The Lectin-Free Diet: Fact or Fiction?

September 5, 2019

By Anna Varriano

It seems that every other day, some new theory surfaces in the nutrition world. Sometimes these theories are foundational to overall good health, but most of the time, they end up being just another fad. A recent theory that is getting a lot of attention is the numerous health benefits of a lectin-free diet. While I am no guru on this topic, I’ve read a lot about it. In this blog, based on my understanding and clinical experience, I’m going to cover the following:

  • what lectins are
  • the health pros and cons related to lectins
  • what foods are high in lectins
  • the health claims associated with a lectin-free diet
  • if a lectin-free diet could be the yellow brick road to good health and longevity

Lectins – What Are They?

Lectins are a type of plant protein found in all kinds of foods – particularly legumes, whole grains, and nightshade vegetables (e.g. potatoes, tomatoes, eggplants, and peppers). They can bind to components of cell membranes and play an important role in immune and inflammatory responses.

From a nutrition standpoint, lectins are most commonly found in the seeds of plants. They protect plants against harmful micro-organisms, insects, and other pests, and help the plant’s seeds to stay intact as they pass through an animal’s digestive system. This means the seeds can get scattered through the feces of animals that eat the plant. Mother Nature is one smart cookie.

Health Pros and Cons Related to Lectins

Since humans don’t digest lectins, they may enter our bloodstream unchanged, and if this happens, our immune system sometimes produces antibodies against them. It appears that some individuals can develop food intolerances to certain lectin-containing foods; however, this typically occurs due to an existing immune system and gut health imbalance rather than simply as a result of eating lectin-containing foods (note that gut health and immune system health go hand-in-hand).

While some lectins are toxic in small amounts (e.g. the lectins found in raw red kidney beans … can’t say I’ve ever eaten raw red kidney beans … you?), other lectins have been shown to offer important health benefits. In humans, lectins are thought to play a role in healthy immune function, cancer prevention, proper cellular development and function, as well as inflammation and body fat regulation. I have read articles stating that:

  • lectins in mushrooms, buckwheat, and fava beans prevent cancer
  • lectins are effective against several types of bacterial, viral, and fungal infections
  • many lectin-rich foods are used as therapeutic treatments in Ayurvedic Medicine and Traditional Chinese Medicine – both of which have been in practice for thousands of years

Although lectins are found in a wide variety of foods, many of which have been around for centuries, including among cultures known for outstanding health and longevity, they’ve come under fire lately as a hidden source of numerous health issues.

Lectins have also been labelled as anti-nutrients; that is, substances which compromise the body’s ability to absorb certain nutrients. Some sources state that lectins may contribute to increased gut permeability (aka ‘leaky gut’). When this happens, bits and pieces of undigested protein inside the small intestine can enter the bloodstream. Since these undigested bits and pieces shouldn’t normally be able to get into our blood, the body may view them as invaders and launch an immune response against them. It could be a benign allergic reaction, and/or with repeated exposure, it could set the stage for the development of an autoimmune disease such as rheumatoid arthritis, Type 1 diabetes, multiple sclerosis (MS), or inflammatory bowel disease (IBD).

It’s interesting to note that the majority of lectin studies quoted in respect to the negative health effects of lectins have been done with isolated lectins, not the whole food containing the lectin – which is how we would normally consume lectins –  and the studies have been conducted in test tubes or on animals, not on people.

Regardless of the lack of proper research on the topic, many prominent on-line health gurus are painting all lectins with the same brush and focusing all the attention on the potential negative effects of lectins. In my opinion, saying that we should avoid all lectin-containing foods because they may cause problems is like saying we shouldn’t drink any water because drinking water from a still pond will make you sick. It’s the dietary equivalent of throwing the baby out with the bath water.

Foods High in Lectins

Below is a list of foods that are typically cited as being high in lectins, as well as my comments on each of them.

Legumes – especially raw – especially raw beans – especially raw red kidney beans. I don’t think many people eat raw beans on a regular basis! Luckily, cooking methods such as boiling or stewing effectively deactivate lectins. While I’ve read you should boil beans for 30 minutes, I’ve also read that boiling certain beans for as little as 5 minutes virtually eliminates all lectin activity.

Grains – especially wheat germ. Grains can also be sprouted or boiled (think rice and barley) to reduce lectin content. I’m a fan of soaked and sprouted grains, as soaking/sprouting reduces lectins and other anti-nutrients. I think most people eat too many grains and grain products in general (e.g. breads, crackers, cereals, cookies, etc), so reducing grain consumption is a good idea for most folks.

Squash  –  I often recommend squash and pumpkin to promote intestinal health. I typically don’t eat the seeds and peels, which is where the lectin is concentrated, and I bet most people don’t either. Squash is loaded with health-boosting nutrients! You can learn more about them here!

Milk – especially commercial cow’s milk. I don’t promote commercial cow’s milk for a number of reasons, primarily because of how the cow’s are raised and how the milk is processed/denatured through pasteurization and homogenization. We don’t need dairy to be healthy (even Health Canada agrees, having eliminated ‘Milk & Alternatives’ as a food group from the latest version of the Canada Food Guide), although fermented dairy like whole fat, plain, organic yogurts and kefirs (made with grass-fed milk if you can find it) is a good source of probiotics.

Vegetables and fruits – especially vegetables from the nightshade family (potatoes, tomatoes, bell peppers, eggplant). Interestingly, while there are no long-term studies related to the health benefits of a lectin-free diet, there are lots of studies on the health benefits of the Mediterranean diet, which includes many foods that are high in lectins, including tomatoes, eggplants, and peppers.

Corn – including foods containing corn and meat from animals feed corn. I put corn and corn products on my ‘avoid’ list but not because of the lectins; rather because most of the corn in North America is genetically modified – plus corn is very starchy/high in sugar. The flesh (meat) of animals fed corn has a very different (and not in a good way) nutrient profile than that of animals who are pastured.

In my opinion, avoiding lectin-containing foods could mean that you’ll also be missing out on the numerous health-boosting nutrients those foods contain. Instead of focusing on avoiding lectin-containing foods, focus on variety and moderation, avoid genetically modified foods, buy pastured animal products, and make sure you properly prepare/cook your grains and legumes. Remember – the detrimental effects of lectins seem to be more likely when the foods containing them are consumed ‘raw’ and at high concentrations, which isn’t typically how they are consumed by most individuals.

Lectin-Free Diet Claims

Lectin-free diets claim to address numerous health issues including:

  • digestive issues such as nausea, diarrhea, bloating, leaky gut, and food intolerances
  • autoimmune disorders (e.g. rheumatoid arthritis, thyroid diseases, lupus, etc)
  • immune insufficiencies
  • joint pain
  • fatigue
  • skin conditions

… however; these health issues seem to be related to pre-existing issues, such as compromised gut health and/or immune function and not strictly related to eating foods that contain lectins.

Lectin-Free Diet: Fact or Fiction

A key point to keep in mind is that lectin-containing foods are typically prepared in a way that neutralizes the potential negative effects of lectins (e.g. removing the seeds from squash, soaking and stewing/cooking beans, etc). In general, I’m not a fan of diets that claim to address virtually every health issue you can think of, especially when there isn’t much properly conducted research backing them up – which is the case with a lectin-free diet.

Ironically, much of the research on lectin-containing foods such as beans and lentils for example, show that they support cardiovascular health, reduce inflammation, and help regulate blood sugar levels due to their high fibre content and low glycemic index/load.

If you have digestive issues, or other health concerns, rather than eliminate all lectin-containing foods from your diet, consult a nutritionist (like yours truly!) for a better approach. The scientific evidence does not support the view that lectins are harmful to our health. What is harmful to our health is promoting a theory that may create fear and stress around eat health-promoting foods.

A Few References



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