Helsa Health

    Oats & breakfast cereals · Glycemic index

    Do cornflakes spike blood sugar?

    Moderately. Cornflakes have a high GI of 80, and a 30 g serving (1 cup) has a medium glycemic load of 18. Cornflakes are toasted flakes of refined corn with little fiber, and they have one of the highest average GIs among breakfast cereals.

    Key numbers

    Glycemic index
    80
    High GI
    Glycemic load
    18
    Medium GL
    Available carbs
    23 g
    1.1 g fiber
    Serving
    1 cup
    30 g · ready-to-eat

    GI vs GL for cornflakes

    The glycemic index (GI) compares how fast the carbohydrate in a food raises blood sugar against pure glucose (100), using a fixed amount of carbohydrate. The glycemic load (GL) adds the other half of the story — how much carbohydrate a normal serving actually contains: GI × available carbs Ă· 100. For cornflakes: 80 × 23 g Ă· 100 ≈ 18.

    That figure is an average reported in the 2021 international GI tables (“Cornflakes, mean of 10 foods”). Cornflakes have tested consistently high: five studies in the 2008 tables averaged 81.

    Eating a different amount? Work out the glycemic load of your portion.

    How to eat cornflakes with less of a spike

    • Treat one cup as the whole carbohydrate portion of breakfast and skip toast or juice alongside it.
    • Build a Diabetes-Plate style breakfast: a smaller bowl of cereal plus protein such as eggs or Greek yogurt.
    • If you like the crunch, try a little granola instead — its average GI is far lower.

    Lower-GI swaps

    Compare with

    See all 67 foods in the glycemic index table

    Frequently asked questions

    What is the glycemic index of cornflakes?

    Cornflakes have a glycemic index of 80, which is high. That figure is an average reported in the 2021 international GI tables (“Cornflakes, mean of 10 foods”). A 30 g serving (1 cup) contains about 23 g of available carbohydrate, giving a glycemic load of 18 (medium).

    Is cornflakes good for prediabetes?

    Cornflakes are one of the weaker breakfast choices for prediabetes because they raise blood sugar quickly. Oat-based cereals, granola in small amounts or a savory breakfast are better everyday picks.

    Do cornflakes raise blood sugar more than white bread?

    Slightly, on GI: cornflakes averaged 80 and white bread 73 in the 2021 tables. A 1-cup bowl of cornflakes also carries more carbohydrate than a single slice of white bread.

    Sources

    GI values come from the international GI tables; carbohydrate and fiber per serving are calculated from USDA FoodData Central.

    1. Atkinson FS, Brand-Miller JC, Foster-Powell K, Buyken AE, Goletzke J. International tables of glycemic index and glycemic load values 2021: a systematic review. Am J Clin Nutr. 2021;114(5):1625–1632, Supplemental Table 1
    2. USDA FoodData Central, FDC ID 2708453: Cereal, corn flakes, plain
    3. Atkinson FS, Foster-Powell K, Brand-Miller JC. International tables of glycemic index and glycemic load values: 2008 — online appendix, Table A1
    4. American Diabetes Association, Diabetes Food Hub — Create-Your-Plate: Simplify Meal Planning with the Diabetes Plate
    5. USDA FoodData Central, FDC ID 174924: Bread, white, commercially prepared (includes soft bread crumbs)

    Data last checked .

    Real meals aren’t single foods

    GI tables measure one food eaten on its own. Helsa’s photo and voice meal logging uses AI nutrition analysis to estimate how a whole meal — the rice with the curry, the toast with the eggs — is likely to affect your blood sugar, with no CGM needed. Helsa is free to download, with optional premium features.

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