- Green bananas are higher in prebiotic fiber, which supports gut health and satiety.
- Ripe bananas are sweet, easy to digest and still provide steady energy and key nutrients.
- Enjoy unripened bananas with yogurt and nut butters or add them to smoothies.
Bananas change in flavor and appearance as they ripen. But do they change in their nutritional constitution? As they go from green and firm to yellow and soft, do they lose some of their fiber content? Not exactly.
“[A banana] doesn’t lose fiber, but the fiber changes as the banana matures. It goes from having more to less resistant starch,” says Monica Auslander Moreno, M.S., RD, LDN. That’s why you may have heard that a green, less-ripe banana is better for you. Let’s break it down.
Why Resistant Starch Is Good for You
Resistant starch is a type of prebiotic fiber mostly found in foods like grains, potatoes, bananas and beans. As the name implies, these starches resist being broken down in your digestive tract. This allows them to remain intact until they reach the large intestine, where they can be used as fuel for the good bacteria in our gut. Resistant starch, which has five different subgroups, interests researchers because it may help reduce the incidence of inflammatory bowel diseases, like ulcerative colitis and Crohn’s disease, as well as colon cancer.
Research indicates that consuming resistant starch might play a role in reducing inflammation in the body in general. This could be helpful for a variety of chronic conditions, including cardiovascular disease, nonalcoholic fatty liver disease, type 2 diabetes, obesity and metabolic syndrome, although further investigation is warranted.
What Happens as They Ripen
As a banana ripens, the structure of its carbohydrates breaks down from prebiotic fibers and pectin to sugar. For example, a fully green banana contains more than 3 grams of fiber, while an overripe banana possesses less than 2 grams of fiber. The amount of total carbohydrates in a banana remains consistent, regardless of its ripeness level. But the change in fiber content can be attributed to the transformation of its carbohydrates as it ripens. The values of other nutrients, such as potassium, vitamin C, protein and fat, remain consistent at any stage of ripeness.
Another thing that changes as a banana ripens: its satiety factor. This means that eating a ripe banana versus eating a greener banana can have different effects on your appetite. Moreno says, “A super-ripe banana is perfect for baking. But unless you’re baking with them, I recommend the more underripe bananas to harness more of that prebiotic fiber.” Prebiotic fiber has a filling effect, making you feel more satisfied for longer. That said, the flavor of completely green bananas may not be as appetizing as that of ripe bananas, so aim for a happy medium. If a banana is getting past its prime, it might be better suited for banana bread than for an afternoon snack.
Blood Sugar Control
While the sugar content of a banana may seem high, the glycemic index of ripe bananas is actually rated low at 51, with slightly underripe fruit (think: yellow with some green sections) scoring even lower at 42. This means that bananas will help keep your blood sugar levels more consistent (compared to higher-GI foods), while avoiding large spikes and crashes. This could be due to the amount of resistant starch in the fruit, which moves through the small intestine without much absorption into the bloodstream. Bananas, therefore, are a good food choice for people with diabetes or others trying to watch their blood sugar levels.
Enjoy Unripened Bananas
If you’re new to eating underripe bananas, here are some easy ways to include them in your day:
Our Expert Take
Many of us may think that bananas should be completely yellow by the time we eat them, but greener bananas may offer more fiber than riper bananas. Still, bananas are healthy and safe to eat at any stage of their development. The next time you reach for one, remember that a banana that’s a little green might have slightly more gut-friendly fiber than one that’s completely ripe or overripe.
