Antinutrients and IBS


  • Antinutrients are any compounds that damage the gut wall and interfere with the absorption of nutrients by blocking enzymes
  • Antinutrients are bioactive dietary peptides (protein fragments) commonly found in grains, legumes, dairy, nuts and potato (a nightshade)
  • The worst antinutrient is wheat but any antinutrient that can damage your gut wall is toxic
  • If you are genetically susceptible to antinutrients, the proteins from these foods can damage the intestinal lining of your gut, causing Leaky Gut (intestinal permeability)
  • The only IBS diet that specifically targets antinutrients is the Paleo Autoimmune Diet.

NB: The FODMAP diet targets complex sugars only (carbohydrates) and ignores antinutrients in protein foods.The specific Carbohydrate diet targets starches only.

Most IBS diets exclude grains, but often for different reasons. The FODMAP diet for example disallows wheat for its sugars (fructans) but allows other toxic grains such as brown rice.

  • IBS / gut inflammation can be caused by both maldigested sugars as well as protein-based antinutrients
  • The only diet that specifically targets antinutrients is the Paleo Autoimmune Diet
  • Vegetables and fruit generally have low levels of antinutrients, with the exception of nightshades such as white potato. There are several theories on the toxicity of tomato and eggplant as their levels of lectins aren’t known.

Leaky Gut (intestinal permeability)

Food is digested through the enterocytes – cells that line the gut wall. Only nutrients (micro molecules) should cross the gut wall. If the enterocytes are damaged or if the proteins that form tight bonds between the cells are damaged then incompletely undigested protein fragments can “leak” through the gut and into the blood stream. The innate immune cells of the gut, the white blood cells,  see these peptides as invaders and launch an attack against them. This is the process of Leaky Gut (intestinal permeability) which over time can lead to autoimmune disease for those who are genetically susceptible.

Pathogens such as E.coli can also leak into the blood stream.

Antinutrients are any compounds that interfere with the absorption of nutrients. The worst antinutrients can directly interact with and damage the gut wall, causing intestinal permeability (Leaky Gut) and also help to cause an immune reaction. IBS is believed to be a low-level form of autoimmune disease such as Celiac Disease or Crohn’s Disease. Some antinutrients also inhibit digestive enzymes, making them harder to digest, which in turn can lead to bacterial dysbiosis.

 A list of the Antinutrients


Lectins are sugar-binding proteins and are present in all plant foods. Lectins are concentrated in the seeds of plants. The worst proinflammatory lectins are in grains (all grains) and legumes (dried beans – all types). These foods are essentially seeds. Grains are grass seeds; dried beans are legume seeds and nuts are tree seeds. Nature devised lectins to protect the seed from digestion and to cause gastrointestinal damage to anything that eats it, including us. Lectins are highly toxic uncooked and while soaking and cooking reduces lectin content this doesn’t completely eradicate it.

The worst lectins are prolamines (e.g. Gluten) and agglutinins (wheat germ agglutinin WGA).

Lectins can cause gut inflammation because lectins bind to sugar molecules, and our intestines are lined with carbohydrate molecules, so lectins can bind to the microvilli lining our intestine, causing damage. Lectins can also force through the gaps between the epithelial cells lining the intestine and into the blood stream. Our innate immune system recognises certain amino acid shapes from these lectins as pathogenic, and will mount a defence against these proteins. This is how Leaky Gut (intestinal permeability) develops.

Not all lectins gain entry to the gut barrier, but once they do, the protein fragments can set up an immune reaction, causing gut inflammation.

The lectin Gluten is the prime cause of Celiac Disease, one of the most well known of the autoimmune diseases.

Lectins are largely indigestible and a considerable portion of foods high in lectin will pass through unabsorbed. These food fragments can not only feed bacteria, but in the case of Leaky Gut can penetrate the gut wall and enter the blood stream, causing inflammation and possibly an immune reaction.

Generally, the lectins in vegetables are safe. There are a few exceptions – the nightshades white potato, tomato and eggplant for example with potato believed to be the worst.

Soaking, sprouting and cooking removes some, but not all, lectins. And some people are more sensitive to lectins than others because some of us have a genetic susceptibility to lectin intolerance.

While all plants contain lectins the most potent lectins are the prolamines and agglutinins.

Food sources of prolamines are wheat (gliadin), barley (hordein), rye (secalin), corn (zein) and oats (avenin).

Food sources of agglutinins are wheat (WGA), potato (STA: Solanum tuberosum agglutinin), kidney beans, peanuts, nuts, soy beans and lentils.

Phytic Acids (phytates)

Phytates are the storage system of phosphorus, largely in seeds. Phytates are indigestible as we lack the enzyme to digest them. Phytic acid is in the hulls of nuts, seeds and grains. Phytates bind with essential minerals and prevent their absorption. Phytates inhibits enzymes that digest our food, such as pepsin and Trypsin for protein and amylase for converting starch to sugar. Nuts and seeds have the highest proportion of phytates, in some cases much higher than grains and legumes.

Phytic acid not only grabs on to or chelates important minerals, but also inhibits enzymes that we need to digest our food, including pepsin, needed for the breakdown of proteins in the stomach, and amylase, needed for the breakdown of starch into sugar. Trypsin, needed for protein digestion in the small intestine, is also inhibited by phytates.


Saponins are antinutrients and are concentrated in the seed of the plant. Saponins are basically detergents that protect the plant from consumption by attacking enterocytes, the cells that line the gut wall. Saponins can interact with and damage cell membranes in the lining of the gut. This leads to gut impermeability (Leaky Gut) as these “holes” in the gut wall allow particles of food through, causing inflammation and possibly an immune reaction.

The worst saponins are in legumes and pseudo-grains (buckwheat, quinoa, amaranth) and nightshades such as potato (glycoalkaloids). Gut cells that have been damaged by saponins are unable to transport nutrients. If saponins enter the blood stream they can destroy red blood cells. Saponins are adjuvants, meaning they affect the immune system leading to pro-inflammatory cytokine production causing the creation of antibodies – the forerunner of autoimmune disease.


There aren’t meany studies on dairy peptides and their relation to gut permeability. It’s not known whether or not casomorphins can get into the blood stream as do other antinutrients. Casomorphins are peptides derived from the milk protein, Casein. Casomorphins have a mild opiate effect as they are a low-level morphine, and are therefore constipating.


How fibre fights inflammation

Fibre offers a substrate (food) for good bacteria. Bacteria ferment dietary fibre and the short chain fatty acids and hydrogen gas all makes the pH of your colon more acidic. Pathogens are pH sensitive and can’t survive in an acidic environment. People with IBS often believe fibre is a problem food and can’t eat vegetables. This often means that in lieu of fibre they’re eating grains, breads etc which causes Leaky Gut and feeds pathogenic bacteria.

When bacteria are starved of fibre, they can eat the mucous lining of the gut, which can help to cause Leaky Gut. This could also be a cause of ulcerative colitis.

A low fibre intake can therefore lead to increased gut permeability.


Lipopolysaccharides (LPS) or endotoxins, are large molecules found in the outer membrane of gram negative bacteria. These can leak from the gut into the blood stream, leading to inflammation. A Leaky Gut can be exacerbated by a low fibre diet that encourages pathogenic growth.