Large Colon and Ulcerative Colitis

Colon Timing & Digestion

I decided to create a page dedicated to timing and digestion in the large colon for those with Colitis. For many UCers, symptoms are affected by digestion a lot, and the subject is ubiquitous in discussions and forums. Hopefully there's some information below which might help Colitis sufferers learn how, why and when certain symptoms occur.

Timing of the Colon

It's notoriously difficult to work out the timing of an individual's digestive system due to the number of factors that can affect it. I found the only way I was able to discover certain things was to keep an indepth food / symptom / meds diary, and also to stay on the same diet for a long time (months).

The eureka moment came after I'd eaten something that was outside of my strict diet - I had some symptoms 3 days later. This was a surprise because I'd always believed that digestion was a 24 hour cycle - after reading about it, I now realise this is not the case. This discovery provided an answer to some confusing symptoms I'd experienced and also helped me identify some of the culprits in my diet.

So it's worth remembering that this is not an exact science! There are many variables making it impossible to give exact times for each stage of the digestion process, but you might be able to get somewhere close, or at least uncover certain areas that help you. As ever with Colitis, it takes patience along with trial and error.

Average digestion timings

The length of time it takes the average healthy body from eating food to exit of waste from the digestion system can range from 8 hours to 72 hours. That's a huge difference, although the average would be somewhere in the middle.

If you can work out how fast food is going through your system, you might be able to work the dietary cause of some of your colitis symptoms. Fruit and vegetables pass through more quickly than meat.

Food is partially digested in the stomach; begins moving to the small intestine in approximately 1 to 2 hours and takes approximately 4 hours to complete.

I've noticed that between 1.5 to 2 hours after eating, my colon begins to flex and bring any gas through. If your symptoms include painful cramps, this can be when they start as part of the digestion process.

Food moves through (is absorbed by) the small intestine in approximately 2.5 to 4 hours.

In a healthy body, waste takes an average of 40 hours to pass through the large colon (33 hrs for men, 47 hours for women). It's worth noting that these are averages and excluding illness/diarrhea, food can actually pass through the large colon within 6 hours for some. This is why it has taken me so long to discover how long my cycle takes - there are so many variables!!

GI - Timing cycle Large Colon - Timing cycle

Colitis symptoms and eating

Quite a few times I've seen UCers ask whether it's possible to experience symptoms after eating. Interestingly it is, and it's something I only realised after reading about digestion. However, often it's not the food that has just been eaten that is causing symptoms/pains/urgency etc. - it's the mechanism of the GI at work.

The colon responds to certain electrical signals sent when the stomach stretches - the reason the signals are sent is to tell the body to make room for more food. These signals trigger peristalsis (waves) along the colon which can be responsible for the urge to go to toilet.

Of course, in a healthy person this wouldn't normally mean a visit to the toilet, but as we know, for those with IBD it's a different story! Also, in relation to Colitis, where the colon is inflammed in certain areas, it would suggest that the waves could cause cramps (not the food that has just been eaten, which will still be being digested in the stomach).

The electrical activity can start as quickly as 15 minutes after eating and appears to effect the Sigmoid Colon more than the Ascending colon, although it's not known whether a longer term response effects more of the colon.

The reflex to these electrical signals is the same as those that cause the urge to have a bowel movement when pressure builds up in the rectum.