I'm familiar with the idea of carb-loading but had a couple ideas that I haven't seen mentioned...
1) Iron-loading for extra hemoglobin to carry oxygen,
2) I read somewhere that it's not lactic-acid responsible for the burn & fatigue but H-ions and lower pH of the blood? If that's true then how about an alkaline meal prior to the race (or pop an antacid right before the start?)
What do you eat to improve your running times?
First let's get obvious out of the way. Not one micronutrient will help if there's not enough fuel for body to burn. Eat simple carbs for short runs or if you want to get energy quickly, but for longer runs body needs complex carbs.
Also drink enough. Drinking only water might not be enough - especially if you are sweating a lot, because electrolytes get out of normal limits. If you don't like sports drinks than you can make one simply by adding small amount of salt to lemonade. There are a lot of recipes around.
As for point 1., try to keep your iron levels normal, to much iron might get you to hospital, overdose can kill. I'd suggest, you do exercises for VO2max, so body will get more efficient at using oxygen.
And no 2.: just because you eat alkaline meal, does not mean your muscles/blood will get less acidic. This is like saying eating fat will store as fat.
And some viewing material on the matter: