There are many choices for oat products on the market. You can buy oatmeal, steel-cut oats, groats, oat flour, instant oatmeal, oatmeal bread and many more products. Two of the most popular oat products are oat bran and steel-cut oats. These may have the word "oat" in common but they are very different foods with just a few similarities.
Oat bran is the outer layer of the oat grain that is just underneath the outer hull. It is high in phenols and soluble fibre, which helps lower LDL, the bad form of cholesterol. Oat bran is usually sold in a jar or in bulk bins and can be easily sprinkled on foods in order to gain these heart-healthy benefits. Studies by Tufts University have shown that oat bran helps to stabilise blood sugar, making it a good choice for diabetics or those at risk for diabetes.
Steel-cut oats are simply whole oats that have been cut. That is usually the only processing they get, which leaves them high in soluble fibre. They are much higher in soluble fibre than instant oats, which have been cut and steamed, and often have additives like sugars and dried fruits added to them. Steel-cut oats are thick, so they take a long time to cook --- up to 30 minutes.
Steel-cut oats, like any oats, have oat bran in them. Oat bran, however, has no oatmeal as it has been completely separated from the oats it came from. Both are good at stabilising blood sugar and helping to reduce cholesterol, which in turn helps reduce the risk of heart attack and stroke. Though they do have these similar health benefits in common, that is where the similarities end as they are both very different foods, even if one is essentially derived from the other.
Steel-cut oats are whole oats that have been cut while oat bran is simply the substance underneath the hull. Steel-cut oats must be cooked before they are eaten, whereas oat bran is generally eaten raw, though not by itself. Oat bran is generally added to something like a smoothie or yoghurt or sprinkled onto salads and other foods. Steel-cut oats can be added to foods, but it can also be eaten by itself without anything added.