They say that that it's important to cook food thoroughly, particularly meat, to kill any harmful bacteria that may be present.
But when it comes to reheating food, you must make sure it is steaming hot all the way through, and don't reheat food more than once.
Here are eight foods you should take care to avoid reheating unless you want to book a day away from work - and in the bathroom instead.
It's a good one for soup, but when you are reheating it, take out celery.
The nitrate contents of the vegetable can be a problem if you heat it for the second time, as the heat can cause it to turn toxic.
Meals that contain eggs are generally fine to reheat as long as you make sure they're piping hot.
But beware boiled or scrambled - reheating those bad boys can make you sick.
Like celery, the nitrates which give it some goodness don't like being reheated and can have carcinogenic properties. if you've any left over, just ditch it.
Careful with this food staple.
If potatoes are left to cool at room temperature and then left unrefrigerated, conditions may be right for growth of botulism, and when you reheat and much, you're in big trouble.
Eat as soon as you prep with mushrooms - it's an easy rule that will save your stomach, because of the deterioration of the proteins in them.
Rich in nitrates, this purple veg is just waiting to give you a tummy ache, so better to eat it cold when it's been cooked and avoid all risk.
Reheating chicken is known as a tricky one.
The protein composition changes when a cold chicken is heated for the second time after being kept in the fridge which can cause digestive problems.
If you're attempting it, make sure the inside is piping hot.
Rice is a common leftover item, but you CAN get food poisoning after re-heating it. That said, the Food Standards Agency explains: "It's not actually the reheating that's the problem – it's the way the rice has been stored before reheating.
"Uncooked rice can contain spores of bacteria that can cause food poisoning. When the rice is cooked, the spores can survive.
"Then, if the rice is left standing at room temperature, the spores will multiply and may produce poisons that cause vomiting or diarrhoea. Reheating the rice won't get rid of these poisons."
Essentially, the longer you leave rice to stand in room temperature the more of a danger it poses to your and your health.