Food In India

The main thing people said to me when I told them I was going to India was "Take some Imodium" or "You'll get Food poisoning" and it seemed that any one from the west who has been to India Has returned with a story of some sort of illness. But what i cant work out is why it only seems to effect people from the west I mean there are millions of people that actually live in India and don't get sick.(with the exception of suresh and his dodgy stomach) so what is the difference.
heres the choices

1. Strong Constitution They have a stronger constitution and in the west we cant take all the strong flavored foods of the east. Maybe But I doubt it
2. Change In diet it may just be a matter of getting used to different diet
3. Eating with Hands. In the west we go used to using utensils to eat with but in India they have a much more hands on approach, even down to only using the right hand to eat and left to use everything else but as a westerner eating Indian food we use both hands and therefore would transfer more germs.
4. liars People who have traveled to India are exaggerating, Lying or are simply Unlucky.
5. Indians Do get sick but don't moan about it like us Brits.


I am open to any other theories but I kinda like number 3 myself, as I have found the food over here to be of the highest quality.