Carbs and diarrhea?

Hi all,

I’ve noticed that on days with hard workouts (threshold or above) I suffer from diarrhea a few hours following the workout. I have a feeling this might be related to how many carbs I take in before and during the workout, but wanted to see if anyone else experiences something similar.

I’m a 98kg male and this is usually what I take in:

  • 1 hour before workout: bowl of oatmeal / 32g carbs
  • Start of workout: 3 clif bloks / 24g carbs
  • 20 minutes in (after warmup): 3 clif bloks / 24g carbs
  • Every 10 minutes: 1 clif bloks / 8g carbs
  • 1.5 scoop of Skratch hydration during the ride: 30g carbs

Depending on the length of my workout I generally take in 32g carbs before the workout and 126g-158g carbs during the workout; so about 158g to 190g total. This puts me under 2g/kg carb intake which seems safe to me, but I’m wondering if this is high on a relative scale. Please let me know and thank you!

I have crohns disease which doesnt necessarily help in giving you feedback but I do have trouble taking excess sugar as it leads to diarrhea. Now If I watch my diet pre workout it also plays a roll. I am fine with say Oatmeal for breakfast. I am better eating light before a workout and leaving at least an hour between food and the ride.

Sugar by itself outside of riding can be a trigger for me. Sugar when taken as part of my riding doesnt often cause problems but I have adjusted my pattern to determine what works best for me.

I do not use bloks as you do. I tend to save those for later in a ride which is generally a harder ride where I look for something extra. I work best with using GU’s roctane for my rides which I also alternate with a bottle with a Nuun tablet for hydration. If it is a ride of 2-3 hours I will also have a cliff bar as I find something more like food just helps the system.

If I translate it in the fashion you have I do not consume in the same fashion as you. Most of my rides would be 60 to 100g an hour. So you definitely consume more then I do.

I can only say to experiment and to try less to see if that works.

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That’s a lot of sugar/carbs per hour, at least to me. I’d probably get stomach issues, too. How long of a workout are we talking here, and what intensity?

For me (78-80kg), anything under 1.5 hours is typically just water, though I might throw in a scoop or two (15g per scoop) for a 700ml bottle if it’s a harder workout. When I did Polar Bear +1 last Sunday, I threw in 4.5 scoops. If it’s been a while since I’ve eaten before the workout, I might have something like a couple cookies or something like that, nothing big (breakfast is always oatmeal). If it’s not close to lunch or dinner time afterwards, and it was a harder workout, I’ll have a clif bar, banana, or PB&J sandwich or something similar. On a longer 3-5 hour ride outside, I do about 60g/hour in fluids, and a clif bar every 1.5 hours. That’s at the top end of what I’ll take in, if it’s an easy Z2 ride, it can be a bit less. Everyone’s different of course, but it’s definitely less than you’re taking in, even accounting for our weight difference.

I’ll throw this out there - have you tried something other than Skratch and/or the Clif Bloks? I use Sponser myself, no stomach issues. This fall I did try a canister of Dextro Energy Iso powder, and lordy lordy lordy, I don’t know which ingredient wasn’t compatible with me, but I was very close to making an appointment at the doctor (which takes a lot for me) because of, well, let’s just say the drastic change in digestion results, the whole nine yards, gas, bloating, smell, consistency, everything. I could make the dog get up and leave the room (it was like a super power, just a really crappy one). Then it dawned on me that it started when I switched to the Dextro, and it all went away when I stopped using it. Just a thought.

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I didn’t backwards calculate how long your working out for? But if that is for an 1hr-1.5hr it seems high. I think luckily it is an easy one to workout with a bit of trial and error. Backing it right off and seeing if it makes a difference. Then you can find your limit.

I can generally tolerate a decent amount of carbs/hour. But the minute there is a particular sweetener/additive i bloat quickly. So I know certain brands to steer clear of.

Below is a TR article:

There are different types of carbs. I have similar symptoms when using commercial sport drinks and energy bars, because they contain a lot of fructose (typically 2:1 ratio). My digestion system cannot handle fructose very well, so I try to avoid large amounts of it. I make my own sports drinks, based on maltodextrine. That works much better for me and is very cheap.

126g is a lot for a one hour workout but plenty safe for two hours so that isn’t super clear. My first thought is how much water are you taking in? Lots of carbs without enough fluid is a perfect recipe for gut rot, gas, bloating and diarrhea.

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Seems like alot of carbs…one way to find out would be to try a workout and only eat what you would eat on a recovery day, your body should have enough stored glycogen to get you through. Another thing to consider is you might have gluten tolerance issues?

Most of the recent info I’ve heard re: carb processing rates (from TR podcast and others) is around 60g/hr with glucose (? i think) and around 100g/hr with glucose and fructose [corrected per @mwglow15] to take advantage of multiple pathways (? i think). If you’re consuming way more than your body can process, that could explain your digestive issues.

Maybe cut back to 60g/hr and slowly increase until issues appear then dial it back to an amount your body can handle?

I think it takes a lot of trial and error to see what you can handle and increase amounts slowly. though your oatmeal 1 hour before goes against recommendations I’ve heard? my understanding is either 2-3 hours before or within 15 minutes of starting. Also try some higher GI foods instead of oatmeal?

Recently I’ve been trying to actively ‘fuel the work’ and train early morning. For a typical 90min workout I have 80g before (white toast w/jam & honey) then 120g in bottles. Will often have a recovery drink after for harder workouts. then oatmeal breakfast after that. A 90 min workout for me is often 1200-1500kJ and aim to be at least calorie neutral after breakfast. this has been working well without any gi distress.

I’ve been doing some longer (3-4hr) Z2 rides where I’ve been mixing in more solid food, this hasn’t been working so well (gi distress) and needs more experimentation!

That would be 100g/hr with a mix of glucose and fructose. Maltodextrin is essentially just a long chain of glucose molecules.

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If like me you eat a lot of porridge oats, you can get, ahem, a little more regular because of the fibre. Just a thought! I like to smash a big bowl on the morning of a workout, and often afterwards - 100g worth each time.

One strategy might be to just eliminate some variables and see if it makes a difference.
You could:

  • Try reducing the amount of carbs
  • Change the type of carbs
    ** Try something other than blocks. Maybe the gelatin or the type of sugar they use is messing you up.
  • Maybe try something with a bit less fiber close to the ride

Also is there something you are doing after your rides that might be causing it? Like a whey protein shake or something?

How do folks get the idea that you need all this sugar for a workout? The Bloks seem like the obvious suspect. Eat a banana with your oatmeal and you are probably good to go. The glycogen in your muscles is also filled up from dinner the night before. Save some bloks for races or exceptionally long rides but also take some real food along.