A research team led by Hiroshi Ohno at the RIKEN Center for Integrative Medical Sciences (IMS) in Japan has found that food antigens, such as proteins in milk, play a role in preventing tumor growth in the small intestine. Their experiments demonstrated how these proteins stimulate the intestinal immune system, helping to halt the formation of new tumors. The results of this study were published in the scientific journal Frontiers in Immunology on September 18.
Food antigens often receive negative attention due to their link with allergic reactions to various foods, including peanuts, shellfish, bread, eggs, and milk. Even in cases where they don’t cause allergies, these antigens—along with others found in plants and beans—are still treated as foreign elements that the immune system must address. Previously, Ohno and his team have shown that food antigens can activate immune cells specifically in the small intestine, but not in the larger intestine. Additionally, some immune cells activated by gut bacteria are known to play a role in tumor suppression. The latest study aimed to combine these ideas and investigate if food antigens can indeed inhibit tumors in the small intestine.
The researchers used a unique strain of mice that had a genetic mutation affecting a tumor-suppressing gene. Similar to individuals with familial adenomatous polyposis, these mice develop tumors throughout their small and large intestines. In an initial experiment, they provided these mice with either a standard diet or a diet free of antigens. The results showed that the mice receiving the standard diet had significantly fewer tumors in their small intestines, while the number of tumors in the large intestine remained the same.
Following that, the researchers supplemented the antigen-free diet with a commonly known antigen called albumin, found in meat, ensuring the total protein content matched that of the standard diet. When the mice received this modified diet, the tumors in the small intestine were suppressed in the same way as observed with the normal diet. This suggests that the tumor suppression effect is directly linked to the presence of the antigen, not merely the nutritional components of the food.
The different diets also had an impact on immune cells, particularly T cells, in the small intestine. Mice consuming the basic antigen-free diet exhibited a significant reduction in T cell numbers compared to those on a standard diet or the antigen-free diet enriched with milk protein. Further experimentation shed light on the biological mechanisms behind this effect.
The insights gained from this study carry significant clinical implications. Elemental diets, similar to the antigen-free diets used in this research, consist of simple amino acids without full proteins. This reduces the digestive burden and can be beneficial for individuals with serious gastrointestinal issues like Crohn’s disease or irritable bowel syndrome. Ohno noted that “small intestinal tumors are much less common than those in the colon, but the risk is increased in those with familial adenomatous polyposis, so the use of elemental diets for managing inflammatory bowel disease or other gastrointestinal disorders in these patients should be approached with great caution.”
Furthermore, elemental diets are sometimes adopted by healthy individuals keen on losing weight or alleviating bloating and inflammation. However, the new findings indicate that such practices could pose risks and highlight the importance of consulting a healthcare professional before starting these diets.
