Could Eating Turkey Ease Colitis?
According to data in mice, extra tryptophan could reduce the risk of future colitis flares.
For people with inflammatory bowel disease like ulcerative colitis, feasting at large holiday meals can be stressful. New research in mice, however, suggests that certain foods — especially those high in tryptophan, like turkey, pork, nuts and seeds — could reduce the risk of a colitis flare. The findings, published in Nature Communications, point to a noninvasive method of improving long-term colitis management, if the results are validated in people.
“Although there are some treatments for ulcerative colitis, not everyone responds to them,” says senior author and immunology researcher Sangwon Kim, PhD. “This disease has a huge impact on quality of life and can lead to cancer.”
Since ulcerative colitis is caused by inflammation of the inner lining of the colon and rectum, Dr. Kim and his colleagues looked for ways to calm the inflamed tissue. They focused on a group of immune cells called T-regulatory (Treg) cells, which can help break the cycle of inflammation. If they could get more Treg cells to the colon, they thought, perhaps they could reduce the inflammation that causes colitis.
Dr. Kim’s team looked into ways to attract the Treg cells and found specific receptors on the surface of Tregs that acted like an address label, helping the cells find their way to the colon. The more of this receptor (called GPR15) the Treg cells had, the more strongly they’re attracted to the colon. So, they searched for molecules that could make Treg cells produce more GPR15 to turn up that attraction. They found that the nutrient tryptophan — or one of the molecules that tryptophan breaks down into — could increase the number of GPR15 receptors on the cell’s surface.
To test whether these molecules could control colitis, the researchers supplemented tryptophan in the diet of mice over a period of two weeks. They saw a doubling in the number of inflammation-suppressing Treg cells in the colon tissue compared to mice that weren’t fed extra tryptophan. Dr. Kim’s team also saw a reduction in colitis symptoms. What’s more, the effects seemed to last for at least a week after tryptophan was removed from the diet. “In human time that might translate to about a month of benefit,” explained Dr. Kim who is also a researcher at the Sidney Kimmel Comprehensive Cancer Center – Jefferson Health.
Interestingly, when tryptophan was given to mice in the middle of a colitis flare, it provided little benefit, suggesting this dietary change might only be effective at preventing future flares rather than treating them.
The next step for the researchers is to test whether these results can be translated to people with colitis. Tryptophan supplementation is considered safe, as long as the dose doesn’t exceed 100 milligrams per day. Using the mouse data as a guide, Dr. Kim expects that 100 milligrams could be enough to see an effect in humans and is planning further testing in clinical trials.
For people with ulcerative colitis, (A) immune cells called T-regulatory cells (Treg) can help break the cycle of inflammation. A homing receptor, called GPR15, can guide Tregs to the colon. (B) After a mouse eats food supplemented with tryptophan, the Tregs respond by generating GPR15 on their surface. (C) GPR15 is like an address label directing the cell to the right zip code. As a result, more Tregs are attracted to the gut lining, almost like a magnet, and end up in the right destination to enter the colon. The mice fed tryptophan for 2 weeks had double the number of Treg cells in the colon and less gut inflammation.