What are Amylase Trypsin Inhibitors (ATIs)?
Amylase trypsin inhibitors, or ATIs, are a class of proteins found in the seeds of many plants, particularly cereals. Their primary function in the plant is to protect against pests and pathogens by inhibiting the digestive enzymes (amylases and trypsins) of insects. In the human diet, they are widely consumed through cereal-based foods. Recent research has shed light on their potential role in various adverse reactions to wheat consumption, including non-celiac wheat sensitivity (NCWS) and exacerbating symptoms in coeliac disease.
Primary Food Sources of Amylase Trypsin Inhibitors
ATIs are most abundant in the water-soluble portion of cereal grains, the albumin fraction. Consequently, foods and products made from these grains are significant dietary sources.
- Wheat: The most prominent source of ATIs in many diets globally. All types of wheat contain these inhibitors, including common bread wheat (hexaploid), durum wheat (tetraploid), and ancient varieties like spelt and emmer. The concentration of ATIs can vary depending on the wheat variety, growing environment, and specific isoform.
- Barley: Another major cereal that contains ATIs structurally similar to those in wheat. Processed barley products, such as beer and malt, will also contain these compounds.
- Rye: This cereal contains dimeric inhibitors homologous to those found in wheat. As with wheat and barley, products made from rye, like rye bread, are sources of ATIs.
- Maize: Also known as corn, maize contains different types of ATIs, though they are part of the same protein family found in other cereals.
- Millet: This group of small-seeded grasses, grown as cereal crops, contains ATIs as part of its defense system.
- Rice: While generally considered a lower-allergen grain, rice also contains ATIs. However, the types and biological activity can differ from those in wheat and related cereals.
Effects of Amylase Trypsin Inhibitors on the Human Body
For most individuals, ATIs are well-tolerated. However, for some, particularly those with pre-existing inflammatory bowel conditions or sensitivities, these proteins can trigger an immune response. ATIs have a compact and stable structure, making them highly resistant to heat and digestion.
- Immune Response: ATIs can activate the innate immune system by stimulating Toll-like Receptor 4 (TLR4), leading to the release of inflammatory cytokines. This inflammatory signal can exacerbate symptoms in susceptible individuals, potentially contributing to conditions like non-celiac wheat sensitivity (NCWS) and inflammatory bowel disease (IBD).
- Digestive Inhibition: By inhibiting digestive enzymes like amylase and trypsin, ATIs can interfere with the proper digestion of carbohydrates and proteins. This incomplete digestion can lead to gastrointestinal symptoms such as bloating and discomfort in sensitive people.
- Allergic Reactions: ATIs have been identified as allergens, especially in occupational respiratory allergies like baker's asthma, caused by inhaling wheat flour dust.
Impact of Food Processing on ATIs
The effects of food processing on ATI content and activity are complex and still under investigation. Some processing methods can reduce ATI activity, while others have a limited effect.
- Heat Treatment: While ATIs are heat-resistant, prolonged or intense heat (as in some baking processes) can lead to denaturation and a reduction in activity, though this is not always consistent.
- Fermentation: Sourdough fermentation, which utilizes specific lactobacilli, can degrade ATIs and reduce their inflammatory potential. This is one reason some people with NCWS may tolerate sourdough wheat products better than conventional bread.
- Digestion: The digestibility of ATIs varies by wheat variety. Some ancient wheat ATIs have shown greater digestibility than those from modern varieties in in-vitro studies, which could influence their immune effects.
Comparison of ATI Levels in Various Cereals
| Cereal Type | Genome (Ploidy Level) | Key ATI Forms | Notes on Activity and Levels |
|---|---|---|---|
| Common Wheat | Hexaploid (AABBDD) | 0.19, 0.28, 0.53, CM-types | Hexaploid wheats generally have the highest ATI inhibitory activities. |
| Durum Wheat | Tetraploid (AABB) | CM-types, 0.28 | CM-type inhibitors are more abundant in tetraploid wheats than hexaploid types. |
| Spelt | Hexaploid (AABBDD) | CM-types, 0.19, 0.28, 0.53 | Similar ATI composition to common wheat; contains potent TLR4 activators. |
| Einkorn | Diploid (AA) | Trypsin inhibitors | Shows the lowest alpha-amylase inhibitory activity but potentially higher trypsin inhibitory activity due to distinct isoforms. |
| Rye | N/A | Dimeric inhibitors, Trypsin inhibitors | Contains inhibitors similar to wheat, but lacks the specific tetrameric forms. |
| Barley | N/A | Monomeric, dimeric, tetrameric | Contains ATIs similar to wheat, with varying inhibitory activity. |
Managing ATI Consumption
For those who suspect they have a sensitivity to amylase trypsin inhibitors, several strategies can help manage symptoms:
- Consider a Low-ATI Diet: Reducing or eliminating the most potent sources, particularly modern wheat varieties, may alleviate symptoms. This is a dietary approach often explored by those with NCWS or IBD.
- Explore Ancient Grains: Certain ancient grains, especially diploid ones like einkorn, may have lower overall ATI concentrations or different ATI profiles that could be better tolerated by some individuals.
- Opt for Processed Foods: Choosing specific types of processed grain products, especially those made with sourdough fermentation, can lower the content and inflammatory potential of ATIs.
- Consult a Professional: A registered dietitian or a gastroenterologist can provide personalized advice and help identify potential dietary triggers and effective management strategies.
For more in-depth scientific literature, resources like the National Institutes of Health (NIH) or Frontiers in Nutrition can be helpful. A relevant paper is available via the National Institutes of Health.
Conclusion
Amylase trypsin inhibitors are a natural component of many staple cereals, including wheat, barley, and rye. While generally benign, they have been identified as potential triggers for innate immune responses and inflammation in susceptible individuals, contributing to conditions like NCWS and IBD. The amount and specific types of ATIs can vary significantly between grain varieties and can be influenced by food processing methods like fermentation. For those experiencing sensitivities, understanding the dietary sources and how processing affects ATIs can be a key step towards better managing symptoms.
