4 Things to Know About the “New Gluten”: Lectins

July 19, 2017
By: Anna Pashkova, ACSM EP-C

legumes lectins

By now, most of us are aware of the growing trend of going gluten-free. More recently, a “lectin-free” diet is being promoted. This diet suggests that we should avoid whole grains, legumes, seeds, nightshade vegetables (tomatoes, eggplant, potatoes, etc.), out-of-season fruit, dairy and eggs. You may be thinking, “what can you eat?”. While some people truly need an avoidance diet for specific conditions, any diet that eliminates so many nutrient-rich foods should be critically and fully explored before jumping on the bandwagon.

Here are 4 things you should know about lectins:

1. Lectins are a type of protein, which exists in many different forms and have many different functions, both good and bad.

Lectins are a group of proteins that bind to carbohydrates and exist in most plants. They can have both beneficial and harmful effects. Lectins are naturally used by plants to protect themselves from predators and cause unpleasant symptoms to deter those predators. They also exist in the human body and function as a helpful member of our immune system. The harmful effects of lectins have been the focus of the lectin-free diet.

 2. Some lectins are toxic, such as in raw or undercooked kidney beans, but proper cooking reduces this toxicity significantly.

Many lectins in our diet are harmless because they are denatured during cooking...      

Many lectins in our diet are harmless because they are denatured during cooking and broken down by our digestive system. Eating raw or undercooked legumes (beans, lentils, etc.) can cause symptoms such as vomiting and diarrhea, but when was the last time you had raw beans? The reason uncooked lectins are more dangerous is because they are very stable to proteases in the body. When cooked, they are more easily digested by these proteases. According to this study, most, if not all, lectins can be removed by boiling beans for 30 minutes. Soaking beans will also help remove lectins, but they should still be boiled for 30 minutes when cooking. Canned beans also have very low lectin levels due to the canning process.

Grains contain lectins, but we also boil our grains before eating them. Other ways to reduce lectin levels in foods include fermenting and sprouting - another great reason to eat those delicious probiotic-rich foods! Steaming and cooking vegetables also reduces lectin levels, if you are concerned about the lectin contents of these foods.


 3. Proponents of a “lectin-free” diet claim that lectins may cause digestive issues, leaky gut, bloating, nausea, gas and diarrhea, but the cited study (Peumans & Van Damme, 1995) only states that these effects occur in humans when consuming raw or undercooked beans.

First, these symptoms could be caused by a variety of reasons, not just lectins. Second, the research that this is based on is from 1995 and only mentions the harmful effects of lectins on human consumption only when consuming raw or undercooked beans. Another study states that foods with high concentrations of lectins, such as beans, cereal, grains, seeds, nuts and potatoes, could be harmful if consumed in excess if uncooked or improperly cooked. The effects of consumption include nutritional deficiencies due to their anti-nutrient properties and immune reactions. Again, this is regarding consumption in excess and of uncooked or improperly cooked foods.

 4. The majority of lectin studies have been conducted in isolated lectins rather than real food and on animals or in test tubes, not people.

In addition to this, research has also shown beneficial effects of lectins due to their antimicrobial, anticancer and immune system properties. A fair amount of research is currently showing that plant lectins may be a potential tool against cancers, especially digestive cancers. Because of this, it’s difficult to know how various types of lectins affect the human body after they are cooked and digested from real foods. Many of the high lectin foods, such as cereals and whole grain products, have also been shown to significantly reduce the risk of type 2 diabetes, cardiovascular disease, cancers, and help with long term weight management. These benefits of high lectin foods are better established than the effects of lectins after cooking in humans.

Conclusion –

While lectins do exist in many of the foods we eat and some do have toxic effects, most of these effects are eliminated by proper cooking and are safe for consumption in normal amounts. Legumes and whole grains are rich sources of B vitamins, iron and fiber while vegetables and fruits are powerhouses for a wide variety of micronutrients. Although avoidance diets may be necessary for some people with specific conditions, they may not be the best for the general public. If you are seriously considering an avoidance diet, it’s always best to consult with a Registered Dietitian to avoid any nutrient deficiencies, which could cause a multitude of other problems.

What are your thoughts on the rise of lectin-free diets?  Please share in the comments below.