I'm no PRT champion, but to the 12th-hour diet-nazi's out there: ALL CRAP. I guarantee you that the SEAL and USMC candidates out there aren't pumping themselves full of oatmeal and aspirin so that they break the 12 minute barrier for 1.5 miles.
"The more you sweat in training, the less you bleed in battle." If you want a good PRT score, train for it and make it happen. The 3 or 4 seconds you gain from your new $150 aerodynamic shoes and protein pill diet aren't going to make the board accept you.
For significant improvement in results, you can't fake it. My advice: pretend your plane got shot down and you've got a platoon of pissed-off Iraqi soldiers chasing you around the track. Ask them about the daisy cutter they had for breakfast and whether it had enough fiber content.
Best eating advice I ever got from my old coach: "eat what your body is used to". If you're used to eating burgers and pizza, a trip to the salad bar is gonna clean you out better than Drain-o. Better bring a change of underwear.
<stepping off soapbox>