Lectins and the Plant Paradox

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Over the last couple of months, I have gotten hundreds of questions from readers and listeners about a book calledThe Plant Paradox by Dr. Stephen Gundry. In it, Gundry claims that there’s a toxic compound in our food supply that may be “the cause for most common health problems.”

There are an awful lot of people writing about food and nutrition these days. It can be hard to be heard above the din of so many experts and celebrities and marketers. Finding a “hidden danger” is a tried and true way to get attention, especially if you can reveal a previously unknown threat lurking in foods that are thought to be good for you.

And that’s exactly what Gundry claims to have uncovered. It’s not fast food, added sugars, or highly processed food that’s causing our problems, he suggests. It’s not a pesticide, preservative, or plasticizer. The real cause, he says, is “so well hidden that you would never have noticed it.”

Well, he certainly has my attention. How about yours?

The culprit, Dr. Gundry says, is lectins. And where are lectins found? In vegetables, fruits, whole grains, nuts, seeds, and legumes. Could it be that the very foods that are supposed to be the foundation of a healthy diet, the foods that we are constantly encouraged to eat more of, are actually making us sick?

Lectins are not a single compound but an entire class of proteins that have a propensity to bind with carbohydrate molecules. We’re not sure exactly what the function of lectins in plants might be. They are widespread in plants but they are particularly concentrated in seeds. They might have something to do with helping preserve the viability of seeds until conditions are conducive to germination.  

The human diet has always contained a wide variety of lectins. In fact, lectins perform a variety of functions in the body, including participating in our immune response. Certain lectins are being studied for their potential role in protecting us from cancer.

A few specific lectins, such as those found in raw kidney beans, are known to be quite toxic to humans. As few as half a dozen raw kidney beans can create severe food poisoning symptoms. Another lectin found in wheat germhas been shown to make lab rats really sick. However, you’d have to eat about 200 pounds of raw wheat germ to get as much lectin as these poor rats were fed. That’s a lot of wheat germ. But most lectins appear to be harmless. Or at least they did, until Dr. Gundry came along.

Dr. Gundry recommends a low-lectin diet, which means avoiding beans and legumes, including soy and peanuts, as well as corn, squash, tomatoes, peppers, and eggplant. Whole grains are discouraged. To the extent that you eat grains, Dr. Gundry recommends choosing foods made with white flour.

Unlike Dr. Gundry, I think you are better off eating whole grains than refined grains. However, I do believe that even whole grains should be eaten in moderation. But this is not due to concern over lectins. For more on why, see “The truth about whole grains.”

The evidence implicating lectins in human disease or demonstrating the benefits of avoiding them is pretty thin. Gundry says his own patients have been cured of everything from cancer to heart disease. However, no credible published research exists to support the therapeutic benefits of a low lectin diet. In fact, the evidence that we do have seems to point in the opposite direction.

There is a lot of research showing that people who eat morewhole grains, legumes, fruits and vegetables (and presumably take in more lectins) have lower risk of disease.

People who suffer from digestive disorders such as Crohn’s disease or Irritable Bowel Syndrome often do better when they reduce their intake of legumes and whole grains. And because a low-lectin diet would largely eliminate these foods, it might help with IBS symptoms...but the baby is being thrown out with the bathwater.

I’ve talked before about the low-FODMAP diet for IBS, which, unlike the lectin-avoidance diet, has published clinical research to support it. A low-FODMAP diet does limit beans and some (but not all) whole grains. It does not restrict your intake of vegetables like tomatoes and peppers. That’s because the goal is not to reduce lectins but to reduce certain classes of carbohydrate that appear to be responsible for a lot of digestive distress.