What’s the scoop on Lectins?

19 May 2020

Lectins have become a focal point in nutrition circles, especially in inflammatory conditions. The anti-lectin diet was popularized by The Plant Paradox, a book written by cardiac surgeon Steven Gundry, MD. In this book, Gundry claims that lectins found in plants can cause weight gain and inflammation.

What are lectins?

Lectins are a type of protein that can bind to cell membranes, as such they offer a way for molecules to stick together. This process is termed Agglutination, comes from the Latin agglutinare (glueing to).

Lectins are ubiquitous in nature and in plants are primarily a defence against microorganisms, pests, and insects. Lectins are abundant in raw legumes, nuts and grains, and most commonly found in the part of the seed that becomes the leaves when the plant sprouts. Like many seeds,  Lectins are resistant to human digestion and they enter the blood unchanged.

Certain lectins are known to be toxic to animals and humans, such as ricin (a lectin toxin from castor beans used as a poison), and hemagglutinin in red kidney beans.  

Immune response to lectins

As previously mentioned, because we don’t digest lectins, our immune system can produce antibodies to them. Almost everyone has antibodies to some dietary lectins in their body but this doesn’t mean that these are “bad” for all.  There does however appear to be a correlation to individuals with Rheumatoid Arthritis, as agglutinating factor is present in the serum of most patients with rheumatoid arthritis and some with other collagen diseases, so we know they have agglutination “issues”, and thus can be prone to lectin issues. 

Studies on wheat germ agglutinin, the lectin found in wheat, suggest there is a potential to cause inflammation through binding to the gut lining, inducing an inflammatory response, and possibly cause intestinal permeability.  

If lectins affect the gut wall in this manner it could also cause a broader immune system response as the body’s defences move in to attack the invaders as a result of intestinal permeability.  Symptoms can include skin rashes, joint pain, and migraine. 

Are there some Lectins everyone should avoid? 

Sprouted Red Kidney beans! - not that I think this would be your go-to picnic favourite! - but it’s due to phytohaemagglutinin – a lectin that can cause red kidney bean poisoning. The poisoning is usually caused by the ingestion of raw, soaked kidney beans. As few as four or five raw beans can trigger symptoms.

Raw kidney beans contain from 20,000 to 70,000 lectin units, while fully cooked beans usually contain between 200 and 400 units.

How Can You Reduce the Potential Downsides of Lectins? 

Some people may complain of gastrointestinal effects of lectins, such as indigestion, bloating, and gas, although it’s difficult to know for sure if they are responding specifically to the lectins in isolation. It could also be that their gut function is impaired and they are not able to process fibre. But, to be proactive, the traditional ways in which people prepare these foods greatly diminish the lectin content to reduce many of the problems. The best ways to reduce the potential downsides of lectins include: 


Soak beans and legumes overnight, and change the water often. Drain and rinse again before cooking. Adding sodium bicarbonate to the soaking water may help neutralise the lectins further.


Sprouting seeds, grains or beans decreases the lectin content. Generally, the longer the duration of sprouting, the more lectins are deactivated. In some cases the lectin activity is enhanced by sprouting (like alfalfa sprouts). The lectins in some grains and beans are in the seed coat. As it germinates, the coat is metabolised – eliminating lectins.

Heating, or Steaming with high pressure

Pressure cooking will reduce the lectins in beans, tomatoes, potatoes, quinoa, and many other foods, but won’t be effective for wheat, rye, barley, spelt or oats. In one study, the levels of PHA (phytohemagglutinin), a toxic lectin found in red kidney beans and other legumes, was completely gone in common beans that underwent soaking and cooking or pressure cooking. Avoid slow cookers for lectin-foods as the low temperature may actually increase some lectin content.  

Interestingly certain seaweeds and mucilaginous vegetables like chia seeds, okra, aloe vera, kelp and figs have the ability to bind lectins in a way that makes them unavailable to the cells of the gut.

Peeling and De-seeding

For many foods, the seeds, skins and rinds are where the majority of the lectins are contained. Therefore, peeling and removing the seeds from foods like cucumbers, peppers, tomatoes and courgette may reduce the lectins sufficiently for you to eat them without suffering negative consequences. This is one of the reasons that white bread and white rice have fewer lectins than whole wheat bread and brown rice.

What are the top lectin foods

Should I avoid?

I would suggest trialling a removal if you have a joint or collagen-based inflammatory condition, but always under the guidance of a healthcare professional. Certainly soaking and steaming at pressure is advised for all with regards legumes and anyone with inflammatory bowel disease could do well to peel and deseed the vegetables stated.

As always, in health

Tanya x