Are Oats Good or Bad for Your Blood Sugar? What the Research Actually Says

Are Oats Good or Bad for Your Blood Sugar? What the Research Actually Says

By Diane Lietz, MSN, APRN, FNP-C | VGM Health | 5 min read

I'll be honest with you: for a long time, I was on the fence about oats. They're a starchy carb, and I'd heard over and over that oatmeal spikes your blood sugar. So when patients asked me, I hesitated.

Then I looked at the research more closely, and what I found changed my answer. The short version: oats can be a blood-sugar-friendly food, but which oats you choose, and how you eat them, make a big difference.

Not all oats are created equal

The more an oat is processed, the faster your body can turn it into sugar. A review of glycemic index (GI) studies on oats found that:

• Steel-cut oats had a GI of about 55.
• Old-fashioned (large-flake/rolled) oats had a GI of about 53.
• Quick-cooking oats jumped to about 71.
• Instant oatmeal came in around 75.

Steel-cut and old-fashioned oats land in the low-to-medium range. Quick and instant oats produced a significantly higher blood sugar response, because the smaller, more processed flakes are digested faster (Tosh & Chu, 2015).

That's likely where oats got their bad reputation. Many of us grew up on flavored instant packets, which are the most processed oats plus added sugar.

The fiber in oats works in your favor

Oats contain a special soluble fiber called beta-glucan. When it mixes with water in your gut, it forms a thick gel that slows down how quickly sugar enters your bloodstream.

A large analysis of 103 trial comparisons found that adding oat beta-glucan to a meal containing carbohydrates lowered the post-meal rise in blood sugar by about 23%, and lowered insulin by about 22%. This held true for people with and without diabetes, and the researchers rated the evidence as high certainty. The benefit depended on getting enough beta-glucan, and on the beta-glucan staying intact rather than being broken down by heavy processing (Zurbau et al., 2021).

The longer-term picture looks encouraging too. In studies lasting several weeks or more, eating whole oats or oat bran was linked to lower fasting blood sugar and lower HbA1c (your three-month blood sugar average), especially in people with type 2 diabetes (He et al., 2016; Shen et al., 2016).

Pairing matters: add protein and healthy fat

I didn't find a study that tested oatmeal plus protein specifically. But the broader research on how we eat carbohydrates is clear and consistent:

• When people with prediabetes ate their protein and vegetables before their carbohydrates, their peak blood sugar rise dropped by more than 40% (Shukla et al., 2019). A similar effect was seen in healthy adults (Sun et al., 2019).
• Adding nuts to a carb-heavy meal (white bread) lowered the blood sugar response, and the more nuts, the bigger the effect (Kendall et al., 2011).

So while oats aren't "only good with protein," pairing them with protein and healthy fat is one of the easiest ways to make your bowl even more blood-sugar-friendly.

What about sweetening it? Why I reach for real maple syrup

Oatmeal can taste a little plain, and I'm not going to tell you to eat it that way forever. If you want some sweetness, my pick is a small amount of pure maple syrup. Not "pancake syrup," which is usually corn syrup with maple flavoring.

Here's why. In a small, well-designed study (randomized and double-blind), adults with mild metabolic changes swapped some of the refined sugar in their diet for maple syrup for 8 weeks. Compared with a plain sugar syrup, the maple syrup group had a better blood sugar response on a glucose tolerance test, a small drop in belly fat, and slightly lower systolic blood pressure (Morissette et al., 2024). Researchers think maple syrup's natural plant compounds (polyphenols) may play a role. (In the interest of transparency: this study was funded in part by Quebec's maple syrup producers' association. The authors report that the funders had no role in designing the study or analyzing the results.)

One important caveat: maple syrup is still sugar. That was one small study, and the differences were modest. Think of it as a better swap for refined sugar, not a health food. A teaspoon or two is plenty.

How I'd build a blood-sugar-friendly bowl

• Choose steel-cut or old-fashioned oats. Skip the instant packets.
• Watch your portion. About ½ cup dry is a reasonable starting serving for most people.
• Add protein: Greek yogurt on the side, a scoop of protein powder (stir it in after cooking for a smoother, less clumpy texture), or eggs alongside.
• Add healthy fat and extra fiber: a spoonful of nut butter, chopped walnuts or almonds, chia seeds, or ground flax.
• Add color: berries are naturally sweet and packed with fiber.
• Sweeten lightly, if at all: 1–2 teaspoons of pure maple syrup, or a sprinkle of cinnamon.

The bottom line

Oats aren't the blood sugar villain they're sometimes made out to be. Choosing less-processed oats, keeping portions sensible, and pairing them with protein and healthy fat can turn oatmeal into a breakfast that supports steadier energy.

Everyone responds a little differently, though. If you wear a continuous glucose monitor (CGM), your own numbers after a bowl of oatmeal will tell you more than any study can. And if you're working on your blood sugar, weight, or metabolic health, I'd love to help you build a plan that fits your body and your labs.

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Diane Lietz, MSN, APRN, FNP-C
VGM Health

This article is for educational purposes only and isn't a substitute for personalized medical advice. If you have diabetes or take medication that lowers blood sugar, talk with your healthcare provider before making changes to your diet.

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References

1. Tosh SM, Chu Y. Systematic review of the effect of processing of whole-grain oat cereals on glycaemic response. Br J Nutr. 2015;114(8):1256–62. https://doi.org/10.1017/S0007114515002895
2. Zurbau A, Noronha JC, Khan TA, Sievenpiper JL, Wolever TMS. The effect of oat β-glucan on postprandial blood glucose and insulin responses: a systematic review and meta-analysis. Eur J Clin Nutr. 2021;75(11):1540–54. https://doi.org/10.1038/s41430-021-00875-9
3. He LX, Zhao J, Huang YS, Li Y. The difference between oats and beta-glucan extract intake in the management of HbA1c, fasting glucose and insulin sensitivity: a meta-analysis of randomized controlled trials. Food Funct. 2016;7(3):1413–28. https://doi.org/10.1039/c5fo01364j
4. Shen XL, et al. Effect of oat β-glucan intake on glycaemic control and insulin sensitivity of diabetic patients: a meta-analysis of randomized controlled trials. Nutrients. 2016;8(1):39. https://doi.org/10.3390/nu8010039
5. Shukla AP, et al. The impact of food order on postprandial glycaemic excursions in prediabetes. Diabetes Obes Metab. 2019;21(2):377–81. https://doi.org/10.1111/dom.13503
6. Sun L, et al. Postprandial glucose, insulin and incretin responses differ by test meal macronutrient ingestion sequence (PATTERN study). Clin Nutr. 2020;39(3):950–7. https://doi.org/10.1016/j.clnu.2019.04.001
7. Kendall CWC, et al. The glycemic effect of nut-enriched meals in healthy and diabetic subjects. Nutr Metab Cardiovasc Dis. 2011;21 Suppl 1:S34–9. https://doi.org/10.1016/j.numecd.2011.03.013
8. Morissette A, et al. Substituting refined sugars with maple syrup decreases key cardiometabolic risk factors in individuals with mild metabolic alterations: a randomized, double-blind, controlled crossover trial. J Nutr. 2024;154(10):2963–75. https://doi.org/10.1016/j.tjnut.2024.08.014

Diane Lietz, MSN, APRN, FNP-C is the founder and sole clinician at VGM Health in Springfield, IL. She offers in-person and telehealth care throughout Illinois.