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What’s Healthiest: Steel-cut, Rolled, or Instant Oats?

Does it matter what kind of oatmeal you eat? Are steel-cut (or Irish) oats healthier or more nutritious than regular oats?

I think you will be surprised by the answer!

First, here is a breakdown of the different types of oatmeal:

Oat groats: All oatmeal start as groats, which are hulled, toasted oat grains. (Removing the hull doesn’t remove the bran, by the way.)

Steel-cut (Irish) oats: This is the least processed type of oatmeal. The toasted oat groats are chopped into chunks about the size of a sesame seed. Like those found in McCann’s Irish Oatmeal’s metal tins, steel-cut oats are almost entirely intact, including the bran. They’re high in fiber, burn off slowly, and will keep you feeling full for hours. But the downside is it takes around 30 minutes to make a pot of hot cereal in the morning.

Stone-ground (Scottish) oats: These are the same as steel-cut (Irish) oats, but they are ground into smaller pieces, closer to the size of a poppy seed, and only take about 20 minutes to cook because they are smaller.

Old-fashioned rolled oats: These are made by steaming the toasted groats and then running them between rollers to create flakes, making them slightly lower in fiber than steel-cut oats. But since they’re much more convenient, they take a fraction of the time to cook. They sit in a nice mid-position on the GI index, have nearly as much protein as steel-cut, and are ideal for making granola or muesli.

Quick-cooking oats are rolled into thinner flakes, so they cook a little faster.

Instant oats: These are the most heavily processed. The groats have been chopped fine, flattened, pre-cooked, and dehydrated. Instant oats are often found in packets and cups (think apples & cinnamon or maple and brown sugar). Unless you’re buying plain, they’re high on the glycemic index and often contain a lot of sugar.

So, Are Steel-Cut Oats The Healthiest?

You might assume that rolled oats would be less nutritious than steel-cut oats because they go through a little more processing, but the differences are minor. Steel-cut, stone-ground, old-fashioned, and quick-cooking rolled oats are all made from whole grains, and they all have about the same amount of fiber, protein, calories, and other nutrients.

In particular, oats are a good source of soluble fiber (which keeps you fuller longer). Soluble fiber can help reduce cholesterol and help keep blood sugar levels steadier—which helps manage and prevent diabetes and keep your appetite in check.

Do Steel-Cut Oats Have a Lower Glycemic Impact?

The glycemic impact is how fast food is digested and converted into blood sugar. Foods with a lower glycemic load are more slowly converted into blood sugar, and lower and slower are generally better.

Because steel-cut oats are chewier, denser, and somewhat less processed than rolled oats, you might expect that their glycemic load would be lower. Again, the differences are minor, and Steel-cut, stone-ground, and rolled oats are all in the same ballpark as far as glycemic load goes.

What About the Glycemic Impact of Instant or Quick-Cooking Oats?

The glycemic load of quick-cooking and instant oats is higher than that of rolled or steel-cut oats, which means that a bowl of quick-cooking or instant oats might not keep you full as long as rolled or steel-cut oats would. Nonetheless, as long as you stay away from the added sugar, quick-cooking and instant oatmeal are still considered low-glycemic carbohydrates.

What Is the Serving Size of Oats?

A serving of oats is 1/2 of a cup of rolled oats, 1/4 of steel-cut oats, or three-quarters of a cup cooked oatmeal.

What about Gluten-Free Oatmeal?

Oats themselves are naturally gluten-free. But cross-contamination can occur in facilities or fields where wheat, rye, or barley is present. There’s no need to buy gluten-free oatmeal if you don’t have a gluten intolerance.

Bottom Line

The most significant differences between steel-cut, stone-ground, and rolled oats are the texture and the cooking time. So, it comes down to which type you prefer—and how much time you have to cook them. If you like a hearty, chewy cereal, you might like steel-cut oats. But you’re not losing out on anything nutritionally by choosing old-fashioned rolled oats instead. And to be honest, that’s what I buy.

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