Adding just two juicy kiwifruit to your daily routine could be the sweet, tangy secret to smoother digestion and more regular bathroom visits. Photo / Getty Images
Kiwifruit can boost your gut health. They may also lower triglycerides and cancer risk.
Is there something I can eat to help with constipation? A lot of high-fibre foods and supplements make me bloated, but I don’t want to take a laxative.
I get this question often in my gastroenterology clinic. Gut symptoms like bloating and constipation are incredibly common, affecting up to a third of the population. Many people don’t want to take medication if there are more natural ways to help. But I also know that simply recommending people increase their fibre intake is vague and not always useful.
That’s why I’ve been “prescribing” a dose of two kiwifruit a day to my patients for years now.
A small but mighty green or gold fruit, kiwifruit are bursting with nutrients: a single kiwifruit contains 80% or more of an adult’s daily vitamin C requirement and packs two to four grams of fibre. In addition to vitamins E and K and other beneficial antioxidants and phytochemicals, one of the kiwi’s most important properties is an enzyme called actinidin.
Actinidin is present in only a few dietary sources besides kiwifruit (including mango and pineapple), and it can help break down proteins, aiding in our digestion. Actinidin is so powerful that it’s used commercially as a meat tenderiser.
So how does this help your gut? Let me fill you in on the findings of a randomised controlled trial that electrified gastroenterologists everywhere. The study was funded by a kiwifruit marketer, but its methods were rigorous and showed clear measurable outcomes.
In the 2022 study, scientists from three countries – New Zealand, Italy and Japan – found that eating two green kiwifruit per day for four weeks helped people have more complete bowel movements. On average, people pooped between one and two more times each week.
For people with constipation at baseline, kiwifruit improved symptoms such as abdominal pain, indigestion and straining during bowel movements – often even more so than psyllium, a type of fibre sold in powders and capsules over-the-counter. These people also reported an improvement in overall quality of life.
Consuming a diversity of plants is always the overarching goal for a healthy microbiome, and I tell patients that kiwifruit can be a great addition to that approach. I’ve seen the benefits firsthand in my patients and even my own family.
Besides fibre, the benefits of eating a diet rich in vegetables and fruits like kiwifruit are commonly attributed to their antioxidants. These compounds are known to protect against cancer, cardiovascular diseases and diabetes.
But – and this is a big one – it’s an effect that mainly appears to occur through a healthy diet – and not through antioxidant supplementation.
As is often the case with other supplements, when you try to distil the compound of interest into a capsule or pill, that beneficial health effect of antioxidants vanishes – and may even be potentially harmful.
Scientists suspect that the kiwi’s antioxidants, like vitamin C, synergise with its other naturally occurring phytochemicals to boost its protective power – something we lose when we distil these nutrients into a commercialised supplement.
In 2011, Norwegian researchers randomised healthy volunteers to a month of eating either one or two gold kiwifruit daily. When the scientists analysed DNA samples, they found fewer DNA strand breaks – a sign of improved fortitude that can theoretically reduce opportunities for cancerous growth.
And indeed, after one month, the volunteers’ DNA had become about 30% more resistant to a kind of injury called oxidative damage that can lead to dangerous mutations.
Besides studying DNA, researchers also looked at plasma triglycerides, a kind of fat circulating in the bloodstream that increases heart attack risk. At the end of the month, triglycerides had decreased by about 13%.
Though not a perfect study design, a 2023 meta-analysis of retrospective studies of kiwi and other fruit consumption found that people who ate more kiwis had a 13% decreased risk of colorectal cancer.
More research needs to be done to fully understand kiwifruit consumption and cancer risk – but the scientific groundwork has been laid.
Supplementing with psyllium husk fibre has long reigned as queen in the gastroenterology world: psyllium is specific, easy to take and does wonders for the body.
Prunes have been hailed for their laxative properties, but, if I’m being honest, have you ever tried to tell a college student with constipation to go buy some prunes? Trust me, it won’t happen. And for many people, prunes can actually make bloating worse because of high levels of sorbitol, a naturally occurring sugar that gets fermented by your colon’s microbiome. That’s why I tend to recommend kiwis instead.
No, you don’t have to eat the kiwi’s peel. Plenty of studies have found notable health benefits sans peel. But if you feel so inclined, go on, have a little nibble on the skin. It’s totally edible and packed with fibre. Just be sure to keep your doctor in the loop about your gut issues.
For lots of people, the underlying condition causing their symptoms is past the point of a simpler dietary intervention. It’s why it’s important to find a doctor you trust who can consider multiple angles in approaching your health concerns.
Trisha Pasricha is a physician and journalist who writes the Ask a Doctor column for The Washington Post. She is an instructor in medicine at Harvard Medical School and author of the forthcoming You’ve Been Pooping All Wrong.