Clinical Alimentary

You have heard about prunes haven’t you? I even have a post about prunes here https://clinicalalimentary.blog/2015/09/13/prunes-natures-laxative/ and how they have been used to help with constipation due to their sorbitol content. Sorbitol is a polyol, a sugar that is not absorbed into the body and helps to keep fluid inside the bowel, helping with constipation, but it’s drawback is that it’s a FODMAP. So what if there was a fruit that acted in a similar way to prunes but was low FODMAP? How fantastic that would be – well, kiwi fruit might well be that option.

Some people with IBS with constipation do reduce the fibre that they consume because they have noticed that ‘fruit and vegetables’ can make symptoms worse. The challenge is that there is little data to suggest that the low FODMAP diet resolves constipation in IBS-C, but we should also recognise quality of life and pain and the importance of resolving these outcomes and if pain is reduced but constipation is not then this might be considered an improvement by the person following the diet. We clearly need more research in IBS-C for more treatments to be available in all areas. If the Low Fodmap diet is to be used in IBS-C, in this situation I would always consider patient wishes whilst stating that we know less about IBS-C, and state that the diet must be done for the least amount of time (3 weeks) and if symptoms get worse or do not improve they must stop the diet. Focus needs to be on increasing levels of fibre from foods that are well tolerated in those with IBS and constipation. This is why a dietitian who is knowledgeable about the GI tract can be really beneficial to see to get the balance right. Kiwi fruit would appear to be part of that solution.

For people with constipation in China a study did look at the effects on constipation and found that improvements were seen in transit time (shortened) although this was not a double blind study (the best kind of research study.) For IBS, another study⁴ gave reductions in transit time but again this was not blinded, which might be a problem, but how do you blind a kiwi fruit? This is always a difficult challenge in nutrition. The other problem is the high placebo effects for IBS studies and the decrease in transit time of approximately 20% could possibly be down to a placebo effect. So the science does need to be repeated with better quality studies. The mechanism of why kiwi reduced transit time has been studied⁵ in healthy adults by completing an MRI scan of the bowel and it was found that water content in the bowel was significantly increased and they also suspected that the kiwi showed some action in increasing movement of the bowel (prokinectic action). But we do know that kiwi is low fodmap therefore is less likely to provoke symptoms in people with IBS and there are other potential benefits such as increasing the fibre content of the diet is good for health – so why not give it a try?

Kiwi fruit has 3.0g fibre per 100g so that doesn’t seem a huge amount, for two 6.0¹g. Alternatively prunes have 3.1g per 100g so these figures are very similar. Does the type of fibre matter? It does for people with IBS and if people do respond to a low FODMAP diet then clearly if they have identified polyols as a problem kiwi fruit is an excellent alternative fruit to try to help increase fibre content of the diet. There is also another means of increasing the fibre content and that is to include the skin when you eat one. Yes, you have read this correctly – eat the skin! You might not be relishing that prospect but I do encourage you to give it a try. Wash the kiwi fruit, then trim off the ends and slice it into segments to eat. This is a better means if you are disinclined to give it a try by just eating it whole. Eating the skin will add an additional 1.5g² per 100g therefore a total of 9.0g for two, just under of a third of the daily adult requirements per day!

Are there any people who perhaps should avoid kiwi? Perhaps if people have not tried it before and have been diagnosed with a latex allergy it is possible that kiwi fruit might provoke a reaction as they contain protein that has a very similar structure to latex and the bodies immune system can confuse kiwi for latex. Kiwi can also induce oral symptoms in those with oral allergy syndrome or pollen food syndrome for some people – again due to the protein in kiwi confusing the immune system. But if someone has no symptoms then they can include it in the diet.

1. http://www.nutridata.self.com accessed 27.03.21

2. David P. Richardson · Juliet Ansell · Lynley N. Drummond (2018) The nutritional and health attributes of kiwifruit: a review European Journal of Nutrition (2018) 57:2659–2676

3. Annie On On Chan, Gigi Leung, Teresa Tong, Nina YH Wong (2007) Increasing dietary fiber intake in terms of kiwifruit improves
constipation in Chinese patients World J Gastroenterol 2007 September 21; 13(35): 4771-4775

4. Chang CC, Lin YT, Lu YT, Liu YS, Liu JF. Kiwifruit improves bowel function in patients with irritable bowel syndrome with constipation. Asia Pac J Clin Nutr. 2010;19(4):451-7. PMID: 21147704.

5. Wilkinson-Smith V, Dellschaft N, Ansell J, Hoad C, Marciani L, Gowland P, Spiller R. Mechanisms underlying effects of kiwifruit on intestinal function shown by MRI in healthy volunteers. Aliment Pharmacol Ther. 2019 Mar;49(6):759-768. doi: 10.1111/apt.15127. Epub 2019 Jan 31. PMID: 30706488; PMCID: