Digestive transit times - TMI

[LittleGreyCat]

Sort of off topic, but I am having a colonoscopy on Wednesday. I don't have any evidence of problems, but because I have had my piles checked out and reported occasional very minor bleeding they automatically shove a camera up you.

The main requirement is to empty your digestive tract completely so the camera can see where it is going.

Now the instructions say to have a light breakfast, not to eat after mid-day on the day before the procedure and start the flushing out process at 14:00.

Being nosey I looked to see how long it takes for food to be digested. Turns out it takes 6-8 hours to get through the small intestine and 2 days to be properly digested in the large intestine. So I see no real point (apart from staving off hunger pangs) to eat at all when I am about to eject it soon after with no major benefit. Mean, I know. Blame rationing.

On the diabetes front it does make me wonder about the focus on getting your BG back down within 2 hours if most of the meal is going to be hanging around being digested for a couple of days. If you have a load of meat (mainly fibre, protein and fat) hang in around for between 2 days and 2 weeks (depending on what you read) then how does that affect your BG?

Anyway, assuming that I am still fat adapted a little bit of fasting shouldn't do me much harm. Must remember to politely refuse the sugar in the tea and the biscuit afterwards. Although that is mental discipline. One rich tea after a day of fasting isn't going to send me dangerously hyper.

 

[ringi]

On the diabetes front it does make me wonder about the focus on getting your BG back down within 2 hours if most of the meal is going to be hanging around being digested for a couple of days.

The carbs are absorbed within a short time of eating them.

 

[DCUKMod]

I'd agree with @ringi . For the sugars, digestions starts in the mouth, whereas starches take a little bit longer, and so on. Please don't ask me to go back to that level of metabolic physiology!

From what I understand of the process, it wouldn't be a good idea to have plans involving travel of more than 5mtrs from the smallest rooms tomorrow.

Good luck on Wednesday.

 

[LittleGreyCat]

I'd agree with @ringi . For the sugars, digestions starts in the mouth, whereas starches take a little bit longer, and so on. Please don't ask me to go back to that level of metabolic physiology!

From what I understand of the process, it wouldn't be a good idea to have plans involving travel of more than 5mtrs from the smallest rooms tomorrow.

Good luck on Wednesday.

Been there and done that a few years back for a Sigmoidoscopy which only looks up as far as the first bend. Just as well we have two toilets. Possibly TMI again.

I was mainly pondering on the effects of the slower to digest fats and protein on BG levels. Sources disagree but it seems that it takes about 6-8 hours for food to pass through the stomach and small intestine where a lot of nutrients are absorbed. I assume that these are the ones which show up most in blood tests because you are supposed to fast for 12 hours for a fasting test. There doesn't seem to be much about how long it takes to absorb the rest of the food, and at what rate this happens. If it takes up to 72 hours (minimum 33 hours I think) for food to pass through then it is spending 24 to 60 hours in the large intestine.

If you are on a water fast then you are apparently still getting some nutrition 2-4 days later from the gut contents. I wonder how long it takes, for example, to extract 75% of nutrients from the gut.

 

[Brunneria]

I think it is mostly water that is absorbed in the colon, with the nutrients having been absorbed further up in the small intestine. So I'm not sure you are getting much energy/nutrition once it gets past the appendix. So all the blood glucose raising stuff will have happened between the stomach and the appendix.

At least, that is what I understood from my biology lessons at school.

I'm also not sure about the overall length of time (gut transit time). It is highly variable. I remember talking to a Hindu monk once. And he was explaining that on a diet of fruit and veg with very little dairy, he would expect gut transit to be about 8 hours. With movements 3x a day, one for each meal. Anything else and he would think it was constipation.

Compare that with the average Westerner, on a low veg, high processed carb diet, and we are led to believe that gut transit is 'normal' so long as we go every day or two, with no idea how long it was actually in there...

I think the ideal is probably somewhere between those two scenarios, but how do we each know what is right for us and our personalised ways of eating?

Sorry, that was a bit of a ramble.
Good luck with your procedure.
And the preliminaries!

 

[Alexandra100]

On the diabetes front it does make me wonder about the focus on getting your BG back down within 2 hours if most of the meal is going to be hanging around being digested for a couple of days. If you have a load of meat (mainly fibre, protein and fat) hang in around for between 2 days and 2 weeks (depending on what you read) then how does that affect your BG?

This extract from Dr Bernstein's "Diabetes Solution" goes a little way towards answering your query. He states that it is not the digestion of food that raises bg, but the initial reaction of our saliva to it at first bite:
"Let’s take another look at that mixed breakfast and see how it affects a type 2 diabetic. Jim has the same toast and jelly and juice and boiled egg that Jane, our nondiabetic, and I had. Jim’s blood sugar levels at waking may be normal.* Since he has a bigger appetite than either Jane or I, he has two glasses of juice, four pieces of toast, and two eggs. As soon as the toast and juice hit his mouth, his blood sugar begins to rise. Unlike mine, Jim’s pancreas eventually releases insulin, but he has very little or no stored insulin (his pancreas works hard just to keep up his basal insulin level), so he has impaired phase I secretion. His phase II insulin response, however, may be partially intact. So very slowly, his pancreas will struggle to produce enough insulin to bring his blood sugar down toward the normal range. Eventually it may get there, but not until hours after his meal, and hours after his body has been exposed to high blood sugars."

 

[LittleGreyCat]

I think it is mostly water that is absorbed in the colon, with the nutrients having been absorbed further up in the small intestine. So I'm not sure you are getting much energy/nutrition once it gets past the appendix. So all the blood glucose raising stuff will have happened between the stomach and the appendix.

At least, that is what I understood from my biology lessons at school.

I'm also not sure about the overall length of time (gut transit time). It is highly variable. I remember talking to a Hindu monk once. And he was explaining that on a diet of fruit and veg with very little dairy, he would expect gut transit to be about 8 hours. With movements 3x a day, one for each meal. Anything else and he would think it was constipation.

Compare that with the average Westerner, on a low veg, high processed carb diet, and we are led to believe that gut transit is 'normal' so long as we go every day or two, with no idea how long it was actually in there...

I think the ideal is probably somewhere between those two scenarios, but how do we each know what is right for us and our personalised ways of eating?

Sorry, that was a bit of a ramble.
Good luck with your procedure.
And the preliminaries!

I can fairly accurately report the transit time of a Waitrose curry, having previously seen video evidence that my large intestine was absolutely empty.

I ate around 17:00 Wednesday and there was significant transit by 09:00 Thursday morning.

So that make it 14 hours by my reckoning, also noting that I am assuming that it could have been potentially faster but that I was asleep for a lot of the time.

Nothing major found but some tiny polyps removed. Looked this up and apparently 25% of the population have these at some point so no immediate worries. Fascinating experience with some seriously impressive technology and a good team looking after me.

The flushing out experience was "interesting" in that (apart from the "will it never stop?" moments) the liquid was very hard to drink. 3 sachets each mixed up with 1 litre of water is a lot to drink if it is mildly unpleasant in taste. However it worked.

Note on the fasting front - I don't seem to have lost any weight.

 

[Mr_Pot]

He states that it is not the digestion of food that raises bg, but the initial reaction of our saliva to it at first bite:

I find that very hard to believe. I could understand Insulin being released when first tasting food, anticipating the expected increase in blood glucose. An immediate increase in blood glucose on first tasting food would mean the body was releasing glucose into the blood stream to prepare for more glucose which seems illogical..

 

[Brunneria]

I find that very hard to believe. I could understand Insulin being released when first tasting food, anticipating the expected increase in blood glucose. An immediate increase in blood glucose on first tasting food would mean the body was releasing glucose into the blood stream to prepare for more glucose which seems illogical..

It is called the Chinese Restaurant Effect, and has been fairly widely discussed.

https://www.facebook.com/ZeroCarbZen/posts/1263044737047961 (this is an extract from Bernstein's own text)

https://www.diabetesselfmanagement.com/blog/foods-strange-tricks/

https://www.diabetesdaily.com/forum/articles-by-members/33081-effect-zero-carb-foods-blood-sugar/

 

[LittleGreyCat]

I find that very hard to believe. I could understand Insulin being released when first tasting food, anticipating the expected increase in blood glucose. An immediate increase in blood glucose on first tasting food would mean the body was releasing glucose into the blood stream to prepare for more glucose which seems illogical..

Interesting to test, as well.

Presumably if you just touched a small piece of bread to your tongue then you would get the saliva response without consuming any carbohydrates. Then you could check if your BG went up (liver dump, but why?) or if your BG went down (insulin response in anticipation of food) or if nothing happened (body not so easily fooled).

 

[LittleGreyCat]

It is called the Chinese Restaurant Effect, and has been fairly widely discussed.

https://www.diabetesselfmanagement.com/blog/foods-strange-tricks/

https://www.diabetesdaily.com/forum/articles-by-members/33081-effect-zero-carb-foods-blood-sugar/

Interesting.

I read "So eating large amounts of anything, “even sawdust” says Bernstein, could raise your blood glucose."

The Chinese Restaurant effect seems to be tied to food stretching the gut, not to a saliva response. The example was a whole head of lettuce with minimal carbs causing a large rise in BG.

This does make me wonder if this happens in those who are mainly fat burning; the liver dump/dawn phenomenon seems more controlled with LCHF so I'm not sure how much the liver stores/dumps.

Wandering back to digestive transit times, I also read (about the Pizza effect)

"Other meals that combine lots of carbohydrate with fats and/or proteins could have the same effect. Jan Chait posted here five years ago about a big spaghetti fest she had with her husband. The pasta was covered with a fatty sauce, with a side of garlic bread and lots of butter. Because of the fats (the pizza effect,) her blood glucose levels were up for two days, instead of just spiking high for an hour or two.".

This implies that the food was still active two days later, and still raining BG. Confusing when up thread we have discussed it being all over bar the shouting in 6-8 hours. Perhaps you have to clench your buttocks really tightly for this effect to work?

Or perhaps there was something else going on; hard to visualise someone having a spaghetti fest then not eating anything else for 2 days.

 

[Alexandra100]

I find that very hard to believe

Here is an extract from "Diabetes Solution".
"Let’s take another look at that mixed breakfast and see how it affects a type 2 diabetic. Jim has the same toast and jelly and juice and boiled egg that Jane, our nondiabetic, and I had. Jim’s blood sugar levels at waking may be normal.* Since he has a bigger appetite than either Jane or I, he has two glasses of juice, four pieces of toast, and two eggs. As soon as the toast and juice hit his mouth, his blood sugar begins to rise. Unlike mine, Jim’s pancreas eventually releases insulin, but he has very little or no stored insulin (his pancreas works hard just to keep up his basal insulin level), so he has impaired phase I secretion. His phase II insulin response, however, may be partially intact. So very slowly, his pancreas will struggle to produce enough insulin to bring his blood sugar down toward the normal range. Eventually it may get there, but not until hours after his meal, and hours after his body has been exposed to high blood sugars. Insulin is not only the major fat-building hormone, it also serves to stimulate the centers in the brain responsible for feeding behavior. Thus, in all likelihood, Jim will grow even more overweight, as demonstrated by the cycle illustrated in Figure 1-1.

Since he’s resistant to insulin, his pancreas has to work that much harder to produce insulin to enable him to utilize the carbohydrate he consumes. Because of insulin’s fat-building properties, his body stores away some of his blood sugar as fat and glycogen; but his blood sugar continues to rise, since his cells are unable to utilize all of the glucose derived from his meal. Jim, therefore, still feels hungry. As he eats more, his beta cells work harder to produce more insulin. The excess insulin and the “hungry” cells in his brain prompt him to want yet more food. He has just one more piece of toast with a little more jelly on it, hoping that it will be enough to get him through until lunch. Meanwhile, his blood sugar goes even higher, his beta cells work harder, and perhaps a few of them burn out.† Even after all this food, he still may feel many of the symptoms of hunger. His blood sugar, however, will probably not go as high as mine would if I took no insulin. In addition, his phase II insulin response could even bring his blood sugar down to normal after many hours without more food."

You can read the whole chapter online at http://www.diabetes-book.com/nondiabetic-versus-diabetic/

 

[Mr_Pot]

I read "So eating large amounts of anything, “even sawdust” says Bernstein, could raise your blood glucose."

The Chinese Restaurant effect seems to be tied to food stretching the gut, not to a saliva response. The example was a whole head of lettuce with minimal carbs causing a large rise in BG.

I agree, you saved me typing that. So I still find it hard to believe that glucose levels in the bloodstream increase when you still have the food in you mouth.