It’s a well-known fact that it’s almost impossible to cook the right amount of rice. It’s also pretty well-known that reheating those mountains of rice leftovers should be avoided, since it can give you food poisoning.
I’m pretty sure the boys I lived with at uni flouted that rule, but I’m also certain they’ve eaten so many technically non-consumable things that they’re now invincible. Good job, guys.
However, for us mere mortals, it’s necessary to take precautions.
It’s the post-cooking treatment of rice that makes it more likely to give us food poisoning: rice frequently contains spores which, left to their devices in a cosy, warm environment, grow into toxin-producing bacteria. That doesn’t mean you have to throw away your leftovers, though.
To reheat rice safely, when it’s first been cooked cool it as quickly as possible, ideally within an hour – for example, by running it under a cold tap. Keep it in the fridge for no more than a day, make sure it’s steaming hot the whole way through when you reheat it, and don’t reheat more than once.