Which of the following foods is most likely to lower blood cholesterol levels?

Oatmeal is recognized for its potential to lower blood cholesterol levels due to its high content of soluble fiber, particularly a type called beta-glucan. This soluble fiber works by binding to cholesterol in the digestive system and preventing its absorption into the bloodstream. Studies have shown that regular consumption of oatmeal can lead to significant reductions in total cholesterol and low-density lipoprotein (LDL), often referred to as "bad" cholesterol.

The other choices, while they have their own nutritional profiles, do not possess the same cholesterol-lowering effects. Butter and cheese are both high in saturated fats, which can contribute to increased blood cholesterol levels when consumed in excess. Combined oils may vary in their types of fats but generally do not specifically target cholesterol levels the way soluble fiber does. Therefore, oatmeal stands out as the most effective option for promoting heart health by lowering blood cholesterol.