Sounds like you’re taking steps to ensure your diet contains heart-healthy whole grains and that’s terrific! Which ones are best can be a bit confusing and unfortunately when it comes to oatmeal, the information can be somewhat grainy. So let’s clear it up a bit by starting with some anatomy. Oats are similar in basic structure to other grains. Under the hull that’s milled away is a bran layer (helpful in lowering LDL or bad cholesterol). Beneath the bran layer is the endosperm-where most of the starch comes from. And finally the smaller remaining section of the grain is known as the germ-an area very high in nutrients. Old-fashioned oats are sometimes called rolled oats. They are the form most recognized throughout the U.S., England and Scandinavia. Quick-cooking oats are a thinner version of their old-fashioned cousins that soften faster in liquid. Steel-cut oats are simply the inner portion of the oat kernel cut into finer pieces.
The good news is that whether you choose old-fashioned, quick cooking, or steel cut, you are getting in your whole grains with similar nutrient profiles. The biggest difference between the 3 types of oats has to do with glycemic load. The glycemic load or impact is the rate at which a food is broken down to sugar in the body. The lower the glycemic load, the slower your body can convert it to sugar which translates to steadier blood sugar levels.
Old-fashioned and steel cut oats are very similar on the glycemic index, but quick-cooking or instant oats are much different. These thinner versions are meant to break down quicker when exposed to liquid, and basically hold those same properties during digestion. Our body rapidly breakdowns quick cooking or instant oatmeal which can lead to blood sugar spikes; not only a concern for diabetics but for the general population as well who want to feel full and satisfied throughout the day.
General Mills Corporation: What is Whole Grain Anyway?, accessed 2/25/2013, http://wholegrainnation.eatbetteramerica.com/facts/