Quick answer: There's no good evidence that bananas cause constipation. The idea mostly comes from what people believe: in a German survey, bananas were among the foods most often blamed. Bananas contain fiber, and NIDDK lists fruit as part of a constipation-friendly diet. Green, firm bananas are higher in resistant starch, and ripe ones are higher in fructans, which can bother some people with IBS. If you suspect bananas, test ripe vs. green over a week each.
Bananas get blamed for constipation constantly. They also get recommended for constipation constantly. Both camps can't be fully right. The honest answer is that research on bananas and bowel habits in adults is surprisingly thin. Most of what's written online is opinion stacked on opinion.
Here's what's actually known, why ripeness matters, and how to find out whether bananas affect you.
Key takeaways
- The "bananas constipate you" idea is backed by surveys of belief, not controlled trials in adults [1].
- Bananas change as they ripen: starch drops and sugars rise [2]. Ripe bananas carry more fructans, a FODMAP [3].
- The only randomized trial we found used green banana biomass, in children, and it suggested benefit, not harm [4].
- Fruit in general, and kiwifruit specifically, has better trial evidence for constipation than bananas do [5].
- A one-week ripe vs. green comparison, with stool types logged, tells you more than any article can.
Do bananas cause constipation?
Not according to any controlled evidence we could find. The belief, though, is real and widespread.
In a 2005 German questionnaire study, 200 healthy people, 122 with chronic constipation and 766 with IBS-C were asked which foods changed their stool. When asked directly, 29–48% said bananas were constipating. Only chocolate was blamed more often [1]. The same study found that people with constipation reported food effects more often than healthy controls [1].
That's the key limitation. The study measured what people perceived, not what bananas did to their stool [1]. A food can earn a reputation simply because it's eaten when you're already unwell, or alongside other low-fiber foods.
We found no adult trial showing that ordinary banana intake causes constipation.
Are green bananas or ripe bananas more constipating?
Neither has been shown to cause constipation. They do behave differently in the gut, though, so it's reasonable that people react differently.
Green (firm) bananas are starchier. As a banana ripens, its starch breaks down and sucrose increases [2]. Much of the starch in unripe bananas is resistant starch, which escapes digestion in the small intestine and reaches the colon [4]. Resistant starch is often described as "binding." That's an online claim, not a trial finding: the one trial of green banana biomass suggested it helped constipation in children [4].
Ripe bananas are sweeter and, per Monash University's testing, higher in fructans (oligo-fructans). Monash rates ripe banana as high-FODMAP and firm banana as low-FODMAP at a standard serve. A smaller serve of ripe banana, about one-third of a banana, is listed as tolerable [3]. Fructans don't cause constipation in themselves. In people with IBS, though, FODMAPs can trigger bloating and discomfort, which can feel like being "backed up."
| Green / firm banana | Ripe / spotty banana | |
|---|---|---|
| Main carbohydrate | More starch, including resistant starch [2][4] | More sugars; starch largely broken down [2] |
| FODMAP rating (Monash) | Low at a standard serve [3] | High (fructans); about ⅓ banana is low [3] |
| Constipation evidence | One pediatric trial suggested benefit [4] | No trial evidence either way |
| Who might notice it | People sensitive to starchy, filling foods | People with IBS who react to fructans |
If you have IBS, our guide to IBS trigger foods explains how FODMAPs fit in.
Are bananas good for constipation?
They're a reasonable part of a constipation-friendly diet, but they're not a proven treatment.
NIDDK recommends fruit as part of eating more fiber for constipation [6]. In a 2023 meta-analysis of food trials in adults with chronic constipation, fruits increased stool frequency compared with psyllium. Kiwifruit drove most of that effect [5]. Bananas weren't among the fruits tested [5].
The green banana trial is the closest thing to direct evidence. In 80 children and adolescents with functional constipation, two tablespoons a day of green banana biomass, alone or with laxatives, was linked to improvement. It also helped reduce the laxative doses needed [4]. That's children, a processed form of green banana and one small trial. It's encouraging, not conclusive.
If you want the best-supported foods, kiwifruit and rye bread have more trial evidence than bananas [5]. For fiber supplements and when fiber backfires, see can fiber make constipation worse.
Why do some people get diarrhea after bananas?
It's less common, but some people do notice looser stools. In people with IBS, a large serve of ripe banana is high in fructans [3], and FODMAPs can trigger symptoms including diarrhea in some people. A true banana allergy is a different issue and usually involves symptoms beyond the gut. If you get hives, swelling or breathing problems after bananas, that needs prompt medical attention.
How to test bananas on yourself
Compare a week with your usual bananas to a week with a different ripeness, or none. Keep everything else the same.
- Week 1 (baseline): Eat bananas as you usually do and note their ripeness (green, yellow, spotty). Log every bowel movement with its Bristol type, plus no-go days.
- Week 2 (one change): Change only the banana variable. Switch ripeness, or swap bananas for another fruit like kiwifruit.
- Compare: bowel movements per week, share of hard stools (type 1–2), and bloating.
- Look a day ahead. Effects on stool usually show up over the next day or two, not within the hour. Compare next-day stool after banana days with next-day stool after banana-free days.
Illustrative example: ripe vs. green week
This is an illustrative example, not real user data.
| Day | Banana | Next-day BM? | Bristol type | Bloating (0–3) |
|---|---|---|---|---|
| Mon | 1 ripe | Yes | 4 | 1 |
| Tue | 1 ripe | Yes | 4 | 2 |
| Wed | None | Yes | 3 | 0 |
| Thu | 1 green | No | — | 0 |
| Fri | 1 green | Yes | 2 | 0 |
| Sat | None | Yes | 3 | 0 |
| Sun | 1 green | No | — | 0 |
Reading it: in this made-up week, green-banana days were followed by fewer and harder stools, while ripe-banana days came with a bit more bloating. That's a possible pattern worth repeating, not proof. One week is a small sample, and fiber, fluids and sleep also shift day to day.
How to track this
To link a food to your bowels, you need food and stool in the same timeline, with times. Record:
- The food and a quick descriptor ("banana, green")
- Each bowel movement: time, Bristol type, straining
- No-go days, marked clearly
- Bloating or discomfort, 0–3
Our constipation diary guide has a printable version. The same method works for other suspects. See our take on whether cheese causes constipation.
For ongoing records, explore the Get Regular poop tracker. Compare the current logging workflow and access with the details you want to keep. An app record does not identify the cause of a bowel change.
When to see a doctor
A banana is unlikely to be behind a real change in your bowels. Get checked if you have:
- Blood in or on your stool, or black, tarry stool
- Unintended weight loss
- New, persistent constipation, especially if you're over 50
- Severe belly pain, vomiting, a swollen belly or being unable to pass gas. Seek urgent care, as these can signal a blockage [7].
- Constipation alternating with thin stools, or any lasting change in bowel habit
- Constipation that doesn't improve with self-care, or a family history of colon or rectal cancer [7]
More detail: when to see a doctor about bowel changes.
FAQ
Can bananas constipate babies?
We didn't find good evidence that bananas constipate infants. Babies' bowel habits vary widely. If your baby has hard, painful stools or you're worried, ask your pediatrician before changing their diet.
How many bananas a day is too many for constipation?
There's no research-based limit. If you have IBS, Monash rates a ripe banana as high-FODMAP at a full serve, with about one-third of a banana listed as low-FODMAP [3]. For most people, variety matters more than a banana count.
Do bananas help you poop?
They may contribute fiber and fruit to your diet, which NIDDK recommends for constipation [6]. Kiwifruit has better trial evidence for increasing bowel movements [5].
Why do people say bananas are binding?
Partly reputation. In a German survey, bananas were among the foods most often perceived as constipating [1]. Green bananas' resistant starch may add to the idea, though the one trial we found suggested green banana biomass helped constipation in children [4].
Sources
- Müller-Lissner SA, Kaatz V, Brandt W, Keller J, Layer P. The perceived effect of various foods and beverages on stool consistency. Eur J Gastroenterol Hepatol. 2005;17(1):109–112. https://pubmed.ncbi.nlm.nih.gov/15647650/
- The Properties, Modification, and Application of Banana Starch (review). Polymers. 2022. https://pmc.ncbi.nlm.nih.gov/articles/PMC9370678/
- Monash University FODMAP. Bananas and FODMAPs (blog, 16 May 2017). https://www.monashfodmap.com/blog/update-bananas-re-tested/
- Cassettari VMG, et al. Combinations of laxatives and green banana biomass on the treatment of functional constipation in children and adolescents: a randomized study. J Pediatr (Rio J). 2019;95(1):27–33. https://www.scielo.br/j/jped/a/v6ZsWYz7MKCmQT5b4SbLr3s/?lang=pt
- van der Schoot A, Katsirma Z, Whelan K, Dimidi E. Systematic review and meta-analysis: Foods, drinks and diets and their effect on chronic constipation in adults. Aliment Pharmacol Ther. 2023. https://onlinelibrary.wiley.com/doi/10.1111/apt.17782
- NIDDK. Eating, Diet, & Nutrition for Constipation. https://www.niddk.nih.gov/health-information/digestive-diseases/constipation/eating-diet-nutrition
- NIDDK. Symptoms & Causes of Constipation. https://www.niddk.nih.gov/health-information/digestive-diseases/constipation/symptoms-causes
This article is for general education and isn't medical advice. Get Regular is a tracking app — it doesn't diagnose or treat any condition. If you have red-flag symptoms or ongoing changes in your digestion, talk to a doctor.