Digestion time varies among individuals and between men and women. After you eat, it takes about six to eight hours for food to pass through your stomach and small intestine. Food then enters your large intestine (colon) for further digestion, absorption of water and, finally, elimination of undigested food. It takes about 36 hours for food to move through the entire colon. All in all, the whole process — from the time you swallow food to the time it leaves your body as feces — takes about two to five days, depending on the individual.
A great way to figure out your transit time is to eat pigmented food like beets or homemade charcoal containing ice cream.
Your digestive system is designed to give you feedback. Experiences like bloating, upset stomach, diarrhea, and gas are just a few ways that your body “talks” to you about what’s going on as you digest.
What determines how fast or how slow transit time is? To answer that question, it’s helpful to understand the mechanism by which your gut bacteria impact transit time. Gut bacteria tend to use carbohydrates as a primary source of energy. As they consume these carbohydrates, they create beneficial byproducts (i.e., metabolites), that not only influence transit time, but support and strengthen the gut barrier and help support the immune system.
With a slow transit time, bacteria may be deprived of carbohydrates to consume and start to feed on protein instead. Byproducts made from the breakdown of protein, such as ammonia and sulfur compounds, can have harmful effects on gut and metabolic health—for example, increased mucosal damage, disruption of colon cell tight junctions, and increased inflammatory response. (It’s also worth noting that the slower material passes through the colon, the more water is drawn from stool, which makes it harder to pass and can cause issues like constipation.)
On the other hand, if food passes through too quickly and transit time is relatively fast, you may not absorb the optimal amount of nutrients. This, along with dehydration, is one of the main concerns with a chronic fast transit time. Digested food material needs to spend enough time in the GI tract to absorb water and nutrients properly. Certain health conditions can also result in a faster-than-average transit time, such as food allergies and intolerances, anxiety, celiac disease, and inflammatory bowel disease.
At the end of the day, transit time is just one piece of information if you’re investigating your bowel movements. Other information could include:
- is poop getting stuck. Are you completely emptying?
- gut microbiome health. Do you experience bloat/gas with meals or even when you haven't eaten?
- Do you need to support digestion? Having trouble digesting fats, proteins or carbs?
What do you think your transit time is? How can you impact your gut health?
Do you experience bloat and other digestive concerns...
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