It is different from kind of foods= It depends on what kinds of food, but I think usually most foods are safe. I haven't heard any person died because of food in supermarket. However, sometimes some issues are released regarding foods in supermarkets.
For example, some bugs are found out in a bag of snack. Eating bugs are not harmful to our health, but disgusting.= Bugs are not really harmful to our health though it's disgusting. The severe problem is rotten food,=One serious problem is when foods are rotten or expired. but also it just makes us have a food poisoning. In short, there is a problem in food of supermarket, but that problem also appears in restaurant or other place. Moreover it is not huge problem. So food in supermarkets are safe.