Revenge of the Beans: How Lectins Suck Your Energy And Make You Weak

Revenge of the Beans: How Lectins Suck Your Energy And Make You Weak

As you check out the new Bulletproof® Diet infographic (just posted in advance of the Bulletproof® Diet book launch!) you’ll notice that lentils and beans, as well as some other foods like tomatoes and potatoes, are out of the green zone. There’s a reason!

This is one area where the Bulletproof Diet does not match the Slow-carb diet recommended by Tim Ferriss in the 4-Hour Body. People often ask why they should avoid these foods. So here’s the science behind the diet…

Lectins 101: Why lentils, tomatoes, and potatoes make you weak

Some Bulletproof Diet recommendations are based on the presence of lectin in foods. Be sure to realize that lectin is not the same as leptin, the hormone that controls whether you’re fat, or lecithin, a type of fat found in eggs, sunflowers, or soy. If those similar names aren’t confusing enough, lectin has an impact on leptin too.

Lectins matter to the performance level of everyone, but they are particularly important if you have a thyroid condition, or if you have any kind of arthritis, diabetes, heart disease, cystitis, or even if you are simply 100 pounds overweight (like I was). This is because lectins are tied directly to inflammation and autoimmune reactions in your body.

Lectins are a form of protein found in nearly all plants and animals. They bind to the sugar molecules called polysaccharides that cover the surface of most cells in your body.

There are countless varieties of lectins in nature, and we have used them for more than 100 years in medical testing laboratories because they stick to red blood cells very effectively.

Plants evolved to reproduce. They actually have no interest in being a food source for you, or even for insects or fungi. Since they are not good at running away, plants developed natural pesticides and repellents to protect themselves and their seeds from hungry animals.  Since the cells in your body use lectins as one way to communicate between each other, plants evolved to create their own lectin to “hack” the human cell communication by disrupting it. Does this make plants the original biohackers?

The Evil That Beans Do

Take kidney beans, for example. Only a few raw kidney beans can kill you because the naturally occurring lectins will bind to the sugar coating on your red blood cells, which makes them stick together until you get abnormal clotting.

Perhaps you’ve heard of ricin, the extremely toxic poison featured in the Breaking Bad TV series. Vanishingly small doses will kill you, yet it is derived from the lowly castor bean. At the hospital, doctors test your blood type based on how your blood reacts to different types of lectins. And inexperienced cooks learn how lectins cause bloody vomiting.1

The toxicity of lectins is known to food safety experts, but you never hear about it in popular nutrition circles. It’s no surprise that the top 8 food allergens contain higher amounts of lectins, including: dairy, eggs, wheat, soy, peanuts, tree nuts, fish, and shellfish. In fact, about 20% of all cases of rheumatoid arthritis are caused by lectins in the nightshade family. Common nightshades include tomatoes, potatoes, eggplant, and bell peppers. There are perhaps 100 additional less common foods like goji berries in that family, all of which contain lectins. “Superfood” goji berries anyone? Think again.

Use Glucosamine to Bind Lectins and Improve Joint Health

Different lectins love different sugars in your body’s cells. One of the reasons wheat is so bad for you is that the lectin in wheat is attracted to glucosamine, the polysaccharide that covers your joints. You can buy glucosamine to help your joint health. It doesn’t work for some people, but for others, it’s magic. I was one of those who had constant knee pain until my mid-twenties, and my knees were always inflamed even after three surgeries. Glucosamine dramatically reduced the inflammation and pain. I had not fully embraced a zero-gluten diet, which is the most likely reason it was so helpful for me. The glucosamine in my supplements was binding the lectin in my diet before it reached my joints!

The most effective form of glucosamine for binding lectin from wheat is N-Acetyl-D-glucosamine. It’s not impossible to find in supplements, but if you have read this far, you already know that wheat is simply not a food for high-performance humans. I do not use glucosamine regularly today.

Several More Problems with Lectins

If you are still not convinced that you should avoid the more toxic lectins, check out what happens when you add lectins from edible plants, including lima beans and kidney beans, into the diets of rats.2 Scientists who did this found depressed growth, pancreas enlargement, depressed insulin, and disruption of normal protein, fat, and carbohydrate intermediary metabolism. The researchers hypothesized that it was most likely due to the hormone mimicking actions of lectins (although it may have been also related to enzyme inhibitors found in legumes). Either way, it’s not Bulletproof.

It’s not just beans, either. Gliadin is a component of wheat gluten that can activate inflammatory NF-kappa beta proteins, the ones involved in a myriad of acute and chronic inflammatory disorders, including autoimmunity and infectious diseases. High performance people avoid things that make you weak, like autoimmune conditions and rampant inflammation. One more reason to avoid wheat…

Then there’s leptin, the hormone that signals when you’re full. When your metabolism breaks, you get resistant to leptin before you get insulin resistant, and both forms of resistance lead to obesity. Guess what? Lectin is associated with leptin resistance.3

GMO foods are not on the Bulletproof Diet for lots of reasons. One primary reason is that the genes inserted into crops often increase the amount of lectin, and add new lectin to GMO strains. Lectins are one reason that GMO foods are more allergenic than non-GMO foods.

Perhaps most insidious of all is that lectins cause leaky gut.4 When they damage the lining of your gut, other proteins from food you eat enter your bloodstream and program your immune system to attack other parts of your body. That means you may have cross-reactivity with your nervous system tissue, your heart, your skin, your thyroid, or even your brain.

I believe that excessive lectins from my careful former raw vegan diet contributed to the large increase in food sensitivities that I experienced as a vegan. There are dozens of former vegans who have written in to the Bulletproof site expressing similar experiences. Lectins are not the sole cause – toxins from mold, another anti-nutrient, also may play a role.

Autoimmune conditions and associated inflammation are tied to IBS, colitis, Hashimoto’s thyroiditis (I fixed mine by avoiding grains, molds, and many lectins), Chrohn’s, fibromyalgia, and chronic fatigue syndrome, in addition to different forms of arthritis. There is even a link to autism and its little brothers, Asperger syndrome and ADHD.5 It’s no wonder that people with ADHD love the Bulletproof Diet.

I learned a lot of these things when I bought a college level biochem book about 7 years ago, called Plant Lectins (Pusztai, Cambridge University Press, 1991).6  In it, the authors cite a study from 1980 showing that 30% of fresh and processed foods contain lectins. Lectins from green salads, fruits, spices, seeds, dry cereals and nuts showed lectin activity, and some of them interact with blood serum or saliva and bacteria from the oral cavity. Ever noticed excessive salivation, or extremely thick saliva after a meal? Now you know why.

FAQ: Why is Butter Ok but Dairy is not?

If you are reading carefully, you probably noticed that dairy is high in lectin. However, grass-fed butter, a staple of the Bulletproof Diet, is not! Grain-fed milk is higher in lectin than grass-fed milk. Pasteurized, homogenized milk (the stuff I recommend you avoid) has less SIgA, an immunoglobulin that is present in raw milk. SIgA binds to dangerous lectins.  This is why I recommend you consume raw dairy, but only if you tolerate it.

Dealing with Lectins

The most obvious thing to do is to not eat high carbohydrate foods that also contain lectins, which you already do while on the Bulletproof diet. Also, limit lower carbohydrate high lectin nightshades, and test your response to them with your iPhone using the free Bulletproof Food Sense app.

The next best thing is to mechanically remove the parts of the food that have the most lectin in them.  This is why, throughout history, the higher economic classes would choose white rice over brown rice and white flour over whole wheat. Not that you should ever eat gluten if you are a high performer, but if you did, now you know why to choose the white flour! This is also one reason why white rice is ranked higher than brown rice on the Bulletproof Diet. Who needs extra fiber when it’s wrapped in lectin?

Historically, people have used a variety of techniques to try to reduce these food toxins. Cooking sometimes helps, but some lectins are made stronger, such as red kidney beans, which become 5 times more toxic when heated to 80 degrees Celsius.7 Dry heat doesn’t work very well to break down lectins, which is why baking with “gluten free” garbanzo bean flour is a bad idea. The best cooking method to destroy lectins is pressure-cooking.

You could also try fermenting. The only problem is that when you allow bacteria to breakdown proteins, including lectins, you get the creation of histamine, which triggers allergies. Oops. Still, it’s better to allow bacteria to digest the lectin than it is to allow it in your body. This is why, if you must eat soy, you should stick with fermented soy like miso, tempeh, tamari, and natto. But the histamine and phytoestrogens in soy, fermented or not, should keep you away if you read this blog! As far as I can tell, no one has ever written about how soaking to reduce lectins can increase histamine, and improper fermentation techniques can cause the formation of mold toxins.

Then there’s soaking and rinsing. Your grandmother probably soaked beans overnight, then rinsed and boiled them again, possibly with baking soda. She might have done this so you, her lovely grandchild, would have less intestinal gas, but the reason for this effect was that she was removing some lectins.


One of the reasons people rely on the Bulletproof® Diet infographic is because you don’t need to know any of the details in this blog post in order to take advantage of them.  This knowledge is built in so that if you are choosing foods in the green zone, you are automatically choosing to eat less lectin.

That said, biohackers like me want to understand how and why things work. So now you know!


  1. Beware of the Beans: How beans can be a surprising source of food poisoning
  2. Lectins, by Halina Lis
  3. Agrarian Diet and Diseases of Affluence
  4. Ibid.
  5. Intestinal Pathophysiology in Autism
  6. Plant Lectins, Pusztai A., Cambridge University Press (1991).
  7. Bad Bug Book: Foodborne Pathogenic Microorganisms and Natural Toxins Handbook

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