Are lectins bad for Health? the anti-nutrient truth

Have you heard about the carnivore diet?

Advocates of this diet only consume animal products. One of their claims against eating plants is that these contain “anti-nutrients”. These anti-nutrients are thought to interfere with how the body absorbs nutrients from the gut into the bloodstream. Examples of these are phytates, tannins, lectins, and oxalates.3

If these substances are so damaging, how is it possible that a plant-based diet is optimal for humans? How is it possible that the longest-lived people on Earth eat 95% plants and live to past 100 on average?

As you will see later in this post, not everything that happens in a petri dish is the full truth. Sometimes, other factors come into play that changes the outcome. To explain this concept, I will be talking about one category: lectins. 

 

What are plant lectins?

Lectins (or hemagglutinins) are a group of proteins that bind to carbohydrates. They are found in most plants but are present in high concentrations, especially in grains, nuts, and legumes. Their main function is to protect plants against external pathogens,1 including, us? 

To put an example, the lectin found in wheat germ (the inside part of the wheat grain) is called wheat germ agglutinin (WGA) and has been intensively studied. One of the characteristics that make these proteins unique is their resistance to degradation, including the degradation process that happens during digestion. In fact, WGA consumed by people travels through the intestine and appears in the feces in its intact form.2

Great! You might think. We just poop them out without negative effects, like when we quickly eat a meal containing whole corn, or when we add flax seeds to our morning oatmeal without grinding them first. What is the problem with lectins then?

 

Beans 1

 

Lectins can be harmful to us.

Like I mentioned earlier, these proteins can bind to carbohydrates, which are part of cell membranes that recover the intestinal and colonic mucosa.2 The mucosa is the mucus-like layer that recovers the intestines and any other surface of our body such as lungs and skin. This protein-carbohydrate binding leads to negative effects on the gut epithelium, including changes in cell morphology, growth, and behavior. This compromises the functions of the digestive tract, causing gut inflammation, leaky gut, and reduced nutrient uptake.1, 2, 5

The harmful effects of lectins do not only affect the digestive tract. Lectins can enter the cells by endocytosis and be released into the intracellular space, from where can be transported and deposited inside the blood and lymphatic vessels.2

What’s more, lectins also seem to stimulate an immune response. For instance, they stimulate the production of specific IgA and IgG antibodies, as well as trigger histamine release by basophils (type of immune cells). This effect, together with the increased translocation of food particles and bacteria through the intestinal layer, may contribute to the development of rheumatoid arthritis.2

 

Figure 2

 

So, should we not eat plants?

You probably noticed that people from everywhere over the globe eat plants and seem to live happy and healthy lives. In fact, consumption of foods containing lectins is associated with reduced risk for type 2 diabetes, cardiovascular disease, long-term weight management, and even certain types of cancers! These effects are largely attributed to the fiber and phytochemicals found in whole grains, legumes, nuts, and fruits.1, 3, 5, 7

And this is where petri dish-isolated science and real-life conflicts.

  1. Scientists have investigated the positive and negative outcomes that occur when lectins interact with our cells using intact, isolated “raw” lectins.3 And that makes sense! Researchers need to mimic what nature created: whole, intact proteins. However, humans do not eat raw beans, grains, or potatoes. We usually sprout, soak, and/or cook them. This is a very important step because it destroys the lectins, and they are not able to trigger cellular changes anymore in the gut.
  2. We don’t eat isolated lectins in the quantities that have been tested in a petri dish or animal models.

 

Beans 2

 

Potential anti-cancer properties of lectins

The small amounts of remaining lectins found in cooked foods are not damaging anymore.

What’s more, they seem to have impressive anti-cancer properties!

I have previously mentioned that lectins can activate the immune system and when uncontrolled, become damaging. However, when trying to boost the immune system with a vaccine, certain agents can be used to trigger a bigger reaction. Currently, lectins are being studied for this!4, 8 In vitro, lectins can kill and/or stop the growth of certain types of cancers.1, 3, 6

Something really interesting is that lectins bind carbohydrates in a very specific manner. Cancer cells express different carbohydrates on their surface (different glycosylation patterns), and this is fantastic! Researchers are currently studying how to use certain lectins to direct chemotherapy agents to target only cancer cells.3, 9, 10

 

Tips to minimize lectins in foods

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My view

I don't think we should worry about lectins at all. Research has proven that cooking, sprouting, and/or soaking nuts, legumes, and grains destroy most of the lectins. The anti-nutrient theory is only right when eating these foods in their raw form!

Moreover, there is an exciting future for lectins as they are being studied to be used as adjuvants in vaccines and in chemotherapy.