Gastrointestinal upset when we excercise

There really is no debate- in order to perform at your best during endurance exercise, you need to fuel properly.  For events lasting 45 minutes or more, that means taking in some carbs throughout the event (usually 30-60g/hour).

While most people know this, in practice it's not always possible to take in enough sugar because of GI upset.  Do not fret- hope is not lost!  There are measures that can be taken to try to decrease the odds of experiencing stomach problems.

Causes:

First, it is important to understand that not all causes of GI upset are related to dietary issues.  Some common reasons athletes have issues that are NOT related to diet include: decreased blood flow to the organs (aka splanchnic hypoperfusion), a decreased ability of our intestines to move food through our system, and even pure mechanical damage to the intestines.  For instance, the jarring and pounding motion of running can directly cause damage to the epithelium that lines our intestines.  

Nutrition:

The above causes of GI upset are a little harder to manipulate, but nutrition is definitely something that can be changed and influenced to decrease the odds of GI upset.

There is no doubt that some athletes respond better than others to eating while exercising   That being said, researchers know that EVERYBODY has the ability to adapt and improve.  The key concept in reducing GI upset is this:

Reduce the amount of time whatever you are taking in stays in the intestines.  

The longer the food we ingest stays in our intestines, the more likely water will travel into our intestines.  As these guys discuss, if we can absorb our food quickly, the probability of GI upset goes down.  So how do we do that?

Rule #1: Avoid foods that do not absorb quickly.

Fats, proteins and fibres are important components to a complete and healthy diet.  But, there is just no reason to be ingesting them during competition.  They are difficult to absorb and digest (or in the case of fibre, not digestible at all).  This results in increased time spent in the intestines, which accelerates water loss, and predisposes us to GI problems.  More importantly, they provide no additional benefit to performance over simple carbs- it's just a more challenging way to fuel your activity.  So get rid of the gels, powerbars and everything else with protein and fat- it's not helping (I seriously hope there isn't a gel out there with fibre).

In addition to fats, protein and fibre, it is also crucial to avoid the wrong types carbohydrates.  While complex carbohydrates (i.e. the type of carbs found in our multi-grain bread, pastas etc) are good for daily use, they are harder to absorb.  Even fructose, the sugar found in fruit, is a different shape then glucose, and is more difficult to absorb.  While you race, this is the one time in your life where simple glucose is best.  There is some research pointing to the combination of fructose and glucose being an effective strategy, but when in doubt, stick to glucose.

Rule #2: Practice 

It seems like common sense, but not everybody does it.  If you plan on racing while ingesting carbohydrates, then you better practice.  Studies show that the more you train with carbohydrates, the more efficiently your body will adapt to utilizing them.  

For instance, this 2010 study looked at 16 cyclists and how they adapted to two nutritional regimes; a low carb and high carb protocol.  After getting used to their nutritional plan, the athletes were put through a 100 minute steady ride.  The researchers found that the high-carb fueled athletes showed an increase from 54.6g of glucose use during the earlier trials, to up to 63.6g by the end.  By contrast, the low-carb fueled group showed no increase in glucose use when comparing their initial and final 100 minute ride.  What this indicates is that with practice, your ability to utilize carbs during exercise improves, and thus the risk of GI upset should decrease along with it.

Rule #3: Stop taking NSAIDs

It's something that most athletes know- NSAIDs (non-steroidal anti-inflammatories) such as Ibuprofen, significantly increase the odds of GI upset and intestinal bleeding, as this study shows.

Heck, Ibuprofen can even cause more serious consequences, like it did for this UK gentleman.  The man died, in part because of the NSAIDs he was taking.

The death part is unlikely, but the GI upset is common.  The answer is simple: don't use NSAIDs, especially during your race.

Rule #4: Stay hydrated

This is an obvious one- but at the same time you don't want to consume too much.  How much are you supposed to drink?  I wrote about that HERE.

So what to do?

Some are lucky and don't suffer GI issues, while others constantly struggle with it.  That being said, we all can improve, and here's how:

• Avoid fats, proteins and fibres during
• Avoid complex carbs during
• Practice with your simple carbs DURING
• Stay away form NSAIDs
• Drink enough water

Follow these tips, and you will be thinking: "Gee, I think my GI issues have never felt better."