Are Lectins Damaging Your Gut?
How bad are they? Are they actually the root cause of all illness? Should we be avoiding plants?
With the rise in interest in the field of nutrition and the popularity of nutrition books, podcasts and social media accounts it is so hard to know what is true when it comes to nutrition advice. So what is the deal with lectins? Are they the root cause of illness?
Now for my regular readers and followers you will hopefully have some alarm bells sounding when you hear the words ‘root cause of all illness’ because I regularly talk about how there is no one cause, there is no one demon we can blame for all ailments. For today though, let’s dive into lectins.
To lay it out on the table the biggest problem I have with the notion we should avoid lectins, is that it is steering people AWAY from eating plants and a plant based diet. I don’t know how many times I’ve said it but plant based eating is king. (FYI plant based doesn’t mean vegan, just mostly plant based.)
What are lectins?
Lectins are a type of protein that bind to carbohydrates, nearly all foods contain lectins in varying levels. Lectins are a defence mechanism for the plant to protect it from pests, and as humans we are unable to digest them.
In small amounts lectins have actually been shown to have some health benefits in their role in the immune system and cell growth with anti-cancer properties. High intakes of lectins on the other hand can hinder the absorption of certain vitamins and can damage the lining of the intestines.
The problem?
As with everything the dose dictates the poison. Let’s take a look at water, can we all agree water is a healthy thing to consume? I would hope so, it is essential to life. However, drop 10L water in the space of a few hours and you’ll soon be dropping dead. Anything can become dangerous when the dose exceeds normal limits.
The same applies with lectins. It all comes down to dosage. So rather than fuss over eliminating all lectins (seriously we would have no foods left to consume) let’s look at what foods are high in lectins and how we can reduce our intake of lectins.
Where do we find lectins?
Firstly, there are different types of lectins, some more harmful than others. Lectins are found in legumes, beans, wholegrain and some vegetables like tomatoes, eggplants and potatoes. There is no evidence however that the lectins found in the vegetables are harmful. The lectins found in wholegrains and legumes can be harmful in high doses though. Keep reading though, don’t stop here… Eliminating legumes and wholegrains is not the answer.
How much is too much?
Legumes and wholegrains contain the highest levels of lectins, but does this mean we need to eliminate them? Surprisingly not, we can actually bring the lectin levels of wholegrains and lectins back down to incredibly safe levels by simply cooking them.
Let's look at kidney beans as an example, when we cook kidney beans we can reduce the levels of lectins from around 40,000 to 400. That is a huge reduction, bringing them back to safe levels.
The Verdict?
We also have strong scientific evidence that eating a diet rich in plants, especially legumes is beneficial for cardiovascular health, cancer risk, weight management and the gut microbiome. Eliminating legumes on the basis of lectins being harmful is not supported. Studies completed in this field often are conducted in animals or cells, not humans and with isolated lectins, not as we find them in foods. There is currently insufficient evidence to recommend avoiding all legumes and grains on the grounds of avoiding lectins.
In my opinion there are many more things we can be focusing on to improve our health, reducing processed foods and a meat heavy diet in place of a plant based diet which includes legumes will likely have a dramatic and positive influence on your health.
What can we do if we are concerned about lectins?
Cook - High temperature cooking, like boiling destroys the lectins. Boiling tends to be more effective at destroying lectins than dry heat like roasting. High lectin foods like wholegrains and legumes should be cooked and more often than not we do cook them, when was the last time you ate raw brown rice?
Fermentation - the fermentation process can break down the lectins making them easier for us to digest. Tempeh is a great example of a fermented legume.
Soaking and Sprouting - Allowing grains and legumes to soak or sprout can also break down the lectins
References:
Grant G, More LJ, McKenzie NH, Pusztai A. The effect of heating on the haemagglutinating activity and nutritional properties of bean (Phaseolus vulgaris) seeds. J Sci Food Agric. 1982 Dec;33(12):1324-6. Citation available from: https://www.ncbi.nlm.nih.gov/pubmed/7166934
Nciri N, Cho N, El Mhamdi F, Ben Ismail H, Ben Mansour A, Sassi FH, et al. Toxicity assessment of common beans (Phaseolus vulgaris L.) widely consumed by Tunisian Population. J Med Food. 2015 Sep;18(9):1049-64. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/26355953
Pedrosa MM, Cuadrado C, Burbano C, Muzquiz M, Cabellos B, Olmedilla-Alonso B, et al. Effects of industrial canning on the proximate composition, bioactive compoundscontents and nutritional profile of two Spanish common dry beans (Phaseolus vulgaris L.). Food Chem. 2015 Jan 1;166:68-75. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/25053030
Mollard RC, Luhovyy BL, Panahi S, Nunez M, Hanley A, Anderson GH. Regular consumption of pulses for 8 weeks reduces metabolic syndrome risk factors in overweight and obese adults. Br J Nutr. 2012 Aug;108 Suppl 1:S111-22. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/22916807
Hermsdorff HH, Zulet MÁ, Abete I, Martínez JA. A legume-based hypocaloric diet reduces proinflammatory status and improves metabolic features in overweight/obese subjects. Eur J Nutr. 2011 Feb;50(1):61-9. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/20499072