NEVER, EVER underestimate the power of the Delhi belly. For those who wonder, this is the clash between Intestinal Police and Delhi Food Mafia. I've been caught repeatedly in that clash several times here in Delhi. The results are always horridly revolting and tremendously debilitating.
Seriously, Delhi belly—colloquialism for traveller's diarrhea—is not specific to Delhi. It's the most common illness afflicting travelers to India, mostly due to bacteria. In all my years traveling around the country, the illness has hit me worst and most often in Delhi, even if I have completely avoided the city's street food. The higher levels of spice and pollution are obvious culprits.
I've begun to stack up on Yakult, a proven probiotic, to fortify my intestinal immunity. In the meantime, let me enjoy the city's otherwise ambrosial and truly cosmoplitan culinary offerings. I have the Delhi. You can have the belly.