Sourdough bread glycemic index
Sourdough bread has a glycemic index of 70, which is high. A 30 g serving (1 slice) has a glycemic load of 10 (low).
Also known as: sourdough
- Serving30 g
- Available carbs15 g
- Fiber0.7 g
- Sugars1.4 g
- Protein3.2 g
- Calories82 kcal
Serving: 1 slice.
What to know
The acids produced during sourdough fermentation can slow digestion, but results vary a lot: white sourdough averaged 70, while sourdough rye and grainy sourdoughs tested lower.
Glycemic load by portion size
GI stays the same whatever you eat, but glycemic load scales with the amount: eating twice as much doubles the effect on blood sugar.
| Amount | Available carbs | Glycemic load | |
|---|---|---|---|
| 50 g | 25 g | 17 | Medium |
| 100 g | 50 g | 35 | High |
| 30 g · 1 slice | 15 g | 10 | Low |
| 60 g · double serving | 30 g | 21 | High |
What the studies found
The value of 70 is the mean calculated by the authors of the International Tables of Glycemic Index (2021) across 5 studies. Results are fairly consistent (54 to 70).
Each dot is one study. Green dots followed the ISO 26642 standard method.
- 54 · Australia 2003
- 55 · Canada 2007
Sourdough bread compared with other bread & bakery
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Frequently asked questions
Is sourdough bread low glycemic?
No. With a GI of 70, sourdough bread is in the high range (70 or more). Low GI is 55 or less.
What is the glycemic load of sourdough bread?
A 30 g serving (1 slice) has a glycemic load of 10, which is low. Glycemic load combines GI with the amount of carbohydrate in the portion: 10 or less is low, 11 to 19 medium and 20 or more high.
Can people with diabetes eat sourdough bread?
With a GI of 70 and a low glycemic load per serving, sourdough bread usually fits a diabetes-friendly diet in normal portions. Everyone responds differently, so talk to your doctor or dietitian about your plan.
How many carbs are in sourdough bread?
A 30 g serving has about 16 g of total carbohydrate, including 0.7 g of fiber, leaving 14.9 g of available carbohydrate (the part that raises blood sugar). Per 100 g: 51.9 g of carbohydrate.
Nutrition facts
| per 100 g | Serving (30 g) | |
|---|---|---|
| Calories | 272 kcal | 82 kcal |
| Carbohydrates | 52 g | 16 g |
| Available carbs | 50 g | 15 g |
| Fiber | 2.2 g | 0.7 g |
| Sugars | 4.6 g | 1.4 g |
| Protein | 11 g | 3.2 g |
| Fat | 2.4 g | 0.7 g |
Source: USDA FoodData Central, Bread, french or vienna (includes sourdough) (SR Legacy, FDC 172675). Available carbohydrate = total carbohydrate minus fiber.
Sources: 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. USDA FoodData Central. How we calculate each value: Methodology & sources.
Data last reviewed 2026-09-29.