The Latest on Lectins

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Lectins have become a buzzword in nutrition circles over the past few years. In some camps, lectins are seen as the enemy. The theory is that they trigger inflammation and intestinal permeability, contributing to chronic disease.

Those who follow this doctrine avoid legumes and grains, two categories of foods with high levels of lectins. However, it’s worthwhile to consider that many traditional cultures consumed diets based on grains and legumes yet did not suffer from the chronic conditions in the numbers we see today. So, are lectins really as bad as their tainted reputation makes them out to be? Or, are there other factors that contribute to inflammatory conditions? Let’s look at what the literature has to say.

What are Lectins?

Lectins are a category of proteins that reversibly bind to carbohydrates. These properties lead to their involvement in many activities, such as cell recognition, inflammation, host defense, cell development, and tumor metastasis. Although lectins are often discussed in conversations about the potential health benefits or problems of grains and legumes, you can actually find lectins in a number of species, including humans, animals, plants, and microorganisms.

Plant lectins are commonly found in fruits, vegetables, nuts, and as I mentioned, grains and legumes. In plants, lectins often act as part of the defense system. 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.

Newer research would suggest that lectins exert antibacterial, antifungal, and antiviral activity, and certain types have been studied for novel biomedical uses against viruses such as SARS-CoV-2 virus, influenza virus, HIV-1, herpes virus, and more, although more definitive studies are needed. Researchers are studying their utility as an insecticide for agriculture, which could be an alternative to current chemical insecticides.

What Makes Lectins Problematic?

Many in the nutrition and wellness field have placed lectins into a category known as “anti-nutrients.” As the name suggests, this description means they actively take away from health and nutrition. Lectins are postulated to cause inflammation, intestinal permeability, and increased risk of food allergy and intolerance. Plant lectins have been found to be more resistant to heat than animal proteins, so there is concern that their anti-nutrient properties persist even if they are not eaten raw.

Are Lectins Really Inflammatory?

There have been some studies demonstrating that lectins trigger inflammation, which give rise to the theories discussed above. For example, one study found plant lectins produced inflammation by activating the NLRP3 inflammasome in both mouse models and human cells. Studies on wheat germ agglutinin, the lectin found in wheat, point to the potential to cause inflammation through binding to the gut lining, inducing an inflammatory response, and possibly cause intestinal permeability.

However, many of these studies may not accurately portray lectin consumption by humans. Instead, many studies are conducted using animals or cells cultures and look at isolated lectins rather than considering the larger context of a person’s diet. Studies can use raw, non-cooked lectin-containing food. Most people do not consume raw legumes, so a study in which mice consume raw legumes does not accurately portray what happens in the human diet. Additionally, the lectin content in a plant depends on a variety of factors including the stage of growth and cultivation area.

How Can You Reduce the Potential Downsides of Lectins?

Some people may complain of the gastrointestinal effects of lectins such as indigestion, bloating, and gas, although it’s difficult if they are responding specifically to the lectins in isolation. It is worth considering if their gut function is impaired, making it difficult to digest fiber. Alternatively, an individual may be experiencing a food intolerance.

Nevertheless, there are traditional ways in which foods can be prepared in order to greatly diminish the lectin content. The best ways to reduce the potential downsides of lectins include:

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 autoclaving.

Are There Health Benefits to Consuming Lectin-Containing Foods?

There are many beneficial nutrients, including essential vitamins, minerals, antioxidants, phytochemicals, and fiber found in whole grains, legumes, and other lectin-containing foods. Studies have found that consuming whole grains and legumes, or the Mediterranean-style diet, which includes grains and legumes, can be healthy and even control chronic conditions, such as type 2 diabetes.

A systematic review found an inverse association between whole grain intake and all-cause mortality, while legumes have been found to reduce inflammation in diabetics.

On the other side of the discussion, there have been studies that demonstrate the health benefits of a Paleolithic-style diet, which removes many lectin-containing foods such as legumes and whole grains. While the Paleo diet can have beneficial impacts on glucose and insulin levels, a meta-analysis did not find these changes to be significantly different from other dietary patterns, such as the Mediterranean diet. One thing that both diets have in common is that they are rich in whole, unprocessed foods.

Closing Thoughts

What’s the takeaway? When some lectin-containing foods are not prepared properly, they can be toxic and lead to food poisoning and death in certain individuals. In general, though, there is a lack of significant clinical evidence (i.e., human trials with whole foods) directly pointing to the problems that have given lectins a bad reputation, such as inflammation and intestinal permeability. That doesn’t mean lectins might not still be worth avoiding for some people, especially those who are sensitive.

Finally, my premise as a nutrition clinical researcher is that different foods may present us with challenges at some time in our lives. That may be because of the food, or it may be because of our physiology, or both together. It’s essential to be aware of our symptoms and ongoing bodily reactions. As I always say, if you have questions about which foods can best support your health or have questions or concerns about food allergies or lectins, it is best to work with a trained health professional to help you figure out the underlying root cause and guide you on your healing path.

 

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