For example, cereal can be bad for diabetics. Most cereals contain a lot of sugar, which can cause the blood sugar levels of diabetics to rise dangerously high. Diabetics who like cereal should try to eat sugarfree cereal. They still have to be very careful because cereal contains a lot of starch, which changes to sugar after it is digested. Cereal is made from different kinds of grains.
Some people are allergic to certain grains, such as wheat.
These people must stay away from cereals that contain wheat. Also, cereal can be a choking hazard for very young children and toddlers. Even though I haven't actually witnessed a child choking on cereal, I am sure that it has happened. Bigger pieces of cereal might get stuck in the throat. Mushy cereal or cereal that mushes quickly is probably safer for very young kids, even if it may not taste as good.