The Carnivore Diet Revolves Around Avoiding Lectins. They May Be a Surprising Key to Health.

Sam Westreich, PhD

Poisonous lectins? Anti-nutrients? Do we still not know how to properly EAT?
According to carnivores, the worst thing in this picture… is the lettuce?Photo by Szabo Viktor on Unsplash

Did you know that there are people out there who aim to be carnivores, in the literal definition of the word? Most of us, if we aren’t vegetarians, are omnivores — eating both meat and vegetables.

But some believe that vegetables are actually terrible for us. There’s a growing number of believers in the “carnivore” diet, who argue that we should be eating all meat, all the time. Vegetables are the enemy.

One of the biggest dangers, according to proponents of this diet? A class of proteins that bind to carbohydrates, called lectins. All-meat diet fans say that lectins are toxic, and argue that we are poisoning ourselves whenever we eat vegetables because we’re ingesting these anti-nutrients.

Lectins, they claim:

  • cause nausea, vomiting, diarrhea, bloating, and gas
  • bind to red blood cells to make them clump together in clots
  • bind to nutrients like calcium, iron, phosphorous, and zinc, preventing them from being absorbed into the body
  • bind to intestinal cell walls, blocking nutrient absorption and triggering immune reactions
  • may trigger auto-inflammatory reactions like rheumatoid arthritis and type I diabetes

That’s a long list of nasty side effects. Is this really the case? Should we be avoiding lectin-rich plants?

The short answer: no.

The full answer, however, is a bit more complex.

Lectins are poisonous, but…

First, this isn’t all bullshit. Yes, plants really do contain lectins, and yes, lectins are toxic if consumed in large quantities.

Lectin levels are especially high in foods like:

  • kidney beans
  • peanuts
  • whole grains
  • potatoes
  • soybeans
  • tomatoes

Why would these plants produce lectins? Lectins serve a couple of different functions; they act as a defense against insects and other predators that would eat the plant. When an insect eats lectins, they bind to the bug’s gut structures, preventing the insect from absorbing calories and causing starvation and death.

Lectins also aid in attracting the right types of bacteria to plant roots to fuel nitrogen fixing. For some plants, like peanuts, lectins in the roots help bind bacteria onto root nodules, where the bacteria can “fix” atmospheric nitrogen to produce nitrite, a powerful plant fertilizer.

While lectins were likely evolved by plants as an insect defense, they also do work on people. Lectins are poisonous for us; they don’t offer any nutritional value and can induce vomiting and other food poisoning symptoms if consumed.

That sure sounds like it agrees with the stance of carnivore diet proponents. Lectins are poisonous!
Keep them out of your mouth!

But aren’t beans and legumes supposed to be healthy? Why aren’t all these vegetarians keeling over with lectin poisoning?

…but only when consumed raw

See, here’s the part that is left off of most rants about lectins; they are very easily removed.

You wouldn’t eat an ear of corn with the husk still on it, would you? Or the tough outer skin of a pineapple? We need to properly prepare these foods, and lectin-rich foods are no different.

Lectins are primarily present in the outer surface of foods, since this is, naturally, the first area that would be attacked and eaten by insects. They’re also water soluble, likely to help ensure that, once consumed by an insect predator, they can detach and reach the areas of the gut where they do their damage.

For us humans, this makes lectins easy to address. We can soak our lectin-rich beans in water, removing the water-soluble lectins when we drain the water away. Or, if we cook the food, the lectins break down and degrade.
These beans are no longer going to murder you, thanks to the amazing power of boiling them for a little bit.Photo by Artur Kornakov on Unsplash

Yes, if you were to eat raw kidney beans, raw potatoes, raw soybeans, or raw whole grain, you could get sick from taking in too many lectins. But unless you are in a famine situation and are eating these foods raw because you have no other options or methods to cook them, this isn’t going to come up.

For most of us, who have running tap water and a stove, we will remove the lectins from our food through the natural method of preparing them.

In fact, low - but consistent - lectin levels may actually be good for us

To put another hole in the carnivore diet argument, lectins may actually be beneficial for us to consume — at least at low levels.

Lectins act as antioxidants, helping to reduce damage that may be caused by free radicals to our cells. They also slow down the absorption of carbohydrates, which can help prevent spikes in blood sugar that would otherwise occur if the carbs are absorbed quickly.

Foods that are high in lectins are also usually high in another very important nutrient: dietary fiber. Dietary fiber is a long-ignored ingredient that may turn out to be a secret weapon for health; it’s not just roughage that cleans out your intestines, but also serves as a primary food source for many of the microbes that colonize a healthy gut, to create a better and more balanced gut microbiome. Most Americans barely manage to eat half of the recommended amount of daily dietary fiber.

Missing out on fiber-rich foods like beans because of lectin fears? It’s both ill-founded and bad for your health, since you’re avoiding a rich source of fiber.

People who eat large amounts of lectin-containing foods — legumes, whole grains, and nuts — are not doing worse than the general population. Indeed, they show lower rates of obesity, heart disease, and type II diabetes. If these people were being crippled by lectins, they’d be doing worse than the general population — not better.

In summary: don’t fear the lectins

Some pseudoscience diet books create a “boogeyman anti-nutrient” in vegetables, calling out lectins as the poison responsible for many ills and ailments. They’re being deceitful; lectins are bad for us in high quantities, yes — but lectins are removed through soaking in water and through cooking, meaning that they are discarded in the preparation process for most foods that contain them.

Low but regular levels of lectins may be beneficial for us — and the foods that contain lectins are also rich in other nutrients and dietary fiber. A diet high in lectin-containing foods is healthier, based on population studies, rather than less healthy.

And you know what food is very low in microbiome-aiding dietary fiber? Meat. People on the carnivore diet are going to be crippling their microbiomes by eliminating fiber from their diet.

Overall, we should be aiming to eat less meat in general — production involves cruelty to animals, it’s terrible for global warming, it’s less efficient than vegetable production, and it’s not great for us, health-wise.

But if someone starts talking about the dangers of lectins, be alert. It’s likely going to be incorrect.

Have you ever read about the carnivore diet, or the dangers of lectins?


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A microbiome scientist working at a tech startup in Silicon Valley, Sam Westreich provides insights into science and technology, exploring the strangest areas of biology, science, and biotechnology.

Mountain View, CA

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