FODMAP and Food Processing Series
In this installment of my FODMAP and Food Processing series, I’ll focus on how and why dehydration, ripening and storage conditions affect the FODMAP content in fruit. Future articles will address how fermentation and other processing methods can make a particular food tolerable or torturous for sensitive tummies.
Anyone familiar with the Monash University Low FODMAP Diet Smartphone App has doubtless found themselves wondering why some fruits get a Green Light when they’re in one form, and a Red Light when they’re in another. The reason for this is that the FODMAP content in plant foods is affected by storage time and temperature, water content, and ripeness among other things. Because of this, fruits such as grapes and their dehydrated counterpart — raisins — have to be individually analyzed for FODMAP content; it’s not enough to test one and assume the same results for the other. Accordingly, the items I will be discussing have been subjected to laboratory analysis — just like all foods found in the Monash App.
A Grape’s Defense Mechanism
Grapes and raisins were my gateway into the world of weird FODMAP science, but the main reasons grapes get a Green Light rating and raisins a Red are quite straightforward: a) we tend to eat more raisins than grapes because they’re so much smaller b) removing the liquid from high water content items such as fruit shrinks the overall volume of the food and concentrates all its other components. In the case of grapes, one of the “other components” is oligos-fructans, i.e., the “O” in FODMAP.
The weird science part of why raisins are higher in FODMAPs than grapes has to do with the fact that the dehydration process actually increases their overall fructan content. Apparently, the same goes for fresh pineapple and papaya (paw paw in the Monash App) and the dried versions of these fruits.
The closest I could get to an explanation for why this might occur was a 2003 study showing that fructans help preserve a plants membrane barrier during dehydration. Presumably, as the water content in grapes (and pineapple and papaya) decreases, the fruit generates fructans as a way to defend itself. Too bad humans can’t do the same thing − our skin only gets more fragile the drier it gets!
Bananas Also Defend Themselves
Bananas are another head-scratcher in the fruit category. I’ve been helping people navigate the low FODMAP diet long enough to have seen the common banana go from low FODMAP to high, and then somewhere in between. This popular fruit is a great example of how environmental factors can influence a food’s FODMAP content.
Similar to grapes, bananas accumulate fructans as protection when their environment stresses them out. Cold weather is just such a stressor. While a cold climate is not typical of the tropics, where bananas come from, it is typical of the environment in which bananas are stored and ripened. The longer a banana spends ripening in cold storage, the higher its fructan content. This means that if you’re sensitive to fructans, you may need to limit yourself to a measly 1/3 of a medium ripe common banana, i.e., the amount listed as low in FODMAPs in the Monash Smartphone App. Better yet, why not incorporate bananas into recipes like we did in these:
Before you assume all unripe fruit is lower in FODMAPs, consider the guava. According to a 2016 report from Monash University, ripe guava contains little to no FODMAPs, while the unripe fruit is a fructose nightmare. Why? I don’t know, but I’ll keep you posted as more information becomes available!
When in doubt, check the Monash University app for the most comprehensive and current information about your favorite foods. If there’s anything I’ve learned in my years of working with this diet, it’s that things don’t always seem to make sense in the FODMAP universe! Here at FODMAP Everyday® we strive to bring you information that we hope makes navigating this diet a little bit easier and a whole lot more delicious!
Want to learn more? Read our next articles in this series:
Ingrid J. Vereyken, Vladimir Chupin, Folkert A. Hoekstra, Sjef C. M. Smeekens, and Ben de Kruijff. The Effect of Fructan on Membrane Lipid Organization and Dynamics in the Dry State (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1302958) Biophys J. 2003 Jun; 84(6): 3759–3766.
Update: Bananas Re-Tested! (https://www.monashfodmap.com/blog/update-bananas-re-tested). May 16, 2017. Citation from Monashfodmap.com.
UPDATE! Newly tested foods: the mysterious case of the guava (https://www.monashfodmap.com/blog/guava-recipes). March 22, 2016. Citation from Monashfodmap.com