Megapost : First Gluten was identified. Now comes lectins, found in wheat, grains, rice, potatoes etc. Lectins can impair digestive health, mental health, cardiovascular health, and cellular function. Lectins can contribute to weight gain and diabetes, and can impair your immune system.
I continue to be interested in paleolithic diet theory. We’ve only been eating milk and grains for 10,000 years, and it takes considerably longer than that to adapt to new food groups. So it is therefore likely that we do not have the right biological structures in place to deal with those foods. As time goes by research increasingly supports this conclusion. We know that certain proteins in dairy products are linked with heart disease and poor circulation. We know that gluten can cause a plethora of problems even in those who test negative for celiac. We’re just beginning to scratch the surface when it comes to other components in other grains and dairy.
First let’s go over WGA, or wheat germ agglutinin, and the issues it brings up.
Lectin is a defense mechanism for the wheat plant, designed to ward of its natural enemies such as fungi and insects. Unfortunately, this protein is also very resistant to breakdown by living systems, and it easily accumulates in tissues where it interferes with normal biological processes and acts as an anti-nutrient.
Pro-Inflammatory: WGA lectin stimulates the synthesis of pro-inflammatory chemical messangers, even at very small concentrations.
Immunotoxic: WGA lectin may bind to and activate white blood cells.
Neurotoxic: WGA lectin can pass through your blood-brain barrier and may attach to the protective coating on your nerves known as the myelin sheath. It is also capable of inhibiting nerve growth factor, which is important for the growth, maintenance, and survival of certain target neurons.
Cytotoxic (Toxic to cells): WGA lectin may induce programmed cell death.
Further, research shows WGA lectin may even:
Interfere with gene expression
Disrupt endocrine function
Adversely affect gastrointestinal function
WGA lectin is capable of passing through cell membranes of your intestines, gaining entry into your body. Further, if your mucosal barrier is compromised, for instance from taking certain drugs like aspirin and ibuprofen or due to a viral or bacterial infection, lectin may become even more problematic.
Keep in mind that lectin is not only in wheat. All seeds of the grass family (rice, wheat, spelt, rye, etc.) have high levels of lectin.
WGA lectin is an exceptionally tough adversary as it is formed by the same disulfide bonds that make vulcanized rubber and human hair so strong, flexible and durable. Like man-made pesticides, lectins are extremely small, resistant to break-down by living systems, and tend to accumulate and become incorporated into tissues where they interfere with normal biological processes. Indeed, WGA lectin is so powerful as an insecticide that biotech firms have used recombinant DNA technology to create genetically modified WGA-enhanced plants.
Lectins are glycoproteins, and through thousands of years of selectively breeding wheat for increasingly larger quantities of protein, the concentration of WGA lectin has increased proportionately.
Lectins are designed “to choose” specific carbohydrates that project off the surface of cells and upon which they attach. In the case of WGA the two glycoproteins it selects for, in order of greatest affinity, are N-Acetyl Glucosamine and N-Acetylneuraminic acid (sialic acid).
All animals, including worms, fish, birds and humans, use N-Acetyglucosamine as a foundational substance for building the various tissues in their bodies, including the bones. The production of cartilage, tendons, and joints depend on the structural integrity of N-Acetylglucosamine. The mucous known as the glycocalyx, or literally, “sugar coat” is secreted in humans by the epithelial cells which line all the mucous membranes, from nasal cavities to the top to the bottom of the alimentary tube, as well as the protective and slippery lining of our blood vessels. The glycocalyx is composed largely of N-Acetylglucosamine and N-Acetylneuraminic acid (also known as sialic acid), with carbohydrate end of N-Acetylneuraminic acid of this protective glycoprotein forming the terminal sugar that is exposed to the contents of both the gut and the arterial lumen (opening).
WGA is an exceedingly small glycoprotein (36 kilodaltons)
Lectins … are notoriously dangerous even in minute doses and can be fatal when inhaled or injected directly into the bloodstream. According to the U.S. Centers for Disease Control it takes only 500 micrograms (about half a grain of sand) of ricin (a lectin extracted from castor bean casings) to kill a human.
The main source of glucosamine on the market is from the N-Acetylglucosamine rich chitin exoskelotons of crustaceans, like shrimp and crab. Glucosamine is used for reducing pain and inflammation. We do not have a dietary deficiency of the pulverized shells of dead sea critters, just as our use of NSAIDs is not caused by a deficiency of these synthetic chemicals in our diet. When we consume glucosamine supplements, the WGA, instead of binding to our tissues, binds to the pulverized chitin in the glucosamine supplements, sparing us from the full impact of WGA.
At exceedingly small concentrations (nanomolar) WGA stimulates the synthesis of pro-inflammatory chemical messengers (cytokines) includingInterleukin 1, Interleukin 6 and Interleukin 8 in intestinal and immune cells. WGA has been shown to induce NADPH-Oxidase in human neutrophils associated with the “respiratory burst” that results in the release of inflammatory free radicals called reactive oxygen species. WGA has been shown to play a causative role in patients with chronic thin gut inflammation.
WGA induces thymus atrophy in rats and may directly bind to, and activate, leukocytes. Anti-WGA antibodies in human sera have been shown to cross-react with other proteins, indicating that they may contribute to autoimmunity. Indeed, WGA appears to play a role in the pathogenesis of celiac disease (CD) that is entirely distinct from that of gluten, due to significantly higher levels of IgG and IgA antibodies against WGA found in patients with CD, when compared with patients with other intestinal disorders. These antibodies have also shown not to cross-react with gluten antigens
WGA can pass through the blood brain barrier (BBB) through a process called “adsorptive endocytosis” and is able to travel freely among the tissues of the brain which is why it is used as a marker for tracing neural circuits. WGA’s ability to pass through the BBB, pulling bound substances with it, has piqued the interest of pharmaceutical developers who are looking to find ways of delivering drugs to the brain. WGA has a unique binding affinity for N-Acetylneuraminic acid, a crucial component of neuronal membranes found in the brain, such as gangliosides which have diverse roles such as cell-to-cell contact, ion conductance, as receptors, and whose dysfunction has been implicated in neurodegenerative disorders. WGA may attach to the protective coating on the nerves known as the myelin sheath and is capable of inhibiting nerve growth factor which is important for the growth, maintenance, and survival of certain target neurons. WGA binds to N-Acetylglucosamine which is believed to function as an atypical neurotransmitter functioning in nocioceptive (pain) pathways.
WGA has been demonstrated to be cytotoxic to both normal and cancerous cell lines, capable of inducing either cell cycle arrest or programmed cell death (apoptosis).
WGA may prevent DNA replication. WGA binds to polysialic acid (involved in posttranslational modifications) and blocks chick tail bud development in embryogenesis, indicating that it may influence both genetic and epigenetic factors.
WGA has also been shown to have an insulin-mimetic action, potentially contributing to weight gain and insulin resistance
WGA induces platelet activation and aggregration. WGA has a potent, disruptive effect on platelet endothelial cell adhesion molecule-1, which plays a key role in tissue regeneration and safely removing neutrophils from our blood vessels.
WGA causes increased shedding of the intestinal brush border membrane, reduction in surface area, acceleration of cell losses and shortening of villi, via binding to the surface of the villi. WGA can mimic the effects of epidermal growth factor (EGF) at the cellular level, indicating that the crypt hyperplasia seen in celiac disease may be due to the growth-promoting effects of WGA. WGA causes cytoskeleton degradation in intestinal cells, contributing to cell death and increased turnover. WGA decreases levels of heat shock proteins in gut epithelial cells leaving these cells less well protected against the potentially harmful content of the gut lumen.
However, it makes sense to be concerned about foods other than wheat:
There are other lectins in the Western diet that have properties similar to wheat lectin (WGA), namely, “chitin-binding lectins.” Remember, “chitins” are long polymers of n-acetyl-glucosamine, the primary binding target of wheat lectin. Wheat lectin and “chitin-binding lectin” therefore share functional similarities.
Antigenically similar chitin-binding lectins are present in the embryos of wheat, barley, and rye, members of the Triticeae tribe of the grass family (Gramineae).
Similar lectins were not detected in oats and pearl millet, members of other tribes of the Gramineae. Rice, a species only distantty related to wheat, contains a lectin that is antigenically similar to the other cereal lectins and located at the periphery of embryonic roots and throughut the coleoptile.
Intranasal delivery of tomato lectin (LEA) elicited a strong lectin-specific systemic and mucosal antibody response but only weakly potentiated the response to co-delivered OVA. In contrast, administration of wheatgerm agglutinin (WGA) or Ulex europaeus lectin 1 (UEA-I) with OVA stimulated a serum IgG response to OVA while the lectin-specific responses (particularly for WGA) were relatively low.
However, there is some evidence tomatoes actually reduce inflammation because they also contain a number of compounds that are beneficial to health.
Of course tomatoes and the nightshade family also contain alkaloids which have negative effects on health. These amounts are clearly sufficiently low that we don’t notice it much.
Four kinds of alkaloids in the Solanaceae family include the steroid alkaloids (the alkaloid found in most nightshade foods), tropane, pyrrolizidine and indole alkaloids. Steroid alkaloids have been shown to block certain nerve activity that can, at high levels, cause muscle shaking, paralysis and respiratory difficulty. They have also been associated with inflammation, particularly in the joints. Finally, some nightshade foods like eggplant and tomato contain trace amounts of nicotine.
The essential point of the paleolithic diet is that humans didn’t discover that cooking made grains, beans, potatoes and other foods edible until 10,000 years ago. Since it takes 100,000 years to adapt to a new food group, it is likely that our bodies can not handle these foods well.
Tomatoes are actually interesting because they are in the nightshade family - the same family as potatoes. Here is some tomato history.
The Tomato History has origins traced back to the early Aztecs around 700 A.D; therefore it is believed that the tomato is native to the Americas. It was not until around the 16th century that Europeans were introduced to this fruit when the early explorers set sail to discover new lands.
Genetic evidence shows the progenitors of tomatoes were herbaceous green plants with small green fruit and a center of diversity in the highlands of Peru.
So the idea is that tomatoes are a relatively new, foreign fruit, more related to the foods that are bad for us than the foods that are good for us. The prominent members of the nightshade family are potato (except sweet potatoes and yams), tomato, eggplant, tobacco, and peppers (except black and white pepper) (includes paprika, chipotle, & cayenne).
It’s possible that we could discover that tomato lectins are not as harmful as other lectins, but I feel that given the large number of fruits out there, cutting out one is no big deal.
Tomatoes are famous for lycopene, but watermelon and papaya are also great sources there.
Source μg/g wet weight
Raw tomato 8.8–42
Pink grapefruit 3.6–34
Pink guava 54
Some of the other effects of lectins are interesting to me. For example, here is a possible link between lectins and psoriasis. Of course grains have a number of anti-nutrients and while researching this, I came across benzoxazinoids, which are contained in wheat, maize, and rye, and apparently can be somewhat mutagenic.
Of course this is also an argument in favor of cutting out any type of meat that are fed grains. So the eliminates any meat that’s not grass fed. It also eliminates eggs, as almost all chickens are fed grains of some sort, even so-called pastured chickens. I thought this was interesting:
I’ve read anecdotes from celiacs who have reacted to eggs from chickens fed wheat, but not from chickens fed corn.
It is my bet that there are lot of problems associated with eggs that stem directly from the fact that modern chickens are fed wheat, soy and corn - 3 foods disallowed by the paleolithic diet. Just as meat is unhealthy, partly because of what cows are fed, in comparison to grass fed beef, my bet is eggs are not as healthy as they might be if chickens ate insects and other foods for which they were evolutionarily designed.