When they crunched the data, the researchers were able to locate three genetic variants that influence gut motility: rs12407945 in European participants, and rs2581260 and rs12022782 in the multi-ancestry analysis. But they also found that two of the variants influence the activation of B1 and its transport around the body.

In a follow-up analysis of nearly 98,500 people who participated in the UK Biobank, the research team found a strong link between how much vitamin B1 people took in and how often they pooped, suggesting that vitamin B1 helped people go No.2.

The researchers wrote in the conclusion that this is a “previously unrecognized role for vitamin B1.”

There are a few theories on why B1 helps you poop.

Technically, the study just found a link between vitamin B1, aka thiamine, and pooping frequency—it didn’t explore the exact reason behind this. “We still do not know the exact mechanisms,” Mauro D’Amato, PhD, study co-author and professor of Medical Genetics at LUM University, tells SELF. But doctors say there may be something to this.

“Vitamin B1 may improve intestinal motility by supporting the production of acetylcholine, a neurotransmitter that stimulates contractions in the gastrointestinal system,” Marie Borum, MD, MPH, director of the Division of Gastroenterology at GW Medical Faculty Associates, tells SELF.

Vitamin B1 is also essential for cellular energy production, Jeremy Polman, DO, gastroenterology fellow at Northwell’s Lenox Hill Hospital, tells SELF. “If these utilization pathways are under-active, this could theoretically slow down gut motility,” he says. Some research even suggests that vitamin B1 may also help to soften poop, making it easier to pass.

The link between vitamin B1 and pooping isn’t entirely new. A study published in the journal BMC Gastroenterology in 2024 analyzed data from more than 10,000 people, including 1,123 that had chronic constipation. The researchers discovered that those who increased their intake of vitamin B1 had a lower risk of being constipated in the future.

Because of this growing link, “some people will use vitamin B1 for IBS with constipation,” Rudolph Bedford, MD, gastroenterologist at Providence Saint John’s Health Center in Santa Monica, CA, tells SELF. (However, it’s not considered one of the main treatments for this form of IBS, he adds.)

You can get vitamin B1 from foods or supplements.

Vitamin B1 is a water soluble B vitamin that’s naturally present in some foods and added to others. Most adults need to take in 1.1 to 1.4 milligrams a day of the vitamin, according to the National Institutes of Health (NIH). You can get vitamin B1 from a range of foods, including:
Fortified breakfast cereals (1.2 milligrams)

  • Egg noodles (0.5 milligrams)
  • Pork chop (0.4 milligrams)
  • Trout (0.4 milligrams)
  • Black beans (0.4 milligrams)

There are a few things to try if you’re struggling with constipation.

While taking vitamin B1 may help with constipation, doctors say more work is needed. “We are not there yet,” Dr. D’Amato says. “However, our results definitely point to vitamin B1 as a possible regulator of intestinal motility.” This includes having vitamin B1 in your diet or as a supplement, he says.

Still, doctors need more information on specific situations when you should take vitamin B1 and how much of it you should have, Dr. Borum says.

For now, Dr. Bedford recommends that you have foods naturally high in fiber like beans, broccoli, and fruits, along with “plenty of water” to try to get your GI tract moving when you’re constipated. (Women under 50 should try to get at least 25 grams of fiber per day, according to the National Academy of Medicine.) Ramping up your level of activity and exercise may also help, according to Dr. Borum.

But if you’ve tried that and you’ve been struggling for a week or more, or you’re in pain, Dr. Bedford says it’s time to talk to a healthcare provider. “A physician will come up with some mechanism of treatment, whether it’s through nutrition or medication,” he says.