Can Vitamin B1 Help Constipation? A Look at the Latest Research

You inherit many things from your parents: your blood type, eye color, and maybe an aversion to bitter foods. But what about how often you go to the bathroom?

A recent study in Gut highlights a potential link between how often you have a bowel movement (i.e. stool frequency) and your genes. Dr. Díaz-Muñoz and colleagues collected questionnaire data from almost 269,000 people of European and East Asian ancestry who self-reported how often they had a bowel movement.

How often you poop might not seem like the most clinically pressing information to ask over 250,000 participants, but it is an easily measurable trait that serves as a proxy for gut motility — important for people with gastrointestinal disorders like irritable bowel syndrome (IBS). In the same way blood pressure and cholesterol levels inform about overall cardiovascular risk, stool frequency can similarly inform patients about gut motility, especially among those with IBS or chronic idiopathic constipation.

To find the genetic roots of this, the researchers ran a genome-wide association study, or GWAS — scanning the genome for common DNA differences that turn up more often in people who go more (or less) frequently. This turned up 10 new locations in the genome linked to stool frequency, almost doubling the number scientists had previously identified.

From there, they focused on the variants most likely to be causing the difference. Two of them pointed to the same unexpected place: how the body processes thiamine, better known as vitamin B1. One gene affects a transporter that shuttles vitamin B1 into cells throughout the body, especially in the brain and gut — the two primary organ systems underlying IBS pathophysiology. The other gene helps convert thiamine into its active, usable form. We primarily obtain thiamine from meat (pork, fish), beans, lentils, and peas. Thiamine is also added to breads, cereals, and other forms of carbohydrates.

In a follow-up analysis, the researchers looked at dietary data in the UK Biobank from almost 100,000 people and found that higher dietary thiamine intake correlated with increased stool frequency. This suggests that vitamin B1 intake may help bowel movements. Bowel motility relies on proper contractions of the muscles in the gut lining, which are controlled by enteric neurons in the gut. These neurons communicate with each other via neurotransmitters, especially acetylcholine, which is regulated by thiamine levels. Thus, this study identifies thiamine as a new modulator of gut motility.

The study quantified stool frequency as partially heritable (ranging from 6 to 7%). That said, genetics are only part of who we are. Diet, lifestyle and psychosocial factors matter tremendously. While this study is groundbreaking for its size and inclusion of individuals of multiple ancestries, it is an observational study. To affirm these results, a study randomizing patients with constipation to diets high in thiamine (or thiamine supplementation) would provide actionable interventions for patients with IBS-C or chronic constipation. Nevertheless, among those of us who tend to run constipated, adding foods with vitamin B1 to aid in gut motility is not a bad place to start.