The Truth About Plant Lectins

Larry A. Law

Lectins are proteins that bind to carbohydrates—in short, they are glycoproteins. There are thousands of kinds of lectins and some are blamed today for creating digestive problems, brain fog, and several other health challenges. However, many of the plants containing lectins are among the healthiest foods you could possibly eat. Lectins are in beans, tomatoes, potatoes, lentils, peanuts, soy, peas, fruits, wheat, rice, and barley. So, are they bad for you or not? While lectins don't have any nutritional value by themselves, they occur throughout nature in plants and animals that do provide nutritional value. They are even in bacteria and viruses.
​The primary reason there is controversy about eating lectins today is because of a book written in 2017 by Dr. Steven Gundry titled The Plant Paradox. The book advocates eating a lectin-free diet. He claims that many people suffer from lectin intolerance or sensitivity with symptoms of bloating, gas, nausea, diarrhea, fatigue, aching joints, and allergic reactions. Gundry claims lectins are our biggest dietary danger and may even be killing us. But are the claims backed up by real research? Both Ocean Robbins and I agree that the answer is no. Foods containing lectins are not our enemy and the evidence Gundry claims in his book is flimsy at best.

Foods Containing Lectins Are Not the Enemy

Dr. Gundry is telling people to be afraid of foods like beans, fruits, and vegetables. But those same foods are among the healthiest foods on the planet. The more we eat, the lower our risk of heart disease, cancer, Type 2 diabetes, and Alzheimer's disease. Gundry clearly knows that the foods he villifies provide critical nutrients. Yet his solution is largely synthetic pills and powders. He does promote one good supplement he formulated which he calls a lectin shield. His product actually contains tiny amounts of 3 sugar nutrients (N-acetyl D-glucosamine, D-mannose, and larch arabinogalactan). These sugars are undoubtedly the main reason his product provides any benefit to his consumers. I offered to explain to Dr. Gundry the science of glycobiology and why these sugar nutrients were so powerful in supporting immune system health, but he never took the effort to follow up with me. I concluded from his website that he is more interested in selling supplements and making money. Real education is not his ultimate purpose, but only a ploy used to justify the sale of countless products on his website.

His lectin shield, with minimal amounts of three sugar nutrients, costs $80. But he insists on 10 other supplements that he calls "must-haves." Membership in his VIP discount club will run about $10,000 a year. That membership is really what he is selling with his fear-mongering. If you genuinely want to eliminate lectins, it turns out that you only have to cook them. Even Dr. Gundry admits that when you cook beans, the lectins are rendered completely harmless. All canned beans you buy in the store are pressure-cooked, so they are already very safe and devoid of any possible harmful activity.  

While there may be some people who should avoid lectins (people with allergies to lectin-containing foods or people with digestive sensitivity due to irritable bowel syndrome or Crohn's disease), most people will find tremendous benefit from eating fruits, vegetables, and legumes. There is no real plant paradox. Lectins defend the plant and serve as a type of immune system. But the foods containing lectins have boat-loads of beneficial vitamins, minerals, phytonutrients, and sugar nutrients that are vital for your health. The vast majority of people have no negative reactions to whole food. But if you ever experience mild reactions from eating lectin-containing foods, just soak or cook them to minimize any potential side effects. Following Dr. Gundry's instructions to avoid eating these foods is terrible advice. Chronic disease is clearly linked to eating too many low-nutrient, low-fiber, heavily-processed foods, yet he is warning us to stop eating the healthiest foods on the planet. It doesn't pass the common sense test.  

Goitrogens and Your Thyroid

Another bloated warning making its way around social media concerns goitrogens and their effect on your thyroid. Goitrogens, like lectins, exist in plants—some of the healthiest foods on earth contain them. Plants like cabbage, kale, cauliflower, broccoli, brussels sprouts, turnips, soybeans, lima beans, and even sweet potato are among the highest levels. Goitrogens also exist in pharmaceuticals and in environmental chemicals—polychlorinated and polybrominated biphenyls (PCBs and PBBs). Goitrogens can block the body's uptake of iodine. Too little iodine can lead to hypothyroidism. Of course, synthetic, industrially created goitrogens are a huge problem because they are everywhere. Our question is whether goitrogens in food do the same thing and are equally bad. 

It turns out that excessive consumption of goitrogenic foods may disrupt thyroid function and contribute to the development of hypothyroidism in certain cases. But the amount needed to do this is extremely large and abnormal. A 2015 study of rabbits eating only cruciferous vegetables for a solid month significantly impacted both male and female fertility (no offspring) compared to a group limited to eating cruciferous vegetables two out of every three days for a month (normal offspring). While humans are not rabbits, research strongly shows that eating cruciferous vegatables has many powerful health benefits. The amount of goitrogens consumed in typical serving sizes of cruciferous vegetable is basically insignificant and the health benefits far outweigh this risk. This is especially true if you are getting enough iodine in your diet and you are not already suffering from hypothyroidism.

How to Reduce Goitrogens in Food

Hyperfocusing on any specific food to the exclusion of other foods can cause vitamin and mineral deficiencies, as well as an overdose of compounds like goitrogens. So, vary the food that you eat. Another strategy is to soak goitrogenic foods like beans before cooking them. Soaking can reduce the levels by removing those that are water soluble or by deactivating enzyme inhibitors. Also, steaming and boiling these foods can reduce goitrogens by as much as 80%. Remember that for most people, there is no need to worry about goitrogens in a normal diet, since the levels are not anywhere high enough to cause harm. If you do have thyroid issues, then moderate your consumption of raw goitrogenic foods or make sure to soak, steam, or boil them.