Proteins Found in Meat and Milk Inhibit Growth of Small Intestinal Tumors

Immune-stimulating food components, particularly proteins found in milk, play a crucial role in preventing tumor growth in the small intestineImage Julio Melanda / Pexels 

A research team led by Hiroshi Ono from the RIKEN Center for Integrative Medical Sciences in Japan has made a significant discovery regarding the immune-boosting properties of dietary proteins. The study revealed that certain food components, particularly proteins found in milk, play a crucial role in preventing tumor growth in the small intestine. These findings, published in Frontiers in Immunology on September 18, 2024, open new avenues for dietary interventions in cancer prevention.

Immune-Stimulating Food Components

Immune-stimulating food components, also known as dietary antigens, are typically associated with triggering allergic reactions to foods such as peanuts, shellfish, wheat, eggs, and milk. Even when not causing allergic responses, these antigens, along with others present in plants and legumes, are still recognized as foreign by the immune system. This recognition prompts the body to mount a defense.

Previous studies by Ono's team revealed that dietary antigens activate immune cells specifically in the small intestine, unlike the colon. At the same time, it is known that certain immune cells activated by gut bacteria can suppress tumors in the intestines. By connecting these two insights, the researchers aimed to determine if dietary antigens could suppress tumor formation in the small intestine.

Testing the Hypothesis

The team began their experiments using a unique breed of mice with a mutation in a tumor-suppressing gene. This mutation mirrors what occurs in humans with familial adenomatous polyposis (FAP), a genetic disorder that increases the risk of cancer. In FAP, hundreds to thousands of precancerous polyps (adenomas) form in the colon and rectum, and without treatment, these individuals are likely to develop colon and/or rectal cancer at an early age.

In the first experiment, the researchers fed the mice either a standard diet or an antigen-free diet. They found that the mice consuming the standard diet developed fewer tumors in the small intestine but showed the same number of tumors in the colon as those on the antigen-free diet. 

To further understand this, the researchers added a common antigen, albumin—found in meat—to the antigen-free diet. They ensured the total protein content was the same as that in the standard diet. The results showed that mice fed this diet exhibited tumor suppression in the small intestine, just as with the standard diet. This indicates that the presence of dietary antigens, not the nutritional value or a specific antigen, was directly linked to inhibiting tumor growth.

Immune Cell Response

In addition to tumor suppression, the three diets affected immune cells in the small intestine, particularly T cells. Mice on the antigen-free diet had significantly fewer T cells compared to those on either the standard diet or the antigen-free diet with added albumin. Further experiments revealed the biological mechanisms behind these immune responses.

Therapeutic Applications and Risks

These findings have potential therapeutic applications, particularly for individuals with intestinal diseases. Antigen-free diets, which consist of simple amino acids without proteins, are similar to those given to patients with severe digestive conditions like Crohn’s disease or irritable bowel syndrome. Such diets are designed to reduce the digestive burden and may be helpful for individuals with acute intestinal issues.

However, Ono warns that "small intestinal tumors are far less common than those affecting the colon, but the risk is higher in cases of familial adenomatous polyposis. Therefore, careful consideration must be given when using elemental diets to treat inflammatory bowel diseases or other intestinal conditions in these patients." 

Elemental diets, which are sometimes followed by people without severe intestinal conditions or allergies as a method to lose weight or reduce bloating and inflammation, could pose risks. The study’s results suggest that these diets may be harmful and should not be adopted without medical supervision.

This groundbreaking research provides valuable insights into the relationship between dietary proteins and tumor growth in the intestines. By demonstrating the role of immune-stimulating food components in inhibiting small intestinal tumors, this study highlights the potential of tailored diets for cancer prevention and treatment. However, caution is necessary, as restrictive diets can have unintended consequences if not used appropriately under medical guidance.

These findings contribute to the growing understanding of how nutrition interacts with the immune system and could shape future approaches to managing intestinal diseases and cancer prevention strategies.

Summary:

Tumor Suppression in the Gut via Food Proteins

Researchers at RIKEN Center have found that food proteins, particularly from milk, can inhibit tumor growth in the small intestines. Their study showed that mice fed normal diets had fewer tumors compared to those on antigen-free diets. Introducing albumin, a common protein, to the antigen-free diet similarly suppressed tumors, indicating the tumor suppression is linked to the presence of antigens rather than nutritional value. The findings have implications for clinical diets, suggesting caution in using elemental diets for gastrointestinal issues without medical supervision, as they may pose risks if not carefully considered.

References:

* Eurk Alert, Proteins in meat, milk, and other foods suppress gut tumors

* Frontiers in Immunology , Food antigens suppress small intestinal tumorigenesis