I was in Mumbai for a week and did not get stomache ills, but I was vigilant. No ice, no uncooked food, only bottle water, even when brushing my teeth. Kept mouth closed in the shower.

One of my colleagues who spent a great deal of time in India swore by using Pepto Bismol prophylactically, taking some before every meal.

If your bf is going to be touring, tell him to be cautious of buying bottle water from street vendors. Check the seal before walking away. It's not unheard of for them to re fill bottles.