A team of researchers, led by Hiroshi Ono of the RIKEN Center for Integrative Medicine in Japan, has discovered that immune-stimulating food components, such as milk proteins, help prevent the growth of tumors in the small intestine.
Experiments have revealed how these proteins stimulate the immune system in the gut, allowing it to effectively stop the formation of new tumors. The study was published in the scientific journal Frontiers Immunology on September 18.
Immune-boosting food ingredients
Food components that trigger the immune system are known as food antigens and get a bad rap because they are the cause of allergic reactions to foods like peanuts, shellfish, bread, eggs, and milk. Even when they don’t cause an allergic reaction, these antigens—along with many others found in plants and legumes—are still foreign substances that the immune system must recognize.
In previous studies, Ono and his team found that dietary antigens activate immune cells in the small intestine, but not in the large intestine. Meanwhile, some immune cells activated by gut bacteria are known to suppress tumors in the intestine. In the new study, researchers at the RIKEN Center for Integrative Medicine combined these two ideas and tested whether dietary antigens suppress tumors in the small intestine.
The team began their experiment using a special type of mice that had a mutation in a gene that prevents tumors from forming, similar to what happens to people with familial adenomatous polyposis. When this gene is disrupted, tumors develop in the small and large intestines.
Familial adenomatous polyposis (FAAP) is a rare genetic syndrome that increases the risk of developing cancer. This syndrome is characterized by the development of hundreds to thousands of precancerous polyps (adenomas) in the colon and rectum. If left untreated, individuals with FAAP develop colon and/or rectal cancer at a relatively young age.
The first experiment was fairly simple: they fed these mice either regular food or antigen-free food, and found that the mice that received the regular food developed fewer tumors in the small intestine, but the same number in the large intestine.
Next, they added a common antigen called albumin—which can be found in meat—to the antigen-free diet, making sure the total amount of protein was the same as in a normal diet. When the mice were given this diet, tumors in the small intestine were suppressed just as they were with normal food. This means that the tumor suppression was directly linked to the presence of antigens, not to the nutritional value of the food or any particular antigen.
The three diets also affected immune cells, specifically T cells, in the small intestine. Mice fed the antigen-free diet had significantly fewer T cells than those fed normal chow or the antigen-free chow with albumin. Further experiments revealed the biological process that makes this possible.
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These findings suggest therapeutic applications; antigen-free diets are similar to those given to some patients, which include simple amino acids without proteins. This reduces the burden of digestion and could help people with severe intestinal conditions such as Crohn’s disease or irritable bowel syndrome.
“Small intestinal tumors are much less common than those of the colon, but the risk is higher in familial adenomatous polyposis, so the use of elemental diets to treat inflammatory bowel disease or other intestinal conditions in these patients should be carefully considered,” Ono says, according to EurekAlert.
While racist diets are sometimes followed by people without severe intestinal conditions or allergies as a healthy way to lose weight or reduce bloating and inflammation, the new findings suggest they could be dangerous, and stress that these diets should not be used without a medical recommendation.