The lectin lowdown: time to counter the fear campaign about these plant proteins

In recent years, there has been a surge of interest in the potential negative health effects of lectins. What are lectins? They’re a type of protein found in many plant foods such as legumes, wholegrains and some fruits and vegetables. If you take YouTube clips and popular diet books on their word, then these lectins are harmful to human health and are a major driver of inflammation, weight gain and many chronic diseases. Of course, to believe all this, you need to suspend the reality that humans have been eating these foods for thousands of years and it is only in modern times that we have been hit with all these major health problems. But hey, we need to blame it all on something I guess and lectins seem like a great way to sell books and get website clicks. In this podcast, I’ll explore the role of lectins in the diet, the alleged health risks, and counter that with the health benefits of eating lectin-containing foods.

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Transcript

In recent years, there has been a surge of interest in the potential negative health effects of lectins. What are lectins? They’re a type of protein found in many plant foods such as legumes, wholegrains and some fruits and vegetables. If you take YouTube clips and popular diet books on their word, then these lectins are harmful to human health and are a major driver of inflammation, weight gain and many chronic diseases. Of course, to believe all this, you need to suspend the reality that humans have been eating these foods for thousands of years and it is only in modern times that we have been hit with all these major health problems. But hey, we need to blame it all on something I guess and lectins seem like a great way to sell books and get website clicks. In this podcast, I’ll explore the role of lectins in the diet, the alleged health risks, and counter that with the health benefits of eating lectin-containing foods.

Lectins. They’re the new dietary demon on the block that has some people positively apoplectic in their concern for them allegedly causing us all manner of health harms. Pushed by popular diet books, one in particular called The Plant Paradox by one Dr Steven Gundry who is a former heart surgeon, these lectins are supposedly a major cause of obesity, chronic inflammation, autoimmune diseases, cancer and heart disease as well as a shopping list of other problems such as acne, bloating, joint pain, migraines and fatigue. Oh my.

So what are lectins? Lectins are a type of protein found in many plants. We also have them naturally inside of us as they serve as an important part of our immune defence. In plants, lectins form part of its defence system against predators. Lectins are found in a wide variety of plant-based foods, including legumes (such as beans, soybeans, lentils, kidney beans and peanuts), wholegrains, and some fruits and some vegetables such as tomatoes, potatoes, and eggplants. That’s a lot of traditional foods in diets eaten around the world that contain lectins – how on earth has humanity survived this long with all these ‘toxic disease-causing substances in our diet! Yes, I was being sarcastic. In fact, the healthiest populations in the world, known as the Blue Zones, eat more lectin-containing foods than anyone else. Go figure.

Lectins are capable of binding to sugar molecules, allowing them to interact with other proteins, cells, and carbohydrates. The same properties of lectins that make them a handy way for plants to defend themselves in nature may cause problems for us humans during digestion. Which, I will add straight away has some truth to it. The most well-described accounts refer to severe reactions in people eating raw kidney beans. Kidney beans contain a type of lectin called phytohaemagglutinin which can cause red blood cells to clump together. It can produce nausea, vomiting, stomach upset, and diarrhoea. But did you pick up that I said uncooked red kidney beans? Hands up who eats their kidney beans raw? No one. If you cook them, then lectins be gone. Simple.

But from cases like these that have some truth to them, it helps serve the agenda of people who need website traffic and clicks to sell their scary messages, diet books and supplements who can then build an incredibly selective and biased case of just one food component explaining many of today’s modern health ills. Here’s one thing those people won’t be telling you about those red kidney beans I just talked about: they are the food with one of the highest levels of antioxidants measured. You can see already the issue that you run into by demonising a food or group of foods, in this case, legumes, because you want to scare the pants off everyone to do with one component of that food and ignore all the health benefits of other components of it.

Now at least in animal and cell studies, there is some research to show that active lectins (that is ones that haven’t been neutralised by cooking foods) can reduce the absorption of some minerals, especially calcium, iron, phosphorus, and zinc. While it is true that lectins can bind to these minerals and reduce their absorption, this effect is minimal and unlikely to cause nutrient deficiencies in people consuming a balanced diet. And if you spent your life worrying about what nutrients in your diet could potentially impair absorption of other nutrients then you would starve to death because most nutrients interact to an extent to either improve or retard absorption of other nutrients. Eat a varied diet and you can hit the snooze alarm on needing to know much more about this. And to counter this, many lectin-containing foods are also rich in essential nutrients, making them an important part of a healthy diet. For example, legumes are an excellent source of plant-based protein, fibre, and various vitamins and minerals, while wholegrains provide essential nutrients like B-group vitamins, magnesium, and selenium.

It is true though that some people – especially people with IBS – may not tolerate lectin-containing foods so well, though here it is hard to disentangle the effects of other components of foods high in lectins that are also linked to IBS and I’m looking at you FODMAPs. But most people do tolerate lectin-containing foods very well and because of that, our gut loves us for it because those same high-lectin foods contain loads of primo prebiotic fibre to feed our gut bacteria. But I should mention here that gluten is a lectin and there is no debate about the need for people with coeliac disease to exclude this from their diet. But there is no need for them to exclude all the other plant foods that contain lectins.

And at least in theory, because lectins can bind to cells for long periods of time, they could potentially cause an autoimmune response in some people. So some people theorise they could play a role in inflammatory conditions like rheumatoid arthritis and type 1 diabetes. Note I used the word ‘theorise’, as there isn’t a lot of human research to support this or at least blame lectins as the smoking gun. In fact, many, many human studies, to the level that you can do meta-analyses on them, have shown that consuming lectin-containing foods, such as legumes and wholegrains, is linked to reduced inflammation and a lower risk of chronic diseases. Theories, like dreams, are free but they’re a great way to sell fad diet books.

But wait, you’ll find plenty of people attesting to the benefit of going on a popular lectin-free diet, especially for helping with weight loss. The claim here is that lectins can contribute to weight gain by promoting fat storage and increasing appetite. But dig deeper into the food recommendations on such diets and you’ll see it’s just smoke and mirrors for a low-calorie, low-carbohydrate diet – no grains, no legumes, very little fruit, and no tomatoes, potatoes, eggplant and bell peppers. That’s a lot of food rules you need to follow so it is hardly a surprise that people can lose weight following it and with weight loss can come an improvement in some metabolic markers such as inflammation. But it has nothing to do with you having fewer lectins in your diet – you’ve just been conned into following a low-calorie diet that’s all. And those same high-lectin foods that you are told to cut out such as wholegrains and legumes are linked to positive weight management and metabolic health – if anything, you want more of these foods in your diet in place of the typical highly processed foods that feature too commonly in the Western diet.

While the claims about the dangers of lectins are largely unfounded, there is ample evidence to support the health benefits of consuming lectin-containing foods. Legumes and wholegrains have been associated with a reduced risk of chronic diseases, positive weight management, and improved metabolic health. Additionally, many lectin-containing foods are rich in dietary fibre, which has been shown to promote digestive health, lower cholesterol levels, and reduce the risk of heart disease. Foods containing lectins are rich sources of B-group vitamins, protein, fibre and many minerals. Thus, the health benefits of consuming these foods far outweigh the potential harm of lectins in these foods.

Practical tips

Throughout this podcast, I have noted that lectins could still be a problem for some people, but these cases are rare. One reason is that lectins are most potent in their raw state, and the foods containing them are not typically eaten raw. One example is dried beans. To prepare them for eating, they are soaked for several hours and then boiled for several more hours to soften the bean, which denatures the lectins. Canned beans are cooked and packaged in liquid, so they are also low in lectins.

So, let’s wrap all this up. The claims about the dangers of lectins in food are largely unfounded, exaggerated and not supported by the current body of scientific evidence. Of all the fad diets that are around, the lectin-free diet, heavily championed by one Dr Steven Gundry in his book The Plant Paradox is one of the worst you could follow. It fills your head with nutritional science nonsense and puts you on a restrictive diet that kills the joy of eating many foods, all the while emptying your plate of some of the most healthy and beneficial foods you could be eating.

So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.

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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.