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Quinn on Nutrition: What about lectins?

fava beans

Reader Susan S. writes, in part: “Gut health is finally being brought up in mainstream more often. But almost never this: there are grains, nuts, fruits, and vegetables that have LECTINS that poke tiny holes in our intestines. I thought you might want to check this out so that you can inform your readers. I realize it’s not a simple subject..”

You’re right, Susan, this is not a simple subject.

A recent review on this topic by registered dietitian nutritionist Kristin Sementelli notes: “As with many debates in nutrition science, there’s evidence both supporting and opposing the inclusion of lectins in the diet.”

It’s therefore important, she continues, to fully understand the entire body of research before forming an opinion.

First, what are lectins?

They are a type of protein found in most plants such as cereal grains, legumes and fruit. These proteins are more concentrated in black beans kidney beans, soybeans and whole grains.

Plant specialists say lectins may help plant seeds to sprout. They also help protect a growing plant from fungus and other pests.

Some evidence has emerged, however, that lectins can damage the intestinal tract and lead to inflammation. Some studies even suggest a link between lectins and the development of rheumatoid arthritis. Very few of these studies have been on humans, however. Most have been on rats.

Research also shows that these proteins in plant foods may have some health benefits. Various types of lectins have been shown to fight specific viruses and bacteria and to protect against yeast infections. Lectins are also being studied for their potential to fight off cancer, including (interestingly) cancers of the digestive tract.

All of the studies thus far have been on lectins isolated from the food where they naturally reside.

So, is it a good idea to stay away from healthful plant foods such as legumes and whole grains to avoid lectins? Or can we reap the numerous nutritional benefits from these foods and still protect ourselves from potential problems with lectins?

First, know that simply cooking beans, whole grain pasta or the like inactivates lectins. Certain processes like food irradiation also appear to reduce the lectin activity in plant foods.

Second, remember that the high concentrations of pure lectins fed to rats does not always match what we would normally consume in our diets. For example, one study used the amount that would the equivalent to eating more than 80 slices of whole wheat bread. Clearly more research is needed to figure all this out.

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