What Is a Lectin-Free Diet?

Medically reviewed by Natalie Olsen, RD, LD, ACSM EP-C on August 21, 2017Written by Corey Whelan

Overview

Lectins are a type of carbohydrate-binding protein, which stick to cell membranes in the digestive tract. They exist in most plant and animal foods. However, they’re found in the highest amounts in legumes, nightshade vegetables, dairy products, and grains, such as barley, quinoa, and rice. Some types of lectins, such as ricin, are toxic, but others are not.

There is limited research on how lectins affect people. The lectin-free diet promotes reducing lectin intake or completely eliminating them from your diet. This may be beneficial for some people with food sensitivities. However, more research is still needed.

Is it good or bad for you?

If you don’t include a variety of nutrients in your diet, it may negatively impact your health. On the other hand, if you have food sensitivities or are prone to gastrointestinal distress, avoiding foods with lectin may be beneficial.

Lectin has not been studied extensively in humans. Currently, there is no evidence that can conclude whether it’s good or bad for your health. The lectin diet is restrictive and eliminates many foods — even those thought to be healthy.

Benefits of the lectin-free diet

It may benefit people with food sensitivities

Eating large amounts of food containing lectin may cause gas or gastric distress in some people. Lectin is not digestible. It binds to cell membranes lining the digestive tract. There, it may disrupt metabolism and cause damage.

It can help you to avoid potentially toxic foods

Cooking destroys most lectin in food. It is important to avoid raw, soaked, or undercooked beans, such as kidney beans, which have been found to be toxic to people due to their lectin levels. According to one study reported in the South African Medical Journal, soaking beans is not enough to remove lectin content.

It might reduce peptic ulcers

An animal study showed the negative effects of lectin in rats. It spiked bacterial growth in the small intestine and stripped away the mucous defense layer. This increases the risk of peptic ulcers.

It may help you avoid damage in your digestive tract

Some research notes that lectin can disrupt digestion and cause intestinal damage if eaten in large quantities over a prolonged period of time.

Risks of the lectin-free diet

Data from human studies is lacking

Research on lectin, and its effects on people, is currently sparse. Most of the studies have been conducted on animals, not humans. Research has been largely performed in vitro. This means it has been conducted with isolated lectins in laboratory dishes or in test tubes.

The claims may be biased

Approach your lectin research with a healthy dose of skepticism. Look for science-based evidence instead of inflated claims on websites that sell cookbooks, or supplements, geared toward helping you achieve lectin-free health. Some may be what they claim to be, but others may not. For example, there are claims that lectin promotes weight gain, but multiple studies, such as one on pulse consumption, indicate a positive weight loss effect.

The diet is lacking in broad-based nutrition, including fiber

Many healthy foods are prohibited on the lectin-free diet, making it hard to stick to. This food plan lacks many of the nutrients needed for optimum health.

Foods to eat on a lectin-free diet

All plants, and animal products, contain some lectin. Fruits and vegetables on the low end of the lectin scale include:

  • onion
  • broccoli
  • cauliflower
  • mushrooms
  • pumpkin
  • sweet potato
  • carrots
  • asparagus
  • cherries
  • apples
  • blueberries
  • strawberries
  • oranges
  • lemons
  • cherries

You can also eat all forms of animal protein, such as fish, beef, chicken, and eggs. Fats, such as those found in avocados, butter, and olive oil, are allowed on the lectin-free diet.

Foods to avoid on a lectin-free diet

Foods highest in lectin include:

  • nightshade vegetables, such as tomatoes, potatoes, goji berries, peppers, and eggplant
  • all legumes, such as lentils, beans, peanuts, and chickpeas
  • peanut-based products, such as peanut butter and peanut oil
  • all grains and products made with grain or flour, including cakes, crackers, and bread
  • dairy products, such as milk

Diet guidelines and tips

  • If you feel that going lectin-free is for you, you’ll want to make sure to avoid foods high in lectin every day.
  • You can also prepare foods that contain lectin in a pressure cooker, which may help reduce levels.
  • Soaking and boiling beans can help reduce their lectin content.
  • Fermenting or sprouting grains and beans can also help to reduce their lectin content.
  • It may make sense to take a trial-and-error approach to see if you feel better or experience a reduction in gastric distress by removing some foods, but not others.
  • Many of the foods that are eliminated on this food plan are high in dietary fiber, which is beneficial to health. Make sure to eat enough fruits and vegetables to compensate, or take a fiber supplement.
  • It may help to discuss the diet with your doctor, or with a dietitian, prior to proceeding. This will help to ensure that you get the full range of nutrients you need every day.

The takeaway

The lectin found in raw beans is dangerous to humans and can be deadly. Most foods contain some amount of lectin, but those highest in this carbohydrate-binding protein are nightshade vegetables, legumes, and grains. Scientific research on lectin is lacking in humans, but there are some animal studies which indicate that a lectin-free diet might be beneficial for some people, such as those with food intolerances. Make sure to take a skeptical approach when researching this food plan — many websites that promote it are trying to sell products.

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