundry brings a significant degree of clinical credibility as well as personal experience to his argument. A renowned cardiac surgeon, Gundry was a pioneer in the development of heart transplantation surgery, left ventricular assist devices (LVADs), robot-assisted minimally invasive heart procedures. He also suffered from overweight, high blood pressure, migraines, arthritis, high cholesterol, and insulin resistance.
A quest to improve his own health led his research on ancestral eating patterns and the healing power of clean eating, which informed the dietary advice he began offering his patients. The improvements he saw in himself and in his patients led him to the conclusion he could no longer continue to “operate first, counsel later.”
Foods that support a healthy microbiome are the core of Gundry’s dietary recommendations. He argues that the divergence between human and non-human primates’ microbiomes marked a critical turning point in our collective health history. While a small portion of our genetic code is uniquely human, we share 99% of our DNA with chimpanzees and gorillas. “We have virtually the same genes as them,” Gundry stated, but “what makes us different is the bacteria and viruses that live in us.”
When humans evolved from great apes, we began spending more time on the ground and less in the trees, and our microbiomes evolved accordingly.
“We can identify that point in time that bacteria made us, rather than our genes,” Gundry proposed. “Bacteria states and variations, especially in the gut, determine who we are.”
Certain bacteria, we now know, can influence food-related behaviors; they can affect the kinds of foods we seek out, as well as our appetites and perceptions of hunger or satiety.
Gundry discussed the health dangers associated with saturated fats, for example, noting that “obesogenic” gut bacteria thrive on them. Studies associate high saturated fat consumption with decreased microbiome diversity as well as obesity, metabolic syndrome, and gastrointestinal disease.
Instead of eating or cooking with refined oils, Gundry recommends healthier choices like olive oil. In fact, he recommends consuming an entire liter of olive oil every week. A man given to amusing exaggerations, he boldly told the IFM crowd that, “The only purpose of food is to get olive oil into your mouth.”
Cataclysmic Culinary Changes
Gundry is among a wave of prominent physicians, researchers and authors who look to “ancestral” eating patterns for possible solutions to today’s health challenges. His Plant Paradox recommendations are, in a sense, a variant of the “paleo” diets that have become popular in recent years. But what is “ancestral” for one person is not necessarily ancestral for another, given the diversity of our ethnic and geographical origins. Further, the realities of “indigenous” eating patterns can be quite different from the modern supermarket versions promoted by paleo enthusiasts, a fact well documented in the National Geographic article, “The Evolution of Diet” several years ago
That said, what nearly all ancient eating patterns have in common is an absence of refined sugars, large quantities of fat, and highly processed foods, and a prevalence of raw or minimally cooked vegetation and wild-caught animal protein. Gundry points to several “cataclysmic” dietary changes over the last 10,000 years–a blink in the evolutionary timescale– that set the stage for today’s rising chronic disease rates.
The Rise of Agriculture: First was the agricultural revolution. Around 10,000 years ago, human eating patterns began to shift dramatically when we started growing our own food. Grains and beans were among the earliest cultivated crops, and they quickly became new dietary staples in many cultures across the globe.
The problem with grains and beans, Gundry posits, is the way they interact with the microbiome. Prior to agriculture, human gut microbes were well-adapted to handle our intake of leaves, tubers, and animal fats and proteins. Incorporating the then-new foods meant our microbiomes had to adjust to the lectins in grasses or legumes that they’d never encountered before. Though developments like crop cultivation and storage granaries enabled unprecedented population and civilization growth, they also helped boost our lectin consumption to levels much greater than we’d consumed as hunter-gatherers.
Cattle Breeding: The second problematic historical event Gundry highlights is a genetic mutation that occurred in cows around 2,000 years ago. Northern European cows suffered a spontaneous mutation that caused them to start producing the lectin-like protein casein A-1 in their milk instead of the “normal” casein A-2. Casein A-1 turns into the protein beta-casomorphin during digestion and attaches to insulin-producing beta cells in the pancreas. This prompts an immune attack on the pancreas in some people who consume milk or other dairy products made from casein A-1-producing cows. Gundry identifies this as a likely cause of diabetes, stating that people who drink milk containing casein A-1 show higher incidence of diabetes than those drinking casein A-2 milk.
There’s some evidence that casein A-1 is a risk factor in other diseases, too. It causes symptoms of what might be misdiagnosed as lactose intolerance, which, Gundry, argues, disappears when patients consume dairy derived from casein A-2-producing cows. The most common cow breed in the world is the hardy Holstein, whose milk contains casein A-1. But cows, goats, and sheep in southern Europe continue to produce casein A-2 milk. Gundry described patients who thought they had lactose intolerance, but then found when traveling in countries like Italy that they could eat traditional dairy products like gelato with no ill effects.
Unlike many variants of “Paleo” and other low-carb or ketogenic diets, which tend to encourage high consumption of animal proteins and fats, Gundry’s diet mostly centers around approved plant foods. It does, however, incorporate limited amounts of “safe” casein A-2 dairy and small servings of pastured meats, wild fish, and shellfish. Egg yolks — though not egg whites–are on Gundry’s approved list. Some tree nuts are allowed as well. Vegan and vegetarian versions of the Plant Paradox diet exist for those who wish to omit animal products altogether.
New World Plants: Another major change in lectin exposure occurred five centuries ago, Gundry says, when European explorers reached the Americas. The conquistadors brought New World crops back to Europe, introducing the “Old World” to an array of lectin-rich foods. Trade helped facilitate the spread of certain nightshades, beans, grains, peanuts, cashews, squashes, chia and other seeds, into new regions.
“Until then, no European, Asian, or African had ever seen, much less eaten” these crops, Gundry writes. “Half of the foods you have been told to eat for good health are actually New World plants that most of mankind had no prior exposure to, meaning your body, your gut bateria, and your immune system are ill-prepared to tolerate them,” he says.
According to Gundry’s book, “getting to know a new lectin in five hundred years is equivalent to speed dating in evolution.”
While his point here may sound sensible to those of European ancestry, it also indicates Gundry’s strong Euro-centric bias. Humans indigenous to the New World were surely eating New World crops long before established trade routes carried them to Europe and elsewhere — but the Plant Paradox approach seems to subtly suggest that New World plants somehow mastered chemical warfare, while “old world” crops are somehow inherently safer. In reality, some ancient Old World crops are also known to cause health problems in some people. Eggplant, for instance, likely originated in Asia, and triggers an allergic reaction to a small percentage of people.
The Chemical Revolution: Those skeptical of Gundry’s restrictive diet might wonder why, if we’ve been eating things like tomatoes, beans, and wheat the past several hundred years, are they suddenly so problematic. Critics argue that the human body is remarkably adaptable and should, theoretically, have adjusted over time to changing environmental conditions.
What’s different now, Gundry says, is that contemporary humans face an unprecedented array of new toxins that our ancestors never had to worry about. He calls these modern assaults the “seven deadly disruptors,” and they include things like endocrine disrupting chemicals in plastics, herbicides and pesticides like glyphosate, food additives and colorings, artificial sweeteners, industrial chemicals, blue light, genetically modified organisms, and a host of pharmaceuticals like broad spectrum antibiotics, NSAIDs, and acid blockers.
Whether or not the Plant Paradox diet is right–or even feasible–for everyone, Gundry’s general lifestyle guidelines will certainly eliminate a host of detrimental foods, and provide a solid foundation for good health for any individual who can actually stick with the program.