Kiwi, papaya and pineapple enzymes: what the research says

A plate of fruit after a heavy meal sounds like an old-fashioned remedy. But a few fruits contain enzymes that break down protein, and that has made them a real subject of digestive research. Green kiwifruit contains actinidin, papaya contains papain, and pineapple contains bromelain.

Does eating these fruits, or taking their enzymes as supplements, actually help digestion? Here's what human studies show, fruit by fruit.

Green kiwifruit: the most studied

Protein digestion. In a small randomized crossover trial, 12 healthy older adults ate 2 kiwifruits a day for 14 days before a test meal of beef, once with green kiwifruit, which contains actinidin, and once with gold kiwifruit, which doesn't. With green kiwifruit, essential amino acids showed up in the blood faster. But the total amount absorbed was the same, and measures of protein metabolism didn't differ (Park et al., 2021).

Comfort after a big protein meal. In a pilot trial, 10 healthy men ate a 400-gram steak with either 2 green or 2 gold kiwifruits. Stomach emptying and transit times didn't differ, but bloating was significantly lower with green kiwifruit (Wallace et al., 2017).

Upper digestive symptoms. A scoping review of 12 clinical trials with 661 participants found good evidence that green kiwifruit may reduce abdominal discomfort and pain, and some evidence that it may ease indigestion. Upper digestive symptoms were secondary outcomes in these trials, many of which focused on constipation (Bayer et al., 2022).

Constipation. In an international multicenter trial, people with functional constipation or IBS with constipation, along with healthy controls, ate 2 green kiwifruits a day or took 7.5 grams of psyllium, each for 4 weeks. Kiwifruit increased complete spontaneous bowel movements by about 1.5 or more per week in the constipated groups and improved their digestive comfort scores (Gearry et al., 2023).

One caveat: kiwifruit also contains fiber and other compounds, so not every benefit can be credited to actinidin. The comparisons of green and gold kiwifruit get closest to isolating the enzyme, and they're very small.

Papaya: a single trial

A double-blind, placebo-controlled study tested a papaya preparation, 20 ml a day for 40 days, in volunteers with chronic indigestion and other digestive complaints. Constipation and bloating improved significantly in the papaya group. Heartburn fell short of significance because few participants had it. None of the benefits were still present after a washout period without the product (Muss et al., 2013).

That's one study of one specific product, so it's a starting point rather than proof.

Pineapple: popular, but untested for this

Bromelain, the enzyme mixture from pineapple, is often marketed as a digestive aid. When we searched PubMed, we didn't find controlled human trials testing bromelain for everyday indigestion or bloating. That doesn't mean it can't help. It means there's no good human evidence yet either way.

What this adds up to

• Kiwifruit has the most support, mainly for constipation and digestive comfort, with early, small studies on protein digestion and bloating after a protein-heavy meal.
• Papaya has one encouraging but limited trial.
• Pineapple enzymes haven't been properly tested for this purpose in people.
• All three enzymes work on protein. They don't break down fat, lactose or the gas-producing carbohydrates in beans, so they cover only one part of digestion.

Fruit or capsule?

Most of the kiwifruit research used whole, fresh green kiwifruit, and the papaya trial tested one specific liquid preparation. Capsules and powders sold with kiwi, papaya or pineapple enzymes weren't what these studies measured, and products can differ in how much active enzyme they contain. If you want to follow the evidence as closely as possible, start with the whole fruit, which also gives you its fiber.

How to test it yourself

1. Choose one approach, such as 2 green kiwifruits a day, and stick with it for 4 weeks.
2. Keep the rest of your routine the same.
3. Twice a week, rate post-meal heaviness, bloating and bowel habits from 0 to 10.
4. Compare your first week with your fourth.

Whole fruit is inexpensive and easy to add to breakfast or dessert, which makes it a low-risk experiment for most people. Skip it if you have a known allergy to the fruit.

When fruit isn't the answer

If heaviness after meals comes with weight loss, trouble swallowing, repeated vomiting, black or bloody stools, or greasy stools that are hard to flush, see a doctor rather than experimenting with foods or supplements.

Sources

1. Park S, Church DD, Starck C, et al. The impact of Hayward green kiwifruit on dietary protein digestion and protein metabolism. Eur J Nutr. 2021;60(2):1141-1148. PMID 32970234
2. Wallace A, Eady S, Drummond L, Hedderley D, Ansell J, Gearry R. A pilot randomized cross-over trial to examine the effect of kiwifruit on satiety and measures of gastric comfort in healthy adult males. Nutrients. 2017;9(7):639. PMID 28640214
3. Bayer SB, Frampton CM, Gearry RB, Barbara G. Habitual green kiwifruit consumption is associated with a reduction in upper gastrointestinal symptoms: a systematic scoping review. Adv Nutr. 2022;13(3):846-856. PMID 35266507
4. Gearry R, Fukudo S, Barbara G, et al. Consumption of 2 green kiwifruits daily improves constipation and abdominal comfort: results of an international multicenter randomized controlled trial. Am J Gastroenterol. 2023;118(6):1058-1068. PMID 36537785
5. Muss C, Mosgoeller W, Endler T. Papaya preparation (Caricol®) in digestive disorders. Neuro Endocrinol Lett. 2013;34(1):38-46. PMID 23524622

This article is for general information and isn't medical advice. Talk to your healthcare provider about ongoing digestive symptoms, and skip any fruit you're allergic to.