Introduction
Green bananas are the unripened version of the popular fruit. Unlike ripe bananas that are sweet and soft, green bananas are firmer and more starchy. That starch is mostly resistant starch – a type of carbohydrate that acts like fibre. Resistant starch passes through the small intestine largely undigested and is fermented in the colon, producing beneficial short‑chain fatty acids. Because of this, green bananas have a much lower glycaemic index (around 42) compared with ripe bananas (around 51)【249625609017337†L209-L218】. Their glycaemic load is also lower, meaning they raise blood sugar more slowly.
Nutrition snapshot
One medium banana contains about 110 calories, 28 g carbohydrates, 15 g natural sugar, 3 g fibre and is rich in potassium and vitamin B6【249625609017337†L120-L123】. When a banana is green, more of those carbohydrates are resistant starch and fibre, and less are sugar【425864655647934†L287-L292】.
Glucose response snapshot
| Banana | Approx. spike (mg/dL) | Why |
|---|---|---|
| Green banana | +15 mg/dL | Low GI (~42), high resistant starch, more fibre |
| Ripe banana | +25 mg/dL | Moderate GI (~51), more sugar and less resistant starch |
| Overripe banana | +30 mg/dL | Higher GI (~57), starch fully converted to sugar【425864655647934†L272-L279】 |
Why green bananas spike less
- Lower glycaemic index & load: Green bananas have a lower GI (≈42) and glycaemic load (≈11) because their starch has not fully converted to sugar【249625609017337†L209-L218】.
- Resistant starch: Much of the carbohydrate in a green banana is resistant starch, which resists digestion in the small intestine and behaves like fibre【425864655647934†L287-L292】. Resistant starch slows glucose absorption and feeds beneficial gut bacteria.
- Higher fibre: Green bananas provide slightly more fibre than ripe bananas, further slowing digestion.
- Nutrient‑dense: They still deliver potassium, vitamin B6 and vitamin C【249625609017337†L120-L123】.
Potential downsides
- Digestive discomfort: The high resistant starch content may cause bloating or gas in some people until their gut adapts.
- Taste & texture: Green bananas are less sweet and firmer than ripe bananas, so some people may not enjoy them.
- Still carbs: Although gentler on blood sugar, they still contain about 28 g of carbohydrates per medium fruit【249625609017337†L120-L123】, so portion size matters.
Tips for enjoying green bananas
- Slice a green banana and add to a smoothie with protein (Greek yogurt) and healthy fats (nut butter) for slower absorption.
- Boil or steam green banana chunks and serve as a savoury side dish.
- If you prefer more sweetness, choose a just‑ripe banana (yellow with some green) to balance resistant starch and flavour.
- Pair with protein or fat such as peanut butter or nuts to further blunt any spike.
Bottom line
Green bananas are a diabetes‑friendly option thanks to their resistant starch and lower glycaemic index. They offer the same essential nutrients as ripe bananas but with a gentler impact on blood sugar. If you’re looking for a portable snack that won’t send your glucose soaring, try a green banana – just be mindful of portion sizes and pair it with protein or healthy fat.
Forever Health 
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