Lectins are proteins that protrude from a cell’s surface, allowing it to interact with its surroundings. This article compares lectins to Velcro: they’re sticky, and while each individual attachment is weak, the composite effect is strong.
Lectins are everywhere: your cells have them, bacteria have them, and most of your food has them too, though to varying degrees. The highest lectin-containing foods include legumes, grains (including grain-fed animal products), dairy, corn, and nightshade veggies (such as tomatoes, peppers, eggplants, and potatoes). Within your own body and in those of animals, lectins perform some valuable functions: they help your immune cells to adhere to a site of injury, produce blood clotting, and healing. In plants, they act as insecticides, though they may have other functions as well.
But can consuming these sticky proteins in your food have a damaging effect on your health? According to the Low Lectin Diet popularized by Dr Stephen Gundry, the answer is yes. Here’s the idea behind this.
Lectins as Anti-nutrients
Because lectins are designed to be sticky, they resist digestion. You might notice that the foods on the high lectin list include almost all of the most common allergens and food sensitivities, and this may be the reason why. Lectins are also resistant to digestive enzymes–so while people with robust guts can usually handle breaking down “sticky” proteins, those with weaker digestive systems might have more of a problem.
This is also why lectins tend to act as “anti-nutrients”. If you’re not digesting your food properly, then you’re not able to extract its nutritional value. This means the bacteria in your gut have to break your food down for you, leading to a shift in your microbiome (and probably not for the better).
Lectins and Inflammation
According to this article, the lectin called Wheat Germ Agglutinin (WGA) triggers inflammation, including release of cytokines and histamine. This is a separate issue from gluten sensitivity, though it’s probably a contributing factor.
I haven’t found studies that support the idea that other lectins besides WGA are specifically inflammatory. But this article links lectins generally, and wheat in particular (at least as far as studies to back it up go) with Celiac Disease, diabetes, and Rheumatoid Arthritis. In the case of Celiac, the connection is obvious, as Celiac is the autoimmune destruction of the small intestine villi in response to the gluten protein; in the case of the others, it is either due to molecular mimicry, or simply because there is an inflammatory process going on already. Any increased inflammation in the gut (where some 80% of the immune system resides) will only worsen the problem.
Lectins and Leaky Gut Syndrome
Again, this article shows that WGA is associated with “leaky gut syndrome,” or increased intestinal permeability. I haven’t found studies to back up the idea that other lectins do the same.
That said, the “sticky” nature of lectins in general will make any of them hard to digest. If your enzymes can’t do the job, the undigested food will recruit bacteria to do so for you, leading to dysbiosis, or imbalanced gut flora. This will set you up for inflammation, which can lead to leaky gut syndrome. So I wouldn’t rule out the idea that other lectins can lead to leaky gut, as well.
Do You Need To Avoid Lectins?
So do we have to avoid high lectin foods entirely?
I believe the answer is no–for most of us. While lectins are heat resistant, boiling and pressure cooking both work well to break down lectins such as legumes and grains. Both of these high lectin foods also can become much easier to digest by soaking or sprouting them before cooking. This renders them far easier to digest. Sprouting and fermentation also help to degrade lectin content, and this is likely part of why even those who are gluten sensitive can often tolerate sourdough or sprouted bread.
Peeling and removing seeds will decrease lectin content, as well, as the highest concentration of lectins are in the seeds and skin. This would primarily apply to the nightshades such as peppers, tomatoes, and eggplants–though personally, given the current state of the research, I tend to think this is overkill. If you are sensitive to nightshades, avoid them entirely. If you’re not, I’m not convinced this step is necessary. (Just my $0.02.)
Corn and soy (in the legume family) are two of the most commonly genetically modified foods today. They are also very common allergens and sensitivities. If you’re not sensitive to them, I would still recommend purchasing these organic, or with the “non-GMO” label.
As for grain-fed animal products: it’s definitely best to choose grass-fed and organic whenever possible, though not necessarily because of the lectin content.
And dairy is a complex topic—while I don’t think everyone needs to avoid it on general principle simply due to lectin content, I do think it has been adulterated via many of our processing methods. Some people are so sensitive that they do need to avoid it entirely, and it is a very common IgG food reaction—perhaps due to the lectin content. But there are a number of other reasons why dairy is tolerated far less today than it has been historically.
Lectins may or may not be the underlying reason why the foods on the high lectin list tend to be so problematic. Either way, there are other good reasons to at least be careful of the foods on this list. Some good rules of thumb for everyone:
- Soak your legumes and grains before cooking them, and then cook them by boiling or using a pressure cooker.
- Always choose organic or non-GMO corn or soy.
- If you eat bread, choose sprouted and/or sourdough, and 100% whole grain.
If you suffer from unexplained health problems, I would either get an IgG food sensitivity test to see if the high lectin/common allergen foods are a problem for you, or else consider a trial elimination of the foods on this list. See if you feel better without them!