Molecular stucture of Concanavaline A lectin
You’ve probably been hearing about yet another diet fad – the lectin-free diet. Does this newest fad trailing a host of previous fads have any validity? Will it help you lose weight and reduce inflammation? Are lectins really toxins?
Like the gluten-free fad that preceded it, and the litany of so many other fad diets, the lectin-free diet is a misrepresentation of selective research studies that paint lectins as poisons or toxins.
Promoters of the lectin-free diet have accused foods that are supposedly high in lectins as causing leaky gut syndrome and increased inflammation.
Their claim is that by reducing intake of certain foods, primarily beans, grains, tomatoes, potatoes and “nightshade” vegetables, we can decrease inflammation and lose weight.
Certainly, as the gluten-free diet proved, if we stop eating a good portion of the foods humans have been eating for thousands of years, we might lose some weight. But is the weight loss merely a result of an onerously selective diet, resulting in a reduction of calories?
To answer the questions above about the lectin-free diet, let’s look objectively at the facts.
In this article
What is a lectin?
Lectins are proteins that exist throughout nature. They are present in practically every animal, practically every unicellular creature, and in most, if not practically all plants. Lectins are parts of plant roots, plant leaves, stems and flowers.
Lectins are complicated, and they are difficult to isolate. Over the past two decades, dozens of lectins have been isolated using complex purifying techniques. But most researchers agree that there are likely thousands of different types of lectins throughout nature.
A general definition of lectins relates to their ability to help bind compounds. These include proteins, carbohydrates, fats and other molecules in the body. Lectins are multifaceted and there are many types of lectins.
Lectins also exist in all animals. In animals – including humans – lectins have many metabolic functions. Lectins help the body’s cells in their DNA production and replication. They assist the immune system by fighting inflammation, infections by viruses and bacteria, and protecting organs from outside invaders and toxins.
We have discussed other research showing that lower levels of lectins in humans and animals leads to greater risk of infections.
Lectins are responsible for making sure our blood coagulates so we won’t bleed to death. Lectins are responsible for killing cancer cells, which the body produces on a regular basis. Lectins help maintain our blood vessel health and help them expand and contract.
Lectins help the liver function properly in the face of various toxins. Lectins help us process carbohydrates to convert them into energy. Lectins help our immune systems recognize invading viruses, bacteria and other entities that are not healthy.
The list goes on and on. Lectins are critical to the health of our body. Without lectins, our body is not protected.
These include binding proteins to proteins, fats and proteins, carbohydrate processing, DNA activity, and so much more carbohydrates and proteins, structures other than carbohydrates via protein-protein, protein-lipid or protein-nucleic acid interactions.
While animal lectins undoubtedly fulfill a variety of functions, many could be considered in general terms to be recognition molecules within the immune system. More specifically, lectins have been implicated in direct first-line defense against pathogens, cell trafficking, immune regulation and prevention of autoimmunity.
And some lectins are known to bind to bacteria and viruses and other foreign elements – helping to protect cells from their intrusion. We have discussed research showing that lectins fight viruses.
In fact, this is one of the central benefits for these important proteins in plants. They help protect the plants that produce them from being harmed by bacteria and viruses. They do this through molecular affinity, and the binding-reception process that takes place on the surface of most cells.
In plants, lectins also have a variety of other purposes. These including binding to carbohydrates and assisting the plant’s immune system deter infections. Lectins in plants help the plant grow strong and stay protected against the elements.
These abilities of immunity-related plant lectins actually make them healthy for humans. Lectins or lectin-produced compounds in plants have proven over and over to aid human health.
Lectins and lectin-produced compounds in plants form most of the protective elements in plants. These relate directly to fibers, antioxidants and so many other health-giving compounds.
Lectin-free diets over-generalize lectins
In other words, lectins are found everywhere, throughout nature. They conduct so many processes that it is unreasonable to define them as toxins in general, because most are required for survival. Lectins are contained in just about every plant food, including bananas, coconuts, potatoes, beans, nuts, seeds, vegetables and so many other health-promoting foods. To define them as anything but health-promoting is to look at health through a very narrow bandwidth indeed.
Lectins bind with innumerable molecules involved in millions of life-sustaining biological processes. Some of them are particularly healthy. For example, lectins from Wisteria japonica bind with cancer cells but not normal cells, just as lectins from wheat germ do.
This is not to say that all lectins are healthy. Ricin, for example, is a lectin. It is a lectin found within castor beans of the castor plant (Ricinus communis). But then castor beans haven’t been part of the human diet either.
Just as beans, nuts, seeds, potatoes, coconut and many other foods with lectins are healthy, lectins in wheat and wheat germ are also healthy, as I proved in my book, “The Gluten Cure.”
Example: Wheat germ lectin
Wheat germ, for example, has been shown in several human clinical studies to reduce intestinal inflammation, boost liver health, stimulate immunity and help normalize cholesterol levels. In a study from France’s INSERM (National Institute of Health and Medical Research) (Cara et al. 1992) researchers found that lectin-containing wheat germ reduced triglycerides, improving cardiovascular health.
Proteins called lectins can also form a clumping – in this case often to polysaccharides or carbohydrates.
And as far as the agglutinin in wheat germ – yes, a particular type of lectin protein called wheat germ agglutinin (WGA) will bind to a glucose derivative called N-Acetylglucosamine. And note that wheat germ agglutinin – or WGA – is unrelated to gliadin and glutenin proteins termed ‘gluten.’
The investigation into WGA’s effect upon the intestines has provided some grist for gluten-free advocates. But what must be examined with the science is the context and rationale for studying WGA lectins.
Many food plants produce lectins as a natural part of their immunity, so it is important for food scientists to understand the effects of these lectins from an isolated viewpoint – out of the context of normal dietary use of the foods they are contained within.
Can lectins cause leaky gut syndrome?
This is perhaps the central argument of the lectin-free diet proponents. They claim the research overwhelmingly shows lectins produce leaky gut. Well, certainly not all lectins do this. And under normal conditions, the one lectin shown to bother the gut wall is neutralized by a healthy gut before it even reaches the intestinal walls.
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A 2009 laboratory study from Italy’s University of Verona is quoted by many lectin-free diet proponents. The study abstract states that wheat germ agglutinin (WGA) “is a toxic compound and an anti-nutritional factor.” In the same sentence they add, “but recent works have shown that it may have potential as an anti-tumor drug…”
Besides the question of why WGA lectin is toxic yet it kills cancer, the primary question relates to the setting of the study. The tests that rendered this conclusion was a laboratory that utilized cultured gastrointestinal cells called Caco-2 cells.
Yes, the study found that WGA, at certain doses, can provoke an inflammatory response, specifically by intestinal Caco2 cells. However, in this study, the cells also produced an immune response that balance these effects with cytokines.
The most disturbing thing is that the researchers were not duplicating the gastrointestinal system. They were culturing some intestinal cells in Petri dishes. What about all the other stuff in the human gastrointestinal tract, such as enzymes, probiotics, immunity cells (such as IgA), proteases which break apart proteins such as WGA, and so many other aspects of the human digestive tract?
Cultured intestinal cells within Petri dishes in a laboratory environment is not our gut. It does not duplicate all of the elements involved in human digestion – including the probiotic-rich mucin layer that in a healthy intestinal tract protects the intestinal cells from such exposures.
Rather, the researchers simply exposed isolated intestinal cells to purified WGA and watched the immune response within the laboratory. Such a response, in fact, would occur with many raw food compounds in such isolated conditions.
At the same time, however, other research has illustrated that a vast range of WGA doses are safe and non-inflammatory in a healthy intestinal tract. But when doses are given that dramatically exceed a normal human diet – the equivalent to over 600 grams for an adult male (over a pound of not just wheat germ but a pound of purified WGA lectin in one sitting) – intestinal inflammation can occur if WGA is not broken down before exposure to intestinal cells.
Not only was the quantity far greater than any realm of realism in the lab study above, but the WGA was not within the natural matrix of plant nutrients.
As examined in my book, our bodies produce particular proteases which break apart proteins such as WGA. We also host probiotics that break them down, and have protective layers that help shield the intestinal cells against exposure to undigested proteins.
Cooking inactivates WGA lectins
Furthermore, research has indicated that much of wheat germ agglutinin is neutralized by cooking. A study by researchers from Italy’s University of Verona (Matucci et al. 2004) determined that WGA lectin is largely deactivated at cooking temperatures of 65 degrees Celsius (about 149 degrees Fahrenheit).
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The researchers found WGA in raw flour but found that resulting breads had significantly reduced WGA lectin levels.
This means that baking and fermenting (with yeast) with whole wheat flour will largely inactivate wheat germ agglutinin.
This also goes for many other lectin-containing foods. Especially those such as beans and nightshade foods. Who eats beans raw? No one. Cooking beans will break down most of their lectin content – even if we consider them so bad.
As for other supposedly higher lectin foods such as coconuts, whole grains, tomatoes and nightshades: These foods have been tested in large-scale human diet studies and shown to be seriously healthy. Diets that include these foods have been shown to be extremely heart-healthy and cancer-preventative.
Isolated lectins are not normal foods
But should a lab isolate and purify a huge dose of practically any protein – especially a protein that is a known lectin: There certainly will be intestinal consequences. These would relate to the fact that the protein was not properly broken down, as happens in our intestinal tracts.
Isolated and purified lectins – as found in the above studies – are not normal foods. It is like isolating and purifying sugar from beets. Beets are healthy foods that provide significant nourishment. But when refined sugar is isolated and purified from beets (and cane) – as has been done over the past century: That sugar becomes a cause of diabetes, metabolic disease, heart disease and other conditions.
Should we stop eating whole beets because sugar gets extracted from them?
Even with doses considered healthy, WGA has been shown to be selectively cytotoxic to human colon cancer cells (Pusztai et al. 1993 and others). The WGA was able to select, bind to and destroy colon cancer cells while leaving the healthy intestinal cells alone.
So WGA is actually – as many lectins are – pretty smart. And beneficial to humans.
This simply means that within a healthy diet and healthy intestinal tract, food lectins such as WGA are not only safe for human consumption, but help protect against colon cancer.
Wheat germ, for example, has been shown in several human clinical studies to reduce intestinal inflammation, boost liver health, stimulate immunity and help normalize cholesterol levels. In a study from France’s INSERM (National Institute of Health and Medical Research) (Cara et al. 1992) researchers found that WGA-containing wheat germ reduced triglycerides, improving cardiovascular health.
The Mayo Clinic had this to say about wheat germ in a slideshow of “10 great health foods:”
“Wheat germ is the part of the grain that’s responsible for the development and growth of the new plant sprout. Although only a small part, the germ contains many nutrients. It’s an excellent source of thiamin and a good source of folate, magnesium, phosphorus and zinc. The germ also contains protein, fiber and some fat. Try sprinkling some on your hot or cold cereal.”
Probiotics break down lectins in the gut
Some plant lectins are extremely beneficial for our health. They boost our immunity and offer untold metabolic benefits. Other plant lectins need to be broken down in the gut, and as they are, they are neutralized.
In a 2017 study from Argentina’s National University of Tucumán, researchers tested WGA lectin consumption in poultry together with probiotic testing. The research found that certain strains of probiotics successfully break down WGA within the gut. The researchers utilized poultry being fed with a mono-diet (wheat).
The researchers tested 14 intestinal probiotics against the lectin. They found that 9 of the Lactobacillus strains and one Enterococcus strain played a role in the breakdown of this lectin.
Furthermore, they found that cultured probiotics significantly broke down the lectin when they were exposed to the probiotics prior to contact with the intestinal cells.
This, precisely, is what occurs in a healthy gut.
As expected, the study found that some strains were more effective than others. Species such as L. salivarius and L. reuteri were most effective and more efficient at protecting the intestinal walls from exposure to undigested WGA lectins.
Note that poultry farmers often feed their birds with significant antibiotics, which deter the growth of good probiotic populations. This produces a lack of the very probiotics the birds need to digest their wheat feed.
Modern humans also face this problem
Humans face a similar problem, because so many antibiotics are being prescribed without warrant. These have the effect of killing off the very probiotics we need to break down lectins before our intestinal walls are exposed to them.
Of course, before the mass prescribing of antibiotics, our intestinal tracts were much more healthy and able to break down unneeded lectins and so many other potentially allergenic food compounds. This is why food allergies and other sensitivities have been growing exponentially in modern times.
As I show in my book on probiotics, many other studies have shown that probiotics also help protect the health of the intestinal wall in many other ways.
And my book on leaky gut syndrome shows how a healthy diet with good cultured foods and probiotic supplements can prevent leaky gut syndrome.
The bottom line: Go ahead and eat whole, healthy plant-based foods without worrying about lectins or glutens. Just make sure your intestinal tract is teeming with good populations of probiotics to digest them – as was intended by Mother Nature.
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For other references (in parentheses) see:
Adams, C. The Gluten Cure: Scientifically Proven Natural Solutions to Celiac Disease and Gluten Sensitivities. Logical Books, 2015.
