You did what everyone tells you to do. You ate the prunes, stirred the fiber powder into a glass of water, and waited. By lunchtime, things were moving a little better, but your jeans felt two sizes too tight and your stomach was rumbling through a meeting.
This is not your fault. The usual advice for constipation, "just eat more fiber," is vague, and the foods that help can come with side effects nobody warns you about. A team of gastroenterologists decided to compare three popular options head to head, and they tracked the bloating, too.
Kiwis, prunes and psyllium, side by side
At Michigan Medicine, a group led by William Chey, a professor of gastroenterology and nutritional sciences, followed 79 adults with chronic constipation for 4 weeks. Each day, participants ate either 2 peeled green kiwis, 100 grams of pitted prunes or 12 grams of psyllium, a fiber supplement. The results were published in the American Journal of Gastroenterology.
All three helped. According to Michigan Medicine, weekly bowel movements roughly doubled with kiwis, more than doubled with psyllium and nearly tripled with prunes. Prunes had the highest response rate (67%), ahead of psyllium (64%) and kiwis (45%), but the difference between the three wasn't statistically significant.
The side effects told a different story. Bloating hit 11% of the kiwi group and 36% of the prune group, which also reported gas and abdominal pain (18% each). In the psyllium group, 33% reported abdominal pain and 19% reported gas. The kiwi group reported no gas or abdominal pain, and it had the highest satisfaction scores.
Choosing your option, one month at a time
The study's doses are a practical starting point:
- Kiwis if bloating is your worry. Eat 2 peeled green kiwis a day. They were the gentlest option in the study.
- Prunes if results come first. Weigh out 100 grams of pitted prunes, about 3.5 ounces, once to learn what a daily portion looks like. They worked best on average, with more side effects.
- Psyllium if fruit isn't practical. The study used 12 grams a day. Follow the label and take it with plenty of water.
- Give it 4 weeks. That's how long participants stuck with each option.
- Keep a simple log. Note bowel movements and bloating each day, so you can judge your own results rather than a single bad morning.
Plan B if none of the three suits you: new constipation guidelines led by researchers at King's College London, published in October 2025, also point to rye bread and high-mineral-content water. They list psyllium supplements, certain strains of probiotics and magnesium oxide supplements as options too. The same review found weak evidence that a generic high-fiber diet helps constipation specifically.
What 79 volunteers can't settle
This was a small trial: 79 people, 87% of them women, and only partially randomized. It lasted 4 weeks, so it says nothing about long-term use. The kiwi research was also partly funded by Zespri, a kiwifruit producer.
Less bloating doesn't mean kiwis work best for everyone. On average, prunes produced the biggest jump in bowel movements, and your body may respond differently than the average participant.
Constipation that lasts for weeks deserves a doctor's visit, especially with blood in the stool, unexplained weight loss or a sudden change in your usual pattern. Ask your doctor or pharmacist before starting psyllium or magnesium oxide if you take other medications or have kidney disease. If kiwi has ever made your mouth itch or swell, skip it.
Two kiwis a day for a month, and a log to see if they work for you. That's the trick.
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