On September 10th four of the Sal's Racing Team members will be competing in the Lake Placid Half-Ironman race. Two other members are their own relay team. None of us will be finishing in the 4-4:30 time range like the professional athletes, so nutrition almost becomes the fourth discipline.
Most races, whether official IM races or not, have a particular sponsor who supplies much of the nutrition sources on the course. (IM LP Suppliers Here) In longer races it's unlikely you can carry all of your own gels, fluid, etc, even if you have a preferred brand. Eventually, then, you succumb to using what the race organizers provide. This makes it vital that you try the race-day products throughout your training. At the very least figure out what, and how much, you should be consuming in transition 1 & 2 and while on the bike. With a bit of luck and good weather, this will make the run a bit easier and not a total bonk.
Jan and I began using Hammer Nutrition products years ago when she first began training for the full Ironman. They seemed to work well, weren't filled with simple sugars like many supposed endurance supplements, and didn't upset my stomach (or hers). Hammer has a guide; Hammer Nutrition's Secret of Success for Endurance Fueling Guide that is useful to read. Practicing all of this is vital though. I've gone into workouts and races feeling hungry and maybe only taking a gel or two and some water to begin and worried if I had done enough. Unless it's an ungodly hot, humid, high dew point day, it's amazing how little fuel you really need to begin a race. But maybe you can eat before a race. Fine, but figure out the best time to do so and what you really should be consuming.
All of this must be practiced. Try getting on the bike early in the morning and not eating solid food and just take a gel with water before leaving. Take gels, electrolyte fluids, maybe pretzels, Endurolytes, or other supplements during the ride and see how you feel. We did a 56 mile ride last week under cloudless, sunny skies and I thought my 60 ounces of fluids (Hammer Perpetuem, Endurolyte Fizz and water) would be enough. We also had Gatorade Energy chews. I had a really rough time over the last 10 miles and once home had 20 more ounces of water and a regular Coke before feeling better.
But now I know if race day is warm and sunny I'll need to rely on fluid from what's on the course in addition to what I carry on my bike. I'll also take a couple of minutes to hydrate in T1 and T2. Keeping this in mind today I ordered Gatorade Endurance Formula and HotShots (supposed to help prevent cramping) online. Using the link provided by the IM site you can get 50% a six-pack of HotShots.
Good luck and keep hydrated!