Lectins are one of the damaging food components that we hear the least about. We hear about gluten, casein, oxalates, glutamate, and so many other dietary components that can factor into poor gut health but rarely lectins. So, what are they? They serve many functions in different organisms, but the ones that we get the most of from our diet (and that appear to be the most toxic) are essentially natural pesticides evolved by plants for protection. The foods with the highest concentration are wheat and other grains, soy, legumes (including peanuts), dairy, and nightshades. Lectins cause damage to the cells lining the intestines, which compromises gut integrity (causes leaky gut syndrome), impair the ability of the gut to absorb nutrients (they are a potent anti-nutrient), and are also associated with autoimmunity. Lectins have also been implicated in leptin resistance- leptin is a hormone that regulates appetite and metabolism, and leptin resistance is associated with both diabetes and obesity.
This post on Mark's Daily Apple, which is an excellent discussion of dietary lectins, lists several ways to reduce dietary intake of lectins. This includes elimination of the foods with the highest concentrations (grains and soy), possible reduction of intake of foods relatively high in lectins including nightshades, beans, and dairy, as well as soaking and fermenting foods to reduce or eliminate their lectin content. Another article, Food Lectins in Health and Disease, An Introduction, goes into more depth about the various types and varying toxicity of different lectins. Some are deadly to humans in any amount, while other may actually provide health benefits such as protection from cancers. Interestingly, lectins are what is used to test for blood type and this article suggests that this may be the basis for the idea of blood type diet. The mechanism for this is the fact that certain lectins cause clumping of red blood cells, which is interesting because the clumping of red blood cells has been observed in some people with autism and I believe has even been linked to the virus that Roo and I have, HHV-6. The following is a quote from this article that I find especially interesting:
"Wrong types or levels of good and bad bacteria in the gut, or intestinal dysbiosis, may contribute to this process of abnormal stimulation of the immune system. Research supports the strong possibility that such stimulation may be accentuated by interaction of the bacteria with food lectins. It is believed by some that this may further worsen gut injury and autoimmune disease."
According to the entry in Wikipedia, "They play a role in biological recognition phenomena involving cells and proteins. For example, some viruses use lectins to attach themselves to the cells of the host organism during infection." This article from Wikipedia also states that lectins can cause irritability in the gut that leads to excess mucous production- I wonder if this is another reason why the Specific Carbohydrate Diet is effective? Elaine Gottschall, who popularized the SCD, emphasized the need to reduce excess mucous in the gut via the diet. The article also discusses various biochemical processes in humans that are effected by or regulated by lectins, which leads me to wonder if dietary lectins that enter the bloodstream via a leaky gut can disrupt those processes?
Some lectins are implicated in allergic responses. According to the study "Interactions of Lectins with Human IgE: IgE-binding property and histamine-releasing activity of twelve plant lectins", some of the lectins tested were associated with histamine release from basophils in allergic patients. Another article goes into more detail about the role of lectins in both inflammatory and immune processes:
This is another connection with the HHV-6 virus; patients with chronic active HHV-6 have reduced NK cell activity.
The following is a list of things that lectins are capable of doing, according to the sources linked to in this post:
-limit release of digestive enzymes
-increase appetite
-bind to insulin receptor sites on cells and trigger the storage of fat
-cause leaky gut
-alter gut flora
-damage intestinal villi
-impair the absorption of nutrients
-cause leptin resistance
-mimic hormones
-regulate immunity
-cause and worsen inflammation
-cause and worsen autoimmunity, especially Rheumatoid Arthritis
-clumping of red blood cells
-inflammation and enlargement of the pancreas and liver
-trigger release of histamine from basophils
-implicated in connective tissue disorders
For further reading:
Do dietary lectins cause disease?
