What Steven Gundry's Book 'The Plant Paradox' Adds to the Principles of a Low-Insulin-Index Diet

I have been reading a remarkable book: The Plant Paradox by Steven Gundry. I find the book persuasive, both due to its logical arguments and because of my experience in experimenting myself with its recommendations. Starting from a low-insulin-index diet (see “Forget Calorie Counting; It's the Insulin Index, Stupid”) that tries to avoid too much animal protein (see “Meat Is Amazingly Nutritious—But Is It Amazingly Nutritious for Cancer Cells, Too?”), the changes needed to follow Steven Gundry’s recommendations weren’t huge, but in my assessment have made me feel better than ever. In particular, I have noticed feeling especially clearheaded, and I have felt an almost indestructible cheerfulness in the last couple of months while following those recommendations, despite being in the stressful situation of writing two grant proposals at once.

In this post, I’ll focus on Steven’s logical arguments and the most basic practical implications of those arguments. For the most part I’ll leave writing in detail about how I have reoptimized my diet to later posts. But there is one post in which I already did an update based on The Plant Paradox: “Our Delusions about 'Healthy' Snacks—Nuts to That!" There, I added this, which can serve as an executive summary for today’s post:

I am currently reading Steven Gundry's book The Plant Paradox. So far, I am impressed. He argues that peanuts and cashews (technically legumes and drupes respectively, not nuts) are unhealthy because they contain a lot of lectins (natural insecticides that plants produce) that humans are ill-adapted to detoxify because they were plants from the Americas. Even those of Native American descent have had at most about 14,000 years for evolution to develop defenses against these particular lectins. For the rest of us, it is only 526 years since Columbus. And it is a lot more complex to evolve defenses against particular lectins than, say, the extension of the ability to digest milk into adulthood.

I was never a big fan of peanuts, so avoiding them is no change for me, but currently I have cut out cashews. Also, based on Steven Gundry's advice, I am currently switching to blanched (deskinned) Marcona almonds and shifting away from almond milk toward coconut milk. (I was annoyed to find that Costco's Marcona almonds are roasted in peanut oil, which means I have to get my Marcona almonds online.) 

The War Between Plants and Animals

The first key point in Steven’s argument is that plants have evolved natural insecticides—many of them in the class of chemicals called lectins. These natural insecticides are not healthy for humans, but some are worse than others. The immediately following quotations are from Chapter 1: “The War Between Plants and Animals.”

… plants don’t want to be eaten—and who can blame them? Like any living thing, their instinct is to propagate the next generation of their species. To this end, plants have come up with devilishly clever ways to protect themselves and their offspring from predators. …

… Plants have actually evolved an awesome array of defensive strategies to protect themselves, or at least their seeds, from animals of all shapes and sizes, including humans. Plants may use a variety of physical deterrents, such as color to blend into their surroundings; an unpleasant texture; sticky stuff such as resins and saps that entangle insects, provide protective cover by making sand or soil clump, or attract grit that makes them unpleasant to eat; or a simple reliance on a hard outer coating, such as a coconut, or spine-tipped leaves, such as an artichoke. Other defensive strategies are far subtler. Plants are great chemists—and alchemists, for that matter: they can turn sunbeams into matter! They have evolved to use biological warfare to repel predators—poisoning, paralyzing, or disorienting them—or to reduce their own digestibility to stay alive and protect their seeds, enhancing the chances that their species will endure. Both these physical and chemical defensive strategies are remarkably effective at keeping predators at bay, and even sometimes at getting animals to do their bidding. Because their initial predators were insects, plants developed some lectins that would paralyze any unfortunate bug that tried to dine on them. Obviously, there is a quantum size difference between insects and mammals, but both are subject to the same effects. (If you are suffering from neuropathy, take notice!) Clearly, most of you won’t be paralyzed by a plant compound within minutes of eating it, although a single peanut (a lectin) certainly has the potential to kill certain people. But we are not immune to the long-term effects of eating certain plant compounds. Because of the huge number of cells we mammals have, we may not see the damaging results of consuming such compounds for years. And even if this is happening to you, you don’t know it yet. I learned of this connection via hundreds of my patients who respond almost instantly, often in fascinating ways, to these mischievous plant compounds. For this reason, I call these patients my “canaries.” Coal miners used to take caged canaries into the mines with them because the birds are especially subject to the lethal effects of carbon monoxide and methane. As long as the canaries sang, the miners felt safe, but if the chirping stopped, it was a clear signal to evacuate the mine posthaste. My “canaries” are more sensitive to certain lectins than the average person, which is actually an advantage in terms of seeking help sooner rather than later.

Here is some of the biochemistry of why lectins are bad:

[Lectins] also bind to sialic acid, a sugar molecule found in the gut, in the brain, between nerve endings, in joints, and in all bodily fluids, including the blood vessel lining of all creatures. Lectins are sometimes referred to as “sticky proteins” because of this binding process, which means they can interrupt messaging between cells or otherwise cause toxic or inflammatory reactions, as we’ll discuss later. For example, when lectins bind to sialic acid, one nerve is unable to communicate its information to another nerve. If you have ever experienced brain fog, thank lectins.

Grains have both lectins and other unpleasant chemicals:

IN THE CASE of naked seeds, plants use a divergent strategy. … Instead of a hard casing, the naked seed contains one or more chemicals that weaken predators, paralyze them, or make them ill, so they won’t make the mistake of eating the plant again. These substances include phytates, often referred to as antinutrients, which prevent absorption of minerals in the diet; trypsin inhibitors, which keep digestive enzymes from doing their job, interfering with the predator’s growth; and lectins, which are designed to disrupt cellular communication by, among other things, causing gaps in the intestinal wall barrier, a condition known as leaky gut. Whole grains actually contain all three of these defensive chemicals in the fibrous hull, husk, and bran. (Teaser alert: This is just one reason that the idea of “whole-grain goodness” is a huge misconception, as you’ll learn in chapter 2.)

Nightshades such as tomatoes and potatoes also have tannins:

Still other plant-predator dissuaders include tannins, which impart a bitter taste, and the alkaloids found in the stems and leaves of the nightshade family. You may already know that nightshades, which include such culinary favorites as tomatoes, potatoes, eggplants, and peppers, are highly inflammatory. We’ll come back to the nightshade family, which also includes goji berries …

Old and New Natural Insecticides: We and Our Gut Microbiome Have Evolved to Deal With Some Natural Insecticides, But Not Others

Not all natural insecticides are equally toxic—those in grains, legumes and nightshades are some of the worst because we and our gut microbiome have had less time to adapt to them:

The lectins in beans and other legumes, wheat and other grains, and certain other plants are especially problematic for humans. First, not enough time has elapsed to allow our species to develop immunological tolerance to these substances; nor has sufficient time elapsed for the human gut microbiome to become fully capable of breaking down these proteins.

In Chapter 2, “Lectins on the Loose,” Steven points to four major human dietary transitions that have challenged the ability of human evolution to keep up. (As I noted above, some adaptations, such as being able to digest milk as an adult only require the change of a few genes, other adaptations require the change of many genes.)

CHANGE #1: The Agricultural Revolution.

The advent of the agricultural revolution about ten thousand years ago meant that a totally new source of food—grain and beans—became the dietary staple of most cultures relatively quickly. At that point, the human diet shifted from primarily leaves, tubers, and some animal fat and protein to primarily grains and beans. Until then, the human microbiome had never encountered lectins in grasses (grains) or legumes, and therefore the human gut bacteria, microbes, and immune system had zero experience handling them. …

CHANGE #2: A Mutation in Cows

About two thousand years ago, a spontaneous mutation in Northern European cows caused them to make the protein casein A-1 in their milk instead of the normal casein A-2. During digestion, casein A-1 is turned into a lectinlike protein called beta-casomorphin. This protein attaches to the pancreas’s insulin-producing cells, known as beta cells, which prompts an immune attack on the pancreas of people who consume milk from these cows or cheeses made from it. This is likely a primary cause of type 1 diabetes.6 Southern European cows, goats, and sheep continue to produce casein A-2 milk, but because casein A-1 cows are hardier and produce more milk, farmers prefer them. The most common breed of cows worldwide is the Holstein, whose milk contains this problematic lectinlike protein. If you think that drinking milk gives you a problem, it’s almost certainly the cow’s breed that is at fault, not milk per se. The black and white Holstein is the classic example of the A-1 cow, while the Guernsey, Brown Swiss, and Belgian Blues are all casein A-2. That’s why I recommend that if you consume dairy, you opt for only casein A-2 dairy products, which grocery stores have recently started selling, particularly on the West Coast. Alternatively, use goat or sheep milk products to be safe. …

CHANGE #3: Plants from the New World

It would seem that we should have become pretty tolerant of these new lectins over the past ten thousand years, but let’s take one more trip back in time. Five centuries ago, the last of the major changes in lectin exposure—and perhaps the biggest disruption of all—occurred when Europeans reached the Americas. The explorers brought New World foods back to their native countries, and the Columbian Exchange, named after Christopher Columbus, exposed the rest of the world to a whole array of new lectins. They include the nightshade family, most of the bean family (legumes, including peanuts and cashews), grains, pseudo-grains such as amaranth and quinoa, the squash family (pumpkins, acorn squash, zucchini), and chia and certain other seeds. All are foods that until then no European, Asian, or African had ever seen, much less eaten. 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 bacteria, and your immune system are ill prepared to tolerate them. Getting to know a new lectin in five hundred years is equivalent to speed dating in evolution!

CHANGE #4: Contemporary Innovations

In the last five decades we have faced yet another unleashing of lectins in processed foods and most recently in genetically modified organisms (GMOs), including soybeans, corn, tomatoes, and rapeseed (canola). Our bodies have never before encountered any of these lectins. Moreover, with the introduction of broad-spectrum antibiotics, other drugs, and a vast array of chemicals, we have totally destroyed the gut bacteria that would have normally given us a chance to process these lectins and educate our immune system about them. We’ll discuss these deadly disruptors further in chapter 4.

Comparing Steven Gundry’s Recommendations to a Low-Insulin-Index Diet that Tries to Avoid Too Much Animal Protein

Steven’s recommendations amount to true paleo: paleo that recognizes that our distant African ancestors weren’t eating grain, New World plants, cow milk or processed food, ate fruit only in season and honey quite seldom, and probably had many, many meatless days, other than seafood for those on the coast and quite small animals.

Rewinding the agricultural revolution: With very few exceptions, a low-insulin-index diet already means avoiding grain-based products and beans, as can be seen from the tables in “Forget Calorie Counting; It's the Insulin Index, Stupid.” The one direct exception in my diet was plain oatmeal; I now avoid oatmeal for Gundry reasons even though its insulin index is moderate.

The other big issue is cornfed or in other ways grain fed cattle and chickens. That has involved only a shift to higher quality grassfed beef, chickens allowed to forage, and omega 3 eggs. (If chickens are fed enough omega 3-rich foods to make their eggs omega 3 eggs, that is that much less grain they are being fed.) Farmed fish are also grain fed and it takes a little attention to avoid them, but isn’t too hard otherwise.

Rewinding the Holstein revolution: As I write in “Is Milk OK?” I have been worried about dairy in any case. The cheapest and easiest way to deal with the problems of milk would be to simply avoid dairy. However, I love dairy too much to give it up entirely. Steven has given me hope that some of the evidence for health problems from milk have to do with the A1 protein that arose in what I am calling “The Holstein revolution.”

It is not easy to find milk from cows with only the A2 protein, but Whole Foods does carry A2 cow milk with the brand name “A2” and goat butter (goats and sheep are all A2). In the Boulder area, it is also possible to buy goat milk, unsweetened goat kefir and creme fraiche from French cows, which is more likely to be from A2 cows. The Manchego cheese from Costco that I have recommended is sheep cheese and so is fine, and many restaurants have goat cheese (“chevre”) on the menu. What I still can’t find is liquid A2 cow cream (as distinct from the creme fraiche) or A2 half and half. So I have been combining A2 milk with organic cream from costco that probably contains some A1 protein, though hopefully not too much.

Rewinding the Columbian exchange: To me, the logic behind avoiding New World plants was the most eye-opening element in The Plant Paradox. Many of the nightshades are New World plants, as is corn. Like most people, I didn’t even have “New World plant” in my head as a relevant distinction for diet and health. Whatever you think now about the claim that we may not be well-adapted to eat New World plants, it is worth trying this distinction on for size: try noticing which foods are New World plants and which are Old World plants. Since beginning to read The Plant Paradox, I have found myself googling foods to read about their history. It has been interesting.

Potatoes and corn have a very high insulin index, so I didn’t need to think about Old World vs. New World foods to know I should avoid potatoes and corn—and all the many processed foods made with corn. But avoiding tomatoes was a new idea to me, and something of a sacrifice. I have bulked up my Giant Salad with other vegetables, such as broccoli, cauliflower and bok choy, to compensate. (Steven also recommends avoiding culinary “vegetables” that are botanically fruits, such as cucumbers. For me that wasn’t much of a sacrifice.)

Rewinding the rise of modern food processing: At this point in history, avoiding sugar implies avoiding most processed foods. In addition to the ubiquity of sugar in processed food and the issues I raise in “The Problem with Processed Food”, the dominance of corn in processed food that Michael Pollan points out is another strike against processed food.

Steven also warns against GMOs (“genetically modified organisms). In my life as a whole, I have been a defender of GMOs. I have no objection in principle to genetically modifying the plants for our food. But it matters what genetic modification is being made! Many GMOs are genetically modified to add in genes for natural insecticides! Others are genetically modified so that pesticides can be added externally without killing the plant. So, the point of the most most important genetical modifications so far has been to increase the natural insecticides and make it easier to add pesticides externally to our food chain.


Any dietary change is an adjustment. But beginning from where I was before starting to read The Plant Paradox a few months ago, the benefit/cost ratio for me from going the extra Gundry mile has been excellent.

In addition to the ideas that were new to me in The Plant Paradox—a warning against New World plants, a milder warning against culinary vegetables that have seeds in them and so are botanical fruits (such as cucumbers and squash) and some nuances about dairy—I have noted in The Plant Paradox that Steven Gundry has read the same books I have read and discussed on this blog, and come to many of the same conclusions. There is one big difference: while Steven is very much in favor of fasting, he doesn’t push fasting very hard. I do.

I consider fasting—drinking water, but not eating anything for a period of time—the magic bullet for weight loss. (See “4 Propositions on Weight Loss” and “Magic Bullets vs. Multifaceted Interventions for Economic Stimulus, Economic Development and Weight Loss.”) From reading the Plant Paradox, I realized an additional virtue of fasting: even if we are totally ignorant about something unhealthy in the food we are eating, fasting can give our bodies a chance to heal from the damage caused by those foods.

Sometimes people claim that fasting gives them an unparalleled mental clarity. One way that could be true is that fasting, by avoiding all food, necessarily entails avoiding any specific foods that can cause “brain fog.” If we figure out which specific foods cause “brain fog,” then it could be possible to have that level of mental clarity all the time. In that endeavor, I think Steven Gundry is on to something.

Be sure to also read my post Reexamining Steve Gundry's `The Plant Paradox’.”

Don’t miss my other posts on diet and health:

I. The Basics

II. Sugar as a Slow Poison

III. Anti-Cancer Eating

IV. Eating Tips

V. Calories In/Calories Out

VI. Other Health Issues

VII. Wonkish

VIII. Debates about Particular Foods and about Exercise

IX. Gary Taubes

X. Twitter Discussions

XI. On My Interest in Diet and Health

See the last section of "Five Books That Have Changed My Life" and the podcast "Miles Kimball Explains to Tracy Alloway and Joe Weisenthal Why Losing Weight Is Like Defeating Inflation." If you want to know how I got interested in diet and health and fighting obesity and a little more about my own experience with weight gain and weight loss, see “Diana Kimball: Listening Creates Possibilities and my post "A Barycentric Autobiography. I defend the ability of economists like me to make a contribution to understanding diet and health in “On the Epistemology of Diet and Health: Miles Refuses to `Stay in His Lane’.”