This Makes Me Sick

It has been almost 2 years since I experienced my first episode of severe nausea during an ultra. I have dealt with it during every ultra since then. The worst was at Leadville in 2008 where I dropped at 60-miles. I walked nearly 70-miles of the 2009 Rocky Raccoon after my stomach betrayed me. I went back to Leadville in 2009 only to get sick at 40-miles and finish just 11-minutes before the final cutoff time.
These stomach issues have certainly put a damper in my love of ultrarunning. What gives me hope is that I ran my first three 100-milers with virtually no stomach issues (my first 100-miler is still my fastest). I have spent the past 2 years trying to understand what is causing this. What is different? Why can I run 70-miles per week in training with no stomach issues but start throwing up 40-miles into an ultra? Understanding this problem has proven to be much more difficult than I originally thought. There are so many variables involved that there is no single thing that will "fix" it. Plus, since I don't have problems during training, I only get to try out new theories during a competitive run.

My prevailing theory at the starting line of the 2010 Rocky Raccoon 100-mile run was that I had been over-running my training. When you run too hard for too long, your body diverts blood away from "non-essential" functions like digestion. The stomach shuts down and simply stops processing. Eventually the stomach gets too full and puts a return-to-sender label on everything in it. I had stepped up my training intensity considerably in preparation for this race, so I was hopeful that I would be able to get through it without stomach issues. I was wrong.
I started throwing up after the first 30-miles. This was exactly like what I had experienced a year previous, even though I was in better shape and started out at a slower pace. I quickly resigned myself to working through the nausea the last 70-miles in order to try and understand what was going on.
I discovered that even though I was puking all the time, my stomach was still processing stuff. This was encouraging since that meant I could keep moving without fear of severe dehydration. It wasn't very pleasant, but I worked out a system where I could drink fluid until my stomach rejected it and then fill it back up again. This would give me about 20-minutes of absorption until I would have to start the process over again.

I estimate that I puked more than 50 times before crossing the finish line with a time of 23-hours and 45-minutes.. It was ugly ... VERY ugly ... especially to those who were running near me, but I was thrilled to make it in under 24-hours despite having the severe nausea issues. Another encouraging fact was that, other than the nausea, I felt great. My pace was limited by my stomach rather than my legs, so if I can just figure out the nausea problem, I should see a huge improvement in my times.
I did quite a bit of research after returning home and I now believe that my issues have been due to a simple "acid stomach". In my first few ultras, I ate more solid food than I have been recently. It seems that solid food acts to buffer the digestive system to reduce the acidity being introduced into the stomach by most sport drinks. I also had changed my sport drink from what I used originally. I took some measurements and found that my new sport drink was significantly more acidic than my old one. Two seemingly minor variables that obviously have compounded to cause a big issue. Who would have thought that the margin for error in a 100-mile run was so small?
In just over a week I will be running a 24-hour ultra in Iowa where I am going to try out some solutions to the acid-stomach problem. First, I am planning to eat significantly more solid food during the first 50-miles of the run. As for my sport drink, I am planning to dilute everything 50% with water and add a pinch of baking soda to reduce the acidity. I have found that about 1/8-tsp of baking soda for every 24-oz of fluid results in a pH level that is just above neutral for most sport drinks. I will also be taking a bag of Rolaids to chew on as soon as the first signs of nausea begin to hit.
I have tried all of this in training, now I'll just have to wait and see if it works during a race. I really hope it does, especially since the race is on a 1/4-mile track. It will be a LONG day for everyone involved if I puke as much as I did at the Rocky Raccoon.

UPDATE:

Well, reducing the acidity of my drinks made absolutely no difference with my nausea during the race in Iowa.  I started throwing up at 50-miles and was sick the rest of the race.  I still managed to finish 1st place male with just over 111-miles but it wasn't pretty.  Back to the drawing board ...