Are Lectins Bad for You? Food Guide

Can eggplant, tomatoes and beans really be bad for you? It depends upon whom you ask.

In recent years, dietary lectins (found in certain types of plant-based foods) have been villainized as a cause for various adverse health effects, thanks to the popularity of a book called The Plant Paradox by Dr. Steven Gundry. In his book, Dr. Gundry credits overconsumption of plant lectins for a host of chronic diseases and conditions, such as chronic inflammation, heart disease, leaky gut syndrome, weight gain and autoimmune diseases like rheumatoid arthritis and celiac disease.

In turn, according to Dr. Gundry, a lectin-free diet is aimed to promote weight loss, provide immune system support and improve gut health.

Here is everything you need to know about lectins, including their potential health benefits and drawbacks, a list of lectin-rich foods and how to follow a lectin-free diet.

What are lectins and what do they do?

Lectins, also known as “hemagglutinins,” are a family of carbohydrate-binding proteins found in all plant-based foods, but at especially high levels in certain vegetables, raw beans and grains. Of those carbohydrates, lectins have a high sugar-binding affinity for N-acetylgalactosamine, N-acetylglucosamine and N-acetylneuraminic.

Lectins can cause a range of effects in the body, including “agglutination” or clumping of red blood cells, GI upset and chronic inflammation from long-term binding of cells in the digestive tract. They can also cause interference of nutrient absorption—including calcium, iron and zinc—because of their antinutritional properties.

That being said, not all lectins affect the body in the same way. In fact, some play important biological roles.

Which foods are high in lectins?

Various types of plant foods have a high lectin content, including:

• Nightshade vegetables (tomatoes, peppers, eggplant)
• Legumes including soybeans and red kidney beans
• Grain-fed and conventionally-raised animal proteins as opposed to pasture-raised and grass-fed protein
• Gluten-containing whole grains like wheat
• Pseudo-grains like quinoa

Do all lectins affect your body the same way?

While some lectins may cause physiological harm, early research is looking at the potential therapeutic properties of certain lectins in anti-cancer treatments due to their ability to cause cancer cell death.

Additionally, a meta-analysis in large populations have found associations between consumption of foods high in lectin content—such as legumes, nuts and whole grains—with health benefits including weight loss support and lower rates of cardiovascular disease and type 2 diabetes.

Which lectins are good for you?

Despite the concerns, lectin-rich foods are considered healthy in many ways. The lectins in tomatoes and nuts provide health benefits by acting as antioxidants to protect against oxidative damage. They also help slow down digestion and carbohydrate absorption, which can help prevent sharp rises in blood sugar and insulin.

Which lectins to avoid?

According to research, the problematic compounds in foods high in lectins are the phytohaemagglutinins, which are found abundantly in some legumes such as undercooked or raw kidney beans. Studies suggest that in excess, they can bind to red blood cells and cause them to clump together. Additionally, they can cause nausea, vomiting, stomach upset and diarrhea in some people. This is why properly preparing kidney beans, lentils and other legumes is so important.

Wheat germ agglutinin (WGA) is a resistant lectin that can survive the cooking process. This lectin is found primarily in wheat-based products, albeit in low concentrations. It is important to note that to date, there have been no controlled clinical trials assessing the health effects of WGA. The majority of the data still shows favorable health effects from consumption of whole grain and cereal products.

In The Plant Paradox, Dr. Gundry encourages following a lectin-free diet to reduce heart disease risk, prevent weight gain, support weight loss, and reduce unwanted symptoms of leaky gut, inflammatory bowel disease and autoimmune disease.

How to remove lectins from food?

Cooking can help to reduce lectin activity. For example, boiling lectin-filled legumes for one hour at 95 degrees Celsius (203 degrees Fahrenheit) has been found to reduce lectin-related activity by 94-99%, and adequate boiling of kidney beans results in elimination of harmful lectins. The process of soaking can also help reduce lectins in high-lectin foods. It is important to note is that both high-heat cooking and soaking will remove some of the water-soluble nutrients along with the antinutrients.

Additionally, pressure-cooking legumes and other foods high in lectin content can be an effective way to reduce the high amounts of harmful lectins and anti-nutritional effects.

What is a lectin-free diet?

According to Dr. Gundry in The Plant Paradox, a lectin-free diet avoids grains, legumes, and the seeds and skins of many fruits and vegetables.

This sample day of eating limits high plant lectin foods. Avoiding lectin-rich foods doesn’t mean you can’t still follow a nutrient-dense diet that helps to manage inflammation. While many lectin-rich plant foods also provide high amounts of nutrients, including protein and fiber, there are many lectin-free foods to choose from that are nutritionally suitable swaps.

Sample day of eating:

• Breakfast: Green smoothie made with ½ avocado, ½ juiced lemon, 1 cup of romaine lettuce, 1 cup of spinach, 1 cup of water and ¼ cup of ice.
• Snack: 1 oz. of extra dark chocolate with ¼ cup of raw walnuts
• Lunch: Tuna avocado salad romaine boats made with 1 can of wild-caught tuna in water mixed with 1 mashed avocado, 1 diced celery spear, ¼ cup of diced red onion, 1 tbsp of avocado oil and salt and pepper to taste served out of romaine lettuce boats.
• Dinner: Fall sheet pan (recipe below).

Fall Sheet Pan Recipe

Serves: 2
Prep time: 10 minutes
Cook time: 20 minutes
Total time: 30 minutes

Ingredients:

1 bag of frozen cauliflower gnocchi
1 medium parsnip, peeled and cut into 1-inch pieces
1 cup Brussels sprouts, ends trimmed and halved
1 medium sweet potato, cut into 1-inch pieces
2 tbsp extra virgin olive oil
¼ cup fresh basil, chopped
1/2 medium red onion, thinly sliced
½ tsp sea salt
½ tsp pepper
¼ cup crumbled goat milk cheese (optional)

Directions:

1. Preheat the oven to 450 degrees Fahrenheit and line a sheet pan with parchment paper.
2. Toss gnocchi, parsnips, brussels sprouts, sweet potato, onion, oil, salt and pepper in a large mixing bowl until well combined and spread mixture evenly on the prepared sheet.
3. Roast for 20 minutes, tossing halfway through until the vegetables are tender and slightly crisp, and the gnocchi begins to plump.
4. Serve with fresh basil and crumbled goat cheese, if desired.

Foods to avoid if you’re eating a lectin-free diet

Here is a partial list of foods with a high level of lectins that should be avoided on a lectin-free diet. You’ll note that many of these are well-known for their health benefits…which is why you should be certain that you need to avoid lectins before banning them from your kitchen!

• Eggplant
• Tomatoes
• Bell peppers
• Vegetable oils
• Raw red kidney beans
• Raw lentils
• Raw peas
• Raw soybeans
• Peanuts
• Cashews
• Corn
• A1 beta-casein protein dairy products, like most cow’s milk and cheeses
• Wheat
• Quinoa
• Grain-fed and conventionally-raised animal protein
• Pumpkin seeds
• Sunflower seeds
• Potatoes
• Pasta
• Pumpkin
• Zucchini
• Soy sauce

Who should avoid lectins?

Most healthy individuals have innate defense mechanisms that can help manage their response to lectin exposure. High lectin foods and carbohydrates prepared properly—pressure-cooked or soaked overnight and boiled—can also limit your exposure to antinutrients. However, those with inflammatory bowel issues may need to avoid certain lectins, and lectins may elicit an overactive immune response in select individuals.

How do you test for lectin allergies?

Since avoiding lectins could be closing the door to a number of healthy and delicious foods, you should work with a doctor to confirm that a lectin-free diet is the right choice for you.

Tests for food allergies can be done using a skin prick test or by measuring levels of immunoglobulin E (IgE), an antibody that contributes to an allergy-related immune response. The gold standard for food allergy diagnosis is an oral food test. Work with your allergist to set up this test, which can be time consuming and dangerous if not done under a physician’s care.

References

• Ghanbari-Gohari, Faezeh et al. “Consumption of whole grains and risk of type 2 diabetes: A comprehensive systematic review and dose-response meta-analysis of prospective cohort studies.” Food Sci Nutr., March 2022, https://pubmed.ncbi.nlm.nih.gov/35702290/
• Petroski, Weston et al. “Is There Such a Thing as “Anti-Nutrients”? A Narrative Review of Perceived Problematic Plant Compounds.” Nutrients, September 2020, https://www.mdpi.com/2072-6643/12/10/2929/htm
• Torigoe, Shota et al. “Immune discrimination of the environmental spectrum through C-type lectin receptors.” Int Immunol., November 2021, https://pubmed.ncbi.nlm.nih.gov/34599808/
• “Evaluation, testing and diagnosis for food allergies.” University of Michigan Health, https://www.uofmhealth.org/conditions-treatments/food-allergy/diagnosis-testing    
• “Lectins.” Harvard T.H. Chan School of Public Health, https://www.hsph.harvard.edu/nutritionsource/anti-nutrients/lectins/
• “Reducing Gluten and Lectins to Calm Autoimmune Symptoms.” Autoimmune Association, https://autoimmune.org/reducing-gluten-lectins/