Lectins? - Say what?
No, they have nothing in common with Hannibal Lecter apart from the fact that occasionally they can be a bit evil and may very well make us feel like our guts have been ripped apart!
Sometimes foods get labelled as ‘good’ or ‘bad’ and lectins seem to get pushed into the ‘bad’ category. But that’s not always the case. They can be harmful but there are ways and means to get around that. Yeh, but what are lectins?
Lectins can be found in plants, animals and bacteria; they are part of a defence mechanism, essentially. Their correct definition is ‘a carbohydrate binding protein’. Yikes what is that? – It doesn’t mean anything!! Ok so we don’t normally like to get to the science part so early but in this case it might be necessary!
Simplified version alert! Let’s take lectins in our bodies first. Imagine that a pathogen enters our body, how does our body know that it is not part of it and should be marked for destruction? If it has visited before, the body might recognise it, as it will have built up antibodies to that particular pathogen but that takes time. If it’s a new kid on the block then it needs to be tagged.
The pathogen has sugars on its surface and depending on the arrangement of those sugars this will identify it as foreign. This is where lectins come in because they are sugar binding proteins and have this ability to stick like Velcro to the pathogen and show it for what it is. So really they are part of our immune system. That’s only one of the functions but we won’t go into the rest because it’s a bit complicated and we are only interested in lectins in food at the mo.
It’s a defence thing with plants too as plants need to grow and thrive and to protect themselves from being eaten by insects and other stressors like extreme temperatures, drought etc; so they have lectins as their defence. Some of these lectins can be quite vicious; the most toxic probably from the castor bean and it is called ricin – yes lethal…..
This family of proteins can be found in most foods to varying degrees but the ones that cause the most problems are grains (especially wheat, known as wheat grain agglutinin (WGA)), beans, legumes (especially soy), dairy and the nightshade family of vegetables (tomatoes, peppers, aubergines and potatoes). To stop them creating havoc in our guts we can get around it by soaking, fermenting, sprouting and cooking them properly!
Negative aspects of lectins
Humans can have problems digesting lectins as they are resistant to our body’s digestive enzymes and tend to pass through our stomachs unchanged.
Because of their super glue like qualities lectins from plant foods can attach themselves to our intestinal wall and have a similar effect on it that gluten does (see gluten blog for details!) creating the situation for leaky gut. The real problem begins if they do enter the blood stream because of their ability to bind to almost any type of cell and cause damage to different organs.
This has associated them with autoimmune conditions (wheat grain lectins link to rheumatoid arthritis being an example) and inflammation, as damage to the intestinal wall can lead to a broader immune system response. So the combo of gliadin (one of the proteins in gluten) and WGA could be the old one two for some peoples guts!
If enough lectins are consumed (or not cooked properly) it can cause damage to the gut lining which can invoke symptoms similar to food poisoning. Our body’s reaction is to go into evacuate mode to get rid of the source of irritation. Kidney beans are probably one that most people have heard of that can cause problems. They are in fact poisonous if not soaked and cooked properly. The lectin responsible for this is called phytohaemagglutinin (why are they always unpronounceable?!)
Anyone with conditions like Crohn’s disease or IBS may be more sensitive to food lectins due to the high turnover of cells in their gut lining. This leaves the gut with a higher proportion of immature cells which gives ideal opportunity for the lectins to use their sticky fingers on!
Note of caution here; in our modern world genetically modified (GM) food is becoming more prevalent. The GM soybean needs attention in particular. Not only is it genetically modified to be more tolerant to the herbicide glyphosate( yes it has been altered so that it tolerates a herbicide!) but it has been found to have double the amount of soy lectin in it and an increased amount of soy allergen. This doesn’t bode well for our future health – especially when a lot of our meat and dairy comes from animals fed GM produce. Another reason to go organic! The insecticidal effects of lectins are used in the biotechnology industry to produce, on a commercial scale, crops that are tolerant to insecticides.
Mucilaginous foods to the rescue
Well what is a mucilaginous food and what does it have to do with lectins?! Some seaweeds and what are known as mucilaginous foods can bind to lectins so they don’t stick to our guts. Some of these friendly foods include oats, apple pectin, flaxseeds, chia seeds, okra and figs. There are also popular tummy demulcents which have been used historically such as slippery elm and marshmallow root. It’s now making sense why these help an irritated gut.
Positive aspects of lectins
Exciting research is going on regarding the use of lectins from plant and animal sources in anti- cancer treatment. One of the main ones of interest is the mistletoe (?) lectin. Yes, quite because mistletoe is actually poisonous if ingested so don’t go eating it! The interest is of course to somehow use the lectins capability to programme cell death in the cancer cells and somehow harness that capability without the toxic effects on other tissues. There has also been some research on chickpea lectins and breast cancer.
Other research going on is the harnessing of lectins against bacterial and fungal infections. There is also interest in using lectins in pharmaceutical drugs because of their super glue qualities to target and deliver these drugs exactly where they need to be aimed.
Now, there is an interesting hypothesis linking lectins to the obesity crisis. But we need to know what leptin is and also what leptin resistance is!
Leptin is a hormone produced by fat cells and one of its jobs is to send a signal to our brain to tell us we have eaten enough and are full. Obese people tend to have high levels of leptin circulating in their system and so it is thought they have what is known as leptin resistance. Their cells do not respond to the leptin, so the signal never gets to the brain to say ‘stop eating!’! Yes but what does that have to do with lectins? Lectins/ leptin it’s all getting a bit confusing!
Well, the hypothesis is linked to a cereal based diet being a factor in obesity. It is proposed that the human leptin system is ‘insufficiently adapted’ to this diet. It is thought that the wheat grain lectin in particular may be binding to the cell receptor that the leptin is supposed to attach itself to and consequently throwing the whole system out of whack! It’s still an area being researched and isn’t the only reason we can pile on the pounds but it might explain why foods made from flour just make us want to eat more!
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