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Evidence Based

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Are Lectins Bad For You? A Clinician’s Perspective

Written by Dr. Michael Ruscio, DC on July 22, 2025

Written by Dr. Michael Ruscio, DC on July 22, 2025 — Reviewed by Hilary Watts

• What Are Lectins?|
• High Lectin Foods|
• Are Lectins Bad for You?|
• Low-Lectin Diet|

Lectins have been in the spotlight, mostly due to media hype and trendy diet books. They’ve been blamed for problems like unwanted weight gain, chronic inflammation, and even autoimmune diseases. But are these claims true? 

As with most topics in the world of nutrition, context is key. Allow me to share what the research says about dietary lectins, so you can make the most informed decision about whether to include them in your diet or not.  

Key Takeaway: Some sources claim that lectins are bad for you. Research shows that high-lectin foods are safe and even beneficial—when they’ve been cooked properly 1.

What Are Lectins?

Lectins are a type of protein that bind to specific sugars (carbohydrates). Lectins are found in all living things, including 2: 

• Grains
• Fruits
• Vegetables (especially beans and legumes)
• Meat
• Fish

In nature, lectins primarily protect plants from predators like insects or animals. Lectins attach to carbohydrates on cell surfaces and digestive enzymes, potentially disrupting digestion or nutrient absorption when consumed, which serves as an effective defense mechanism 3.

Lectins can clump cells together (a process called agglutination) and are grouped based on the type of sugar to which they bind the best 3. For example, phytohemagglutinin is a lectin often found in red kidney beans and white beans. 

Foods High in Lectins

Many foods contain lectins, but some have higher amounts than others.  

The following table describes the lectin content in raw foods from highest to lowest by food group 1 2 4:

As you can see, you would never eat many of these foods in their raw forms. And even those we would eat raw, like hemp seeds, berries, or chia seeds, have naturally lower levels of lectins. 

Are Lectins Bad for You?

As I mentioned earlier, plant lectins have gotten some negative attention, mostly due to a diet program called the Plant Paradox. 

The developer of this diet claims that foods with the most lectins can cause harm and increase the risk of leaky gut in people. The Plant Paradox diet eliminates plant-based foods such as legumes, nightshade vegetables, and grains, as well as dairy products. This diet claims to help with weight loss and recovery from various health conditions, like rheumatoid arthritis. 

Now, it’s true that eating high amounts of raw or undercooked bean lectins can cause digestive problems like nausea, vomiting, bloating, and diarrhea in humans. This has been documented in several countries, including the UK, Japan, China, and Denmark, usually in people who ate raw or undercooked red kidney beans or green beans 2. 

Additionally, some types of lectins (like ricin from castor beans) are extremely toxic—just tiny amounts can be fatal 5. And animal studies show that high lectin intake (at doses far beyond what a human would eat) has been linked to gut tissue damage and slowed growth 1.

Some healthcare professionals even call lectins “anti-nutrients” because of animal studies showing they can negatively impact digestion, gut health, and immune function 5. 

However, most of this thinking about lectins is based on older cell and animal studies that highlighted their toxic effects, especially when eaten raw or in large amounts 5. 

Current human research does not support the notion that lectin-rich foods are harmful when they’ve been cooked properly. Thoroughly cooking lectin-rich foods, like legumes, eliminates lectins. 

Furthermore, multiple high-quality studies have shown that foods with higher amounts of lectins, like legumes, potatoes, tomatoes, and whole grains, have beneficial health effects. 

Here are some highlights from human trials:

• Whole grains may lower type 2 diabetes risk and improve blood sugar markers 6, and protect against heart disease 7. Choosing a wide variety of whole grains and eating more than 150 grams (about 1.25 cups) per day may be best 6. 
• Beans (navy, pinto, or red) show potential health benefits for heart health, cancer, diabetes, and obesity, although more research is needed 8. 
• Tomatoes may protect against death from cardiovascular disease, cerebrovascular disease, and all causes, and against prostate cancer and gastric cancer 9.  
• Legumes (like beans, lentils, and peas) may protect against death from stroke and all causes 10, and against heart disease 11.
• Potatoes, when compared to refined grains, may have gut microbiome benefits 12. 

The majority of human research suggests that foods high in lectins aren’t simply bad for us—they likely have health benefits. But context is key. Raw or undercooked forms of high-lectin foods (especially dried beans, lentils, and peanuts) can cause serious digestive issues and lectin toxicity 1 2. 

Cooking to Deactivate Lectins

Although there’s still some debate about how to cook lectin-rich foods to ensure their lectins aren’t harmful, a food study found the following soaking and/or boiling times to effectively deactivate lectins 2: 

Another food study found that roasting raw peanuts for 30 minutes deactivated 100% of their lectins 13.

If you’re cooking raw beans or lentils, stick with pressure cooking, soaking before cooking, or boiling to deactivate the lectins. There’s no need to worry about soaking and boiling canned foods high in lectins (like beans and lentils) and roasted peanuts because they’ve already been cooked properly. 

I know you’re probably thinking: What about raw tomatoes and bell peppers? So far, human research has not shown any negative impact. 

The bottom line is: Getting a little bit of lectins here and there isn’t going to be a problem, and future research may even prove it’s beneficial. 

What Is a Low-Lectin Diet, and Is It Right for Me?

There’s very little scientific evidence that a low-lectin diet is necessary. However, if you struggle with gut symptoms, temporarily eliminating some lectin-containing foods may be helpful for you. 

Many of my clients in the clinic report feeling better when they avoid beans, legumes, nightshades, and grains. In my experience, it’s not the lectin content but rather the high FODMAP content of these foods that causes negative symptoms. 

And this isn’t just my opinion, it’s supported by research—eating high-FODMAP foods has been associated with increased gas production and gastrointestinal symptoms in people with irritable bowel syndrome (IBS) 14. 

FODMAPs are Fermentable Oligosaccharides, Disaccharides, Monosaccharides, And Polyols—fancy words for different types of fermentable starches and sugars in certain foods. 

A low FODMAP diet is perhaps the most effective diet for improving IBS symptoms 15. It likely works by reducing gut water and gas in sensitive individuals, changing the gut microbiome, and affecting immune and gut barrier functions 16. It might also starve bacterial overgrowths that may cause IBS symptoms, gut inflammation, and leaky gut 17 18. 

Outside of IBS, we’ve seen benefits at the clinic when using a low FODMAP diet for many conditions, including:

• Inflammatory bowel disease with IBS symptoms
• General GI symptoms (abdominal bloating and pain, diarrhea, constipation, and gas)
• Leaky gut
• Gut inflammation
• Gut dysbiosis
• Fibromyalgia pain
• Anxiety

So, rather than eating a low-lectin diet, we often recommend trying a low FODMAP diet for several weeks to months. During the elimination phase of the diet, we’re taking the pressure off the digestive system, restoring balance to the gut microbiome, and allowing the gut to heal. 

Once symptoms are calm, we systematically reintroduce high-FODMAP foods to determine each individual’s tolerance to a broad array of nutritious foods. The majority of the time, our clients find they can come to enjoy a wide variety of whole foods (even those high in lectins and FODMAPs) without gut symptoms.

Lectin-Rich Foods Are Safe When Properly Cooked

Lectins are proteins that can bind to sugars in food. No one knows exactly what they do in the human body, but we do know eating raw and undercooked lectins can cause digestive distress and lectin toxicity.

However, food studies show that proper cooking deactivates most lectins. And, high-quality human research suggests that high-lectin foods are generally associated with good health, and they can be part of a balanced diet.

If you enjoy and tolerate eating high-lectin foods, there’s no need to stop (as long as you’re cooking them properly). If you notice digestive symptoms when you eat foods with a high lectin content, lectins may not be the root cause. Lectin-containing foods like legumes are also high in FODMAPs—potential gut irritants. 

A trial of a low FODMAP diet along with other natural gut-healing therapies can help restore great gut health and get you back to eating the lectin- and FODMAP-rich foods you love. 

If you’d like a more personalized gut-healing plan, contact us at the Ruscio Institute for Functional Health for an appointment with one of our experienced clinicians.

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