What Are Amylase Trypsin Inhibitors and Their Effects?

Amylase trypsin inhibitors, or ATIs, are proteins found naturally in many common plant-based foods. While they serve a protective purpose for the plant, they have gained attention for their potential effects on human digestion and health. These compounds can influence how the body processes certain nutrients and may be connected to digestive discomfort in some individuals.

Defining Amylase Trypsin Inhibitors

Amylase trypsin inhibitors are proteins in the seeds of many cereal grains that are part of the plant’s innate defense system, protecting it from pests and pathogens. Their name reflects their function: they inhibit the action of amylase, which breaks down starches, and trypsin, which digests proteins. This interference with digestion serves as a deterrent to insects and other predators.

These inhibitor proteins are stored in high concentrations within the endosperm, the starchy tissue that provides nutrients for the developing plant embryo. In wheat, ATIs are categorized into several groups based on their molecular structure, including monomeric (single-unit), dimeric (two-unit), and tetrameric (four-unit) forms. This structural variety influences how they interact with enzymes in the digestive tract.

Common Dietary Sources of ATIs

Amylase trypsin inhibitors are present in all cereal grains, but their concentration is particularly notable in wheat, barley, and rye. Consequently, food products made from these grains, such as breads, pastas, cereals, and baked goods, are significant dietary sources of ATIs. Wheat is an especially prominent source in many global diets.

Modern wheat varieties, particularly the most commonly cultivated types, tend to have high levels of ATI activity. Factors such as the specific genotype of the wheat and the environmental conditions in which it is grown can influence the final concentration of these proteins. While most attention is given to wheat, ATIs are also found in other grains like maize and rice, and legumes also contain these inhibitors.

How ATIs Affect Digestion

The primary action of ATIs in the human body is direct interference with nutrient breakdown. These proteins are resistant to digestion and travel intact into the small intestine. There, they bind to and deactivate digestive enzymes, disrupting the normal process.

Specifically, ATIs block alpha-amylase, an enzyme in saliva and pancreatic secretions responsible for breaking down complex carbohydrates. This inhibition slows the conversion of starch into smaller, absorbable sugar molecules. The result is that more undigested starch may pass from the small intestine into the large intestine.

Simultaneously, ATIs inhibit proteases like trypsin and chymotrypsin, which are needed to break down proteins into amino acids. By binding to these enzymes, ATIs lead to incomplete protein digestion, meaning fewer amino acids are available for absorption. This combination of impaired starch and protein digestion can reduce the nutritional value obtained from a meal.

Broader Health Implications of ATIs

The influence of ATIs extends beyond digestion and can involve the immune system. Wheat ATIs are recognized for their ability to stimulate innate immune responses within the gut. They achieve this by interacting with a specific protein receptor on the surface of immune cells called Toll-like receptor 4 (TLR4), a component of the body’s first-line defense system designed to recognize threats.

Activation of TLR4 by ATIs triggers a cascade of inflammatory signals in the gut lining, contributing to a state of low-grade inflammation. For some individuals, this inflammatory response can manifest as digestive symptoms such as bloating, gas, and abdominal pain, which are characteristic of non-celiac wheat sensitivity (NCWS). ATIs are now considered a primary trigger for symptoms in many people with NCWS, separate from the effects of gluten.

This ATI-driven inflammation may also play a role in other conditions. In celiac disease, while gluten is the primary trigger, ATIs are thought to exacerbate the underlying autoimmune response by amplifying intestinal inflammation. By promoting inflammation, ATIs might compromise the integrity of the gut barrier, leading to increased intestinal permeability, sometimes referred to as “leaky gut.” This could allow other substances to pass from the intestine into the bloodstream.

Managing ATI Exposure Through Food Preparation

The activity of amylase trypsin inhibitors in food can be significantly reduced through various preparation and processing techniques. Heat is one of the most effective methods for deactivating these proteins. Thorough cooking of grains and flours can denature the ATI proteins, changing their shape and rendering them unable to bind to digestive enzymes.

Fermentation is another highly effective strategy, particularly the traditional sourdough method for making bread. The long fermentation process, which utilizes both yeast and lactic acid bacteria, breaks down carbohydrates and proteins in the flour, including ATIs. Studies have shown that sourdough fermentation can degrade a significant portion of the ATIs present in wheat flour, reducing their inflammatory potential.

Other methods like soaking and sprouting grains and legumes before cooking can also help diminish ATI activity. These processes initiate the grain’s natural germination, which activates enzymes within the grain that begin to break down storage proteins like ATIs. The extent of ATI reduction can vary based on the duration of the process and the specific grain used.