When bowel habits change, many people first notice how often they go—or don’t. Coffee, fatty foods, and large meals can all influence bowel movement frequency through well-known digestive pathways. However, emerging research suggests that our genes—and possibly our vitamin B1 status—may also play a role.
Among the most intriguing findings was that two of the strongest genetic signals were linked to how the body processes vitamin B1, also known as thiamine.
How Thiamine Affects Bowel Movement
Researchers analyzed genetic data alongside self-reported stool frequency from people of East Asian and European ancestry. In a subset of participants who also provided dietary data, including thiamine intake, higher thiamine intake from food was associated with more frequent bowel movements.
Thiamine’s role in energy metabolism has long been established. It helps the body convert the food we eat into usable energy—a function especially important in the gut, where muscle contractions occur continuously, and the intestinal lining renews itself every three to five days.
However, thiamine does more than fuel cells—it also helps nerves communicate. In the gut, nerves in the intestinal wall sense when food stretches the intestine and trigger a wave-like muscle movement—called peristalsis—that pushes food along. Peristalsis depends on acetylcholine, a chemical messenger that tells gut muscles when to contract, and thiamine is needed to make it.
When thiamine levels drop, gut cells can’t produce enough energy, impairing neural signaling and weakening muscle contractions, ultimately slowing intestinal transit.
“Intestinal motility appears to be a heritable trait,” D’Amato said, noting that some people may be genetically predisposed to slower gut movement. “The vitamin B1 we consume may be more effective in some individuals than others because of their genetic profiles.”
The study identified two genes—SLC35F3 and XPR1—involved in transporting and activating thiamine within cells. Notably, the association between dietary thiamine intake and bowel movement frequency varied depending on genetic differences in these pathways.
Evidence Links Vitamin B1 to Constipation
Beyond genetic data, other research offers supporting evidence.
These effects persisted even after accounting for fiber intake, other B vitamins, and overall caloric intake, suggesting that thiamine may influence gut motility through mechanisms beyond general nutritional status.
How Thiamine Strengthens Your Gut
Thiamine’s role in gut health extends beyond motility.
Gut bacteria require thiamine to help break down food into butyrate, a beneficial metabolite that strengthens the gut barrier, supports healthy motility, and serves as a key energy source for colon cells.
When thiamine levels are low, gut cells struggle to make enough energy to function properly, Kara Siedman, a registered dietitian and director of partnerships at Resbiotic Nutrition, told The Epoch Times. The energy shortage is especially problematic for intestinal cells, which are highly energy-dependent and must constantly renew themselves while maintaining the gut’s protective barrier.
“When energy (ATP) availability is compromised, the gut barrier can become more permeable, allowing bacterial components to cross into circulation and interact with the immune system,” Siedman said, adding that thiamine deficiency can affect not just bowel movement speed, but overall gut barrier health and microbial balance.
Should You Take Thiamine Supplements?
True thiamine deficiency is uncommon in healthy people eating a varied diet. The recommended daily allowance (RDA) for thiamine, meant to prevent deficiency in most healthy people, is about 1.1 to 1.2 milligrams per day—an amount easily obtained through a varied diet including whole grains, cereals, legumes, and pork.
“The average healthy individual who eats a varied diet is unlikely to have thiamine deficiency,” Dr. Adam Pont, a board-certified gastroenterologist with Medical Offices of Manhattan and contributor to LabFinder, told The Epoch Times, adding that the average Western diet usually contains sufficient thiamine to avoid deficiencies.
However, some groups of people are more vulnerable to thiamine insufficiency. Siedman noted that populations at a higher risk for deficiencies include those with chronic alcohol use, those taking loop diuretics, those who have undergone bariatric surgery, older adults with low or inadequate dietary intake, people with diabetes, those who rely heavily on highly processed foods, and those experiencing prolonged vomiting, malabsorption, or restrictive eating patterns.
“In these groups, assessing dietary intake and considering supplementation may be an important part of a comprehensive approach to metabolic and gastrointestinal health,” Siedman said.
For people with chronic constipation, IBS, or unexplained digestive symptoms, experts emphasize medical evaluation rather than self-treatment. Supplementation should ideally be guided by a health care professional, particularly if a deficiency is suspected.
Over-the-counter thiamine is most commonly found in multivitamins or B-complex supplements, with most providing about 1.5 mg, roughly matching daily needs.
While genetics may influence how strongly vitamin B1 affects bowel habits, getting enough thiamine through food—or a standard multivitamin—may help keep things moving, whether or not someone wins the genetic lottery.
