If you’ve heard worrying rumours about beans, lentils and other lectin-rich foods, you might be wondering if you need to rethink your diet. Nutrition scientist Tim Crowe puts anti-lectin claims to the test.
Lectins are a recent dietary bogeyman on the block. Condemned by some popular diet books, particularly The Plant Paradox by former heart surgeon Dr Steven Gundry, 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. But what does the science say?
What are lectins?
Lectins are a type of protein. They are produced in the human body and serve as an important part of our immune defence. In plants, they form part of the defence system against predators, and are found in a wide variety of plant foods including legumes (such as beans and lentils), whole grains, fruits and vegetables such as tomatoes and eggplants.
Lectins in our body
The properties of lectins that help plants defend themselves may cause problems for humans during digestion. A good example is the risk of severe reaction to eating raw kidney beans. Kidney beans contain a type of lectin called phytohaemagglutinin, which can make red blood cells to clump together and cause nausea, vomiting, stomach upset and diarrhoea. But there’s a simple solution – cook them. And that’s worth the effort because they have one of the highest antioxidant levels of any food.
Absorbing nutrients
In animal and cell studies, there is some research to show that active lectins (ones that haven’t been neutralised by cooking) can reduce the absorption of some minerals such as calcium, iron, phosphorus and zinc. But this effect is minimal and unlikely to cause nutrient deficiencies in people consuming a varied diet. Many lectin-containing foods are rich in essential nutrients. This makes them an important part of a healthy diet. For instance, legumes are an excellent source of plant-based protein, fibre, and various vitamins and minerals, while whole grains provide essential nutrients like B-group vitamins, magnesium and selenium. Lectins have also been shown to have anti-cancer, anti-microbial, anti-viral and immune-enhancing properties, and have the potential to lower blood sugar in diabetes. What this all means is that the health benefits of consuming foods that contain lectins far outweigh any potential harm.
Lectins & your gut
It is true though that some people – especially people with irritable bowel syndrome (IBS) – may not tolerate lectin[1]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 such as FODMAPs. But most people tolerate lectin-containing foods very well and because of that, our gut loves us for it. High-lectin foods contain loads of prebiotic fibre to feed your gut bacteria. One quick disclaimer here though, is 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 people with coeliac disease to exclude all the other plant foods that contain lectins.
No, lectins are not inflammatory
Because lectins can bind to cells for long periods, they could potentially cause an autoimmune response in some people. That has led to the theory lectins could play a role in inflammatory conditions like rheumatoid arthritis and type 1 diabetes. But there isn’t a lot of human research to support this theory. In fact, human studies have shown that consuming lectin-containing foods, such as legumes and whole grains, is linked to reduced inflammation and a lower risk of chronic diseases.
Are lectins responsible for weight gain?
High-lectin foods are actually 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 frequently in the Western diet.
Practical tips:
Lectins could be a problem for some people. But these cases are rare. That’s because lectins are most potent in their raw state, and the foods containing them are not usually eaten raw. So here are some tips on reducing lectins in foods. 1Cooking foods at high temperatures can help reduce lectin content. Boiling, steaming, and pressure cooking are effective methods for reducing lectins in legumes, grains and other lectin-rich foods. 2Soaking legumes, grains, and seeds overnight before cooking can help reduce lectin levels. Discard the soaking water and rinse thoroughly before cooking. 3Removing the skin and seeds of fruits and vegetables can help reduce lectin intake if it’s a concern for you. 4Fermenting foods can break down lectins and make them more digestible. Examples include fermented vegetables like sauerkraut and kimchi, as well as fermented soy products like tempeh and miso.
The bottom line:
The claims made 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 around, the lectin-free diet, heavily championed by The Plant Paradox, is unnecessarily restrictive and 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.
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