Cholesterol is a type of fat in our bodies. It helps us do a lot of things: build cells, digest food, and make hormones.
While cholesterol is needed for our body to function properly, too much of it can be bad. High cholesterol can cause serious problems in our blood, like clots, plus heart and brain issues.
Scientific theories are modified because they are out of date. Scientists are constantly discovering new things, and there are often amazing breakthroughs in science, so quite often, hypothesis are in need of an update.