Unstabilised, rolled, steel cut: The difference between types of oats explained

Steel cut, rolled, unstabilised, quick, protein, overnight … what’s the difference between all the oats in your supermarket aisle and which one is best?

If you’ve walked through your local Woolies or Coles to pick up some oats for breakfast it can be hard not to feel confused and overwhelmed.

Boxes and packets of different varieties fill the aisle.

Rolled, unstabilised, protein, quick, steel cut.

There are a lot of choices – and that’s before you even think about granola or muesli.

But what’s the difference between them all? And what’s best for you?

We asked Associate Professor Sara Grafenauer, the program lead for nutrition, dietetics and food innovation at the University of NSW, to break it all down.

She’s a dietitian and a member of the advisory board for Oats Australia, which is part of Grains Australia.

Assoc Prof Grafenauer said the position was unpaid and she didn’t have any financial deals or interests with oat companies.

She said she was just passionate about oats.

“It’s really because of my interest in whole grains, that’s why I am part of it,” she said.

She said oats were a great source of beta-glucan, a type of soluble fibre that could help people control their cholesterol levels and remove unnecessary fats from the blood stream.

“We’ve actually done a nutrition-economics study where we’ve shown three serves of whole grain foods, like oats, could save Australians or the government $1.4bn annually just in related healthcare costs for type-two diabetes and cardiovascular disease,” she said.

“So that could be your porridge at breakfast, it could be a couple of slices of wholemeal bread at your lunch or using one of the amazing wholegrain pastas that is now available.”

Assoc Prof Grafenauer said oats grew really well in Australia so were also great for farmers.

“They are actually a very sustainable food, the way their roots grow in the soil make them an excellent choice for Australian conditions,” she said.

“Oats play a big role in weed control, they are actually a natural herbicide because of their root network.”

Assoc Prof Grafenauer said research had found 68 per cent of the breakfast cereal aisle was made up from oat products.

That’s a lot.

So with all that in mind, which kind should you choose on your next supermarket visit?

ROLLED OATS

These are a 10/10 in choice, according to Assoc Prof Grafenauer.

“Through processing they are rolled and steamed which stops them from going rancid,” she said.

Rolled oats are a good choice and have beta-glucan.

She said that meant the good fats in the whole grain were protected.

A person’s body was also able to better access the all-important beta-glucan when they were rolled, she added.

Assoc Prof Grafenauer described this soluble fibre as nature’s Ozempic.

“We have quite a big problem with heart health in Australia,” she said.

“I have a private practice and I see people in their 40s with quite high cholesterol levels, so adding in some oats can be helpful.

Simple rolled oats can be a cheap option.

“The beta-glucan forms a gel in your bowel which slows things down and collects those cholesterol deposits, it actually produces that same GLP-1 like Ozempic.”

A study published last year in the Journal of Nutrition which tested mice found that beta-glucan helped them produce a short-chain fatty acid in their gut that stimulated the release of GLP-1, however it was far less potent than Ozempic.

QUICK OATS

This type of oats is steamed for longer and rolled thinner into smaller flakes so they cook faster in the morning for your breakfast.

Assoc Prof Grafenauer said this would give you a quicker rise in your blood-sugar levels and you wouldn’t feel as full for as long.

Quick sachets won’t keep you as full for as long.

“They are quite high GI,” she said.

“When you see instant oats on the market, they are flaked up and they will give you a quicker rise in your blood-glucose levels.

“It may not be as satiating, it may not keep you as full for as long.

“It may break down quicker in your system.”

She said she would not recommend them for people with diabetes.

“I don’t know why you need quick oats, my porridge takes just two minutes to make and if you don’t have two minutes to make breakfast you’ve got rethink your lifestyle,” she said.

STEEL CUT OATS

These are not necessarily the healthiest kind despite being less processed and lower-GI, according to Assoc Prof Grafenauer.

The difference is the whole groats are sliced rather than flattened, so they take much longer to cook and they have a nuttier taste.

“With steel cut it means the body can’t actually access the beta-glucan as much which is the helpful ingredient,” she said.

“It’s not accessible enough by the body … the body can’t get into that grain and access enough of the beta-glucan.”

OVERNIGHT OATS

Assoc Prof Grafenauer said packs labelled “overnight oats” were unnecessary and it was better to just buy rolled oats.

This was because it was easy to just make your own overnight oats by mixing them with milk, berries and yoghurt the night before.

It’s not that hard to make overnight oats yourself. And cheaper, based on these prices.

“Often overnight oats are going to have some sugar and other flavourings added,” she said.

“I think for Australian families, just working with the normal rolled oats is much more economical.

“Add milk and yoghurt and leave it in your fridge overnight.”

FIVE GRAINS PORRIDGE

This has more grain variety in it – but that’s not necessary for a balanced diet, according to Assoc Prof Grafenauer.

There's a lot to choose from when it comes to oat products.

She said Aussies tended to get enough wheat from other foods.

“We’re very good in Australia in getting wheat, we tend to have wheat bread and pasta, so having oats is a way of getting a different grain … I don’t think you need to get the five grains variety.

“It is a way of getting a variety of grains, but whether they all cook evenly is another thing, you might have some which are a bit harder to chew.”

UNSTABILISED ROLLED OATS

These oats have not been steamed meaning the lipase – an enzyme – remains active.

Advocates say they may potentially be more nutritious, but the downside is they will go rancid a lot quicker.

Unstabilised rolled oats are not steamed and will go rancid faster.

“They would still give you the beta-glucan but the issue here is when the fragile oil in oats go rancid they are no longer good for you,” Assoc Prof Grafenauer said.

“When they are rancid they won’t have the same health benefits.”

When asked if unstabilised oats were better than the stabilised version while fresh, she said: “I don’t there’d be any evidence they’d be substantially better”.

She said you would be able to smell if the unstabilised oats went rancid.

PROTEIN OATS

These are much more expensive oats – costing $8 – that contain soy protein crisps and soy isolate.

“It’s messing with your oats, I don’t think there’s any particular value in doing that,” Assoc Prof Grafenauer said.

GRANOLAS

Crunchy clusters of oats with nuts and seeds, these are good if you cook them at home in your oven.

But Assoc Prof Grafenauer said supermarket pre-packaged granolas weren’t as good as just plain oats otherwise.

“They tend to be higher in fat and have added sweeteners,” she said.

“To make those clusters like a biscuit you have to have something to glue it together and they use sugar and fat to do that.

“But if you made a homemade granola where you’re using seeds and grains and it’s just toasted in your oven you’d be fine.”

MUESLI

This is just rolled oats with seeds, dried fruits and coconut flakes.

“Really its rolled oats with the fruit mix and nut mix put in there,” Assoc Prof Grafenauer said.

“They can still add vegetable oil to keep things loose and separated.”

She said she often got people to sprinkle muesli or granola on their porridge for some texture.

Originally published as Unstabilised, rolled, steel cut: The difference between types of oats explained