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Quick answer
Eating two green kiwifruit a day is one of the better-studied food approaches for mild, long-lasting constipation in adults. In trials, people who did this for four weeks had slightly more complete bowel movements each week, and in head-to-head comparisons kiwifruit did at least as well as psyllium, a common fibre supplement.
The effect is modest, not dramatic. Most studies were small, short and in people with fairly mild symptoms, so the overall certainty of the evidence is low to moderate. Kiwifruit is cheap, tasty and safe for most people, which makes it a reasonable thing to try alongside the usual advice on fluids, fibre and activity. People with a kiwi or latex allergy should avoid it.
What the research says
The largest trial (2023). Gearry and colleagues ran an international randomised trial in New Zealand, Japan and Italy, published in the American Journal of Gastroenterology. It included 60 adults with functional constipation (long-term constipation without another cause), 61 with irritable bowel syndrome with constipation (IBS-C), and 63 healthy volunteers. Each person ate two peeled green kiwifruit a day for four weeks and, after a four-week break, took 7.5 g of psyllium a day for four weeks, or the same in reverse order.
In the people with constipation, kiwifruit increased complete spontaneous bowel movements by about 1.7 per week, compared with about 0.9 per week for psyllium. Gut symptom scores were also lower with kiwifruit. A review of the trial for the American College of Gastroenterology concluded that two peeled kiwifruit a day appears to be effective, but pointed out important limits: symptoms at the start were very mild, participants knew which treatment they were taking, each phase lasted only four weeks, and the study was funded by a major kiwifruit marketer.
A systematic review (2022). Eltorki and colleagues pooled 7 randomised trials with 399 participants, mostly women with an average age of 42, in the Canadian Journal of Gastroenterology and Hepatology. Compared with psyllium, kiwifruit may add about one extra bowel movement per week (moderate certainty) and may make stools a little softer (low certainty). Kiwifruit or its extracts also reduced abdominal pain compared with placebo. Overall, the reviewers rated the evidence as low certainty and called for larger, better-designed trials.
A professional guideline (2025). The British Dietetic Association published guidelines for the dietary management of chronic constipation in adults (Dimidi and colleagues, Journal of Human Nutrition and Dietetics), based on reviews of 75 randomised trials. Kiwifruit was one of the few foods to earn specific recommendations, along with prunes and rye bread. Most of its recommendations rest on low or very low certainty evidence, and the authors made no recommendations about whole-diet approaches, such as a general high-fibre diet, because there was not enough trial evidence.
How to use it
- Amount: The main trial used two green kiwifruit a day. Studies have not tested whether eating more works better.
- Preparation: In the 2023 trial the fruit was peeled. You can scoop the flesh out with a spoon after cutting the fruit in half.
- Timing: Studies have not shown that a particular time of day works better, so choose whatever is easiest to stick with.
- How long to try: The trials ran for four weeks, and the NHS notes that diet and lifestyle changes can sometimes take a few weeks to make a difference. Give it about a month before deciding whether it helps.
Kiwifruit works best as part of the general advice for constipation. The NHS recommends:
- Increasing fibre gradually, for example with oats, wheat bran or linseed
- Drinking plenty of fluids and avoiding alcohol
- Not delaying when you feel the urge, and keeping a regular toilet routine
- Raising your knees above your hips on the toilet by resting your feet on a low stool
- Moving more, such as a daily walk
MedlinePlus suggests aiming for about 8 to 10 cups (2 to 2.5 litres) of fluid a day, mostly water.
Possible side effects and interactions
For most people, kiwifruit is simply a food and is well tolerated. In the 2022 review, capsules made from kiwifruit extract may have caused more minor side effects than placebo, although that estimate was very uncertain. The trials of whole fruit did not raise safety concerns.
Possible problems include:
- Wind or bloating if you add a lot of fibre at once. MedlinePlus advises adding fibre slowly for this reason.
- Mouth itching or tingling in people with a mild kiwi allergy (see below).
The sources reviewed for this article did not report medicine interactions from eating kiwifruit as a food.
Who should be careful
- People with a kiwi allergy should avoid it. According to an allergen fact sheet from Thermo Fisher, an allergy testing company, kiwi allergy can range from an itchy mouth, scratchy throat or swollen lips (oral allergy syndrome) to hives, vomiting, wheezing or, rarely, anaphylaxis, a life-threatening reaction.
- People with a latex allergy have a higher chance of reacting to kiwi. The same fact sheet notes that 30 to 70% of people with latex allergy also react to certain fruits, including kiwi.
- People with birch pollen hay fever may get mouth and throat itching from raw kiwi.
- People with asthma, especially if it is poorly controlled, may be at higher risk of a severe reaction if they are allergic to kiwi.
- People whose constipation is caused by a medicine, such as opioid painkillers, should speak to their doctor. The NHS advises not to stop any prescribed medicine without talking to your GP first.
When to see a doctor
The NHS advises seeing a GP if:
- Your constipation is not improving with treatment, or keeps coming back
- You are regularly bloated
- You have blood in your poo
- You have lost weight without trying
- You are constipated and feel tired all the time
- You think a medicine is causing it
- Your bowel habits have suddenly changed
- You have tummy pain
MedlinePlus also advises contacting a health professional if you have not had a bowel movement in 3 days, have stomach pain or bloating, or are feeling sick or vomiting.
If diet and lifestyle changes do not help, a pharmacist can recommend a suitable laxative. The NHS notes that laxatives are usually meant for short-term use.
Frequently asked questions
How many kiwis should I eat for constipation?
The most commonly studied amount is two green kiwifruit a day. Studies have not shown that eating more works better, and adding a lot of fibre at once can cause wind and bloating.
How quickly does kiwifruit work?
The NHS says you may notice a difference within a few days of changing your diet, but it can sometimes take a few weeks. The kiwifruit trials measured results after four weeks.
Is kiwifruit better than a fibre supplement?
In trials comparing them directly, kiwifruit increased bowel movements a little more than psyllium and was linked with fewer gut symptoms. The difference was modest, and psyllium is still a reasonable choice. Some people find whole fruit easier to take every day.
Do other fruits help too?
The 2025 British Dietetic Association guidelines also include recommendations for prunes. The NHS suggests fruits that contain sorbitol, a natural sugar that draws water into the bowel, such as apples, apricots, grapes, raspberries and strawberries.
References
- NHS: Constipation
- MedlinePlus: Constipation - self-care
- Thermo Fisher Scientific: Kiwi allergy fact sheet
- American College of Gastroenterology, Evidence-Based GI: Kiwifruit, a specific food to improve stool frequency in mild constipation (review of Gearry et al., Am J Gastroenterol 2023)
- Eltorki M, et al. Kiwifruit and Kiwifruit Extracts for Treatment of Constipation: A Systematic Review and Meta-Analysis. Can J Gastroenterol Hepatol, 2022
- Dimidi E, et al. British Dietetic Association Guidelines for the Dietary Management of Chronic Constipation in Adults. J Hum Nutr Diet, 2025
