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Lectins are proteins in plants that studies have linked to both positive and negative health effects. Some experts have proposed the idea that a diet free of lectins can benefit health, but the available research does not support this claim.

Some plant-based foods — such as beans and legumes, whole grains, and some vegetables — contain a high amount of lectins.

Lectins have some links to inflammation, and researchers have studied excluding them to manage specific health problems, such as multiple sclerosis (MS).

In this article, we look at the research into lectins and the lectin-free diet.

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Research does not currently support any of the alleged health benefits of the lectin-free diet.

Lectins are a type of protein that, in humans, may promote cell development and support communication between cells. They also play a role in the human immune response.

There are several different types of lectins. Some are harmless to human health, while others, such as ricin, can be fatal in small amounts.

Lectins may impact health in multiple ways, ranging from digestion to chronic disease risk. Research has also shown them to cause clustering in red blood cells.

Some doctors categorize them as antinutrients, as they block the absorption of some nutrients.

The type of lectin present in red kidney beans is called phytohemagglutinin. It is responsible for red kidney bean poisoning, which results from eating raw or undercooked kidney beans. According to the Food and Drug Administration (FDA), consuming just four raw kidney beans could cause symptoms such as severe nausea, vomiting, and diarrhea.

If a person has enzymes that do not function correctly, consuming excess lectins may lead to nutrient deficiencies and digestive problems. This is because the body cannot break down lectins. Instead, they bind to nutrients and the cells lining the gastrointestinal tract.

However, lectins often attach to carbohydrates and leave the body before they can cause harmful effects.

This action on carbohydrates has led to some test tube studies that suggest that lectins might affect the growth of cancer cells.

The nutrients that accompany lectins in plant-based foods are also essential. Removing them from the diet may have damaging consequences.

Researchers are even looking at lectins as potential treatments for illnesses caused by bacteria, fungi, and viruses.

Dr. Steven Gundry coined the term "lectin-free diet." Dr. Gundry is a former heart surgeon who switched his focus to food and supplement-based medicines.

He describes lectins as the main danger in the Western diet. He has therefore written a book that provides information on how to avoid lectins, alternative food choices, and recipes.

According to the book, Dr. Gundry's plan helps people improve their health and reduce their body weight.

However, no evidence supports the exclusion of lectins from the diet outside of condition specific diets.

For the majority of people, the health benefits of a lectin-free diet are not clear.

However, removing lectins from the diet has proven helpful for groups of people with specific conditions.

For example, a 2019 review of studies highlighted the fact that a lectin-free diet may benefit people with inflammatory bowel disease and MS.

However, research has not yet confirmed its benefits for the wider population.

The lectin-free diet is a restrictive plan, which may make it difficult for some people to follow it long-term. The plan also limits or eliminates many nutritious foods, such as whole grains, beans, and certain vegetables.

A 2016 review of 45 studies showed that consuming whole grains can help reduce the risk of overall mortality and several conditions, including heart disease, diabetes, and various cancers.

Fruits and vegetables also have many health benefits. Eating fruits and vegetables may lower the risk of several conditions, including heart and lung diseases. These foods may also impact cancer risk and help prevent weight gain.

A lectin-free diet may be difficult for vegetarians or vegans to follow, as legumes, nuts, seeds, and whole grains provide plant-based protein.

Legumes, whole grains, and fruit and vegetable peels also provide dietary fiber. A lectin-free diet could result in constipation if a person's dietary fiber intake decreases.

Also, following a lectin-free diet may be expensive, as the plan recommends specialty milk, pasture-raised meat, and expensive supplements.

Dr. Gundry recommends the following foods for people who wish to limit their lectin intake:

According to Dr. Gundry, people may wish to limit the following foods when trying to avoid lectins:

  • squash
  • legumes, including beans, peas, lentils, and peanuts
  • nightshade vegetables, such as eggplant, peppers, potatoes, and tomatoes
  • fruit, although the diet allows moderate amounts of in-season fruit
  • grains

If a person wants to consume grain, the plan recommends products made from white flour instead of wheat.

Dr. Gundry suggests completely avoiding the following foods:

  • corn
  • meat from corn-fed animals
  • A1 milk

Although lectins may cause some damage for people with an intolerance or if people eat them in excess, there is strong research to support the benefits of eating plant foods.

Some people with MS or inflammatory bowel disease may benefit from limiting lectins in the diet. However, the current evidence does not support this diet as a general tool for managing body weight.

Many plants are high in lectins. However, lectin levels can differ significantly between plant types. There are also many kinds of lectins, and some seem to provide health benefits.

It is also important to note that much of the research into lectins has been via animal or test tube studies. No recent research supports excluding them from most diets. Furthermore, many studies have looked at single lectins instead of the foods that contain them.

More research is necessary before doctors can recommend following a lectin-free diet. At this point, it seems to be more of a dieting trend than a plan with well-documented scientific support.

Q:

How can I prepare lectin-heavy foods, such as kidney beans, in a way that reduces the risk of poisoning?

A:

Lectins are most potent in their raw state. Therefore, cooking lectin-rich foods at high temperatures can dramatically reduce their content.

Boiling or stewing legumes, for example, gets rid of almost all of the lectin content. Soaking beans before cooking them is also effective.

However, raw beans simmered at slow and low heat, such as in a slow cooker, will likely not remove the lectins effectively.

Natalie Olsen, R.D., L.D., ACSM EP-C Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.