Researchers led by Hiroshi Ohno at the RIKEN Center for Integrative Medical Sciences in Japan have made an important discovery about how food antigens, like albumin found in common foods such as milk and meat, may play a vital role in preventing tumors from forming in the small intestine. This research, published in Frontiers in Immunology, provides new insights into how the immune system in the gut responds to certain proteins from our diet, offering hope for better understanding cancer prevention in this delicate region of the body.

To understand this breakthrough, it’s essential to grasp what food antigens are and how they typically interact with the human body. Food antigens are proteins that the immune system recognizes as foreign and potentially harmful, even though they are not necessarily dangerous on their own. For example, the proteins in peanuts, shellfish, or milk can sometimes trigger allergic reactions, ranging from mild symptoms to life-threatening conditions. Even when allergic reactions don’t occur, the immune system often scrutinizes these antigens, keeping them under surveillance as potential threats. Traditionally, food antigens are viewed with some level of caution, due to their role in allergies, but the new research from Ohno’s team paints a more complex picture of their function, particularly in the small intestine.

The small intestine plays a critical role in absorbing nutrients from food, but it is also home to a large portion of the body’s immune cells, including T cells, which help the body identify and attack harmful invaders. In previous research, Ohno and his team had shown that food antigens activate immune cells in the small intestine, but not in the large intestine. This raised an interesting question: Could food antigens also be involved in protecting the gut from diseases like cancer?

To answer this question, the researchers turned to a specialized type of mouse that has a genetic mutation affecting the tumor-suppressing gene. This mutation is similar to one found in humans with familial adenomatous polyposis, a condition that leads to the development of numerous tumors in both the small and large intestines. These mice provided a good model for studying how food antigens might influence the formation of intestinal tumors.

The researchers divided the mice into three groups, each receiving a different diet. One group was fed normal food, which contained a variety of antigens from plants and animal products. A second group received antigen-free food, which was designed to avoid any proteins that might trigger an immune response. Finally, a third group of mice was fed antigen-free food, but with a specific antigen added to the mix: albumin, a common protein found in animal products like meat and eggs. Importantly, the amount of protein in the diet was kept consistent across all groups, ensuring that any effects observed were due to the presence of the antigen, not differences in nutrition.

The results were striking. Mice that ate normal food or the antigen-free food with added albumin developed significantly fewer tumors in the small intestine compared to those that received only antigen-free food. However, the number of tumors in the large intestine was the same across all groups, suggesting that the effect of food antigens was specific to the small intestine. This was a crucial finding because it indicated that the antigens were not just affecting the overall health of the mice, but were actively engaging the immune system to prevent tumors from developing in a specific part of the gut.

But how exactly did the antigens accomplish this? The researchers found that the presence of food antigens stimulated the production of T cells in the small intestine. These immune cells are known to play a key role in identifying and destroying abnormal or cancerous cells, and the increase in their numbers was likely responsible for the reduction in tumor formation. Mice that were fed the antigen-free diet, on the other hand, had far fewer T cells in their small intestines, leaving them more vulnerable to tumor growth.

The implications of these findings are significant, especially for people who rely on specialized diets for medical reasons. Elemental diets, which consist only of simple amino acids rather than whole proteins, are often prescribed for patients with severe gastrointestinal conditions like Crohn’s disease or irritable bowel syndrome. These diets are designed to be easy to digest and reduce inflammation in the gut, but they also eliminate food antigens. Based on the findings of this study, eliminating antigens from the diet could unintentionally reduce the body’s natural ability to suppress tumors in the small intestine, particularly in individuals who are already at higher risk due to genetic conditions like familial adenomatous polyposis.

According to Ohno, “small intestinal tumors are much rarer than those in the colon, but the risk is higher in cases of familial adenomatous polyposis, and therefore the clinical use of elemental diets to treat inflammatory bowel disease or other gastrointestinal conditions in these patients should be considered very carefully.” This highlights the delicate balance that must be maintained when choosing dietary treatments for individuals with complex medical conditions. While elemental diets can be life-saving for some patients, they may carry unforeseen risks, particularly when it comes to tumor formation in the small intestine.

The findings from this study also raise broader questions about the role of diet and the immune system in cancer prevention. While much of the focus on food antigens has been on their potential to cause harm, these results suggest that they may also have important protective functions, at least in certain parts of the body. Further research will be needed to fully understand how different types of food antigens affect the immune system and how this knowledge can be applied to improve health outcomes.

In conclusion, this study provides a new perspective on how food antigens interact with the immune system in the small intestine, offering insights into potential strategies for preventing cancer in the gut. While there is still much to learn, these findings highlight the importance of considering both the benefits and risks of dietary choices, particularly for individuals with genetic predispositions to intestinal cancer. As research continues to explore the complex relationship between diet, the immune system, and cancer, this study opens the door to new possibilities for preventing and treating tumors in the small intestine.

Sources:
https://www.sciencedaily.com/releases/2024/09/240918124955.htm
https://muschealth.org/medical-services/ddc/patients/digestive-diseases/small-intestine/tumors-of-the-small-intestine
https://www.davita.com/diet-nutrition/articles/basics/what-is-albumin