There is a guava tree right in front of my apartment building. The nice thing about this is that, thanks to its strong fragrance, I get a fun, tropical feeling when I walk out the door. The downside, however, is that a lot of rotten fruit falls from the tree and most days I end up with sticky guava mush and peel stuck to the bottoms of my shoes. And the even bigger downside is that the few times I’ve eaten guava recently, I’ve noticed a fast rise in my blood sugar (faster than an apple!), which surprised me. So I decided to do a little guava research to understand why this nutrient-rich fruit (guavas are an excellent source of vitamin C and a good source of vitamin A) with a moderate carbohydrate content was so diabetes-unfriendly. Here’s what I found: In an article from 2007, The Times of India reports, “guava peel can raise your blood sugar.”
A study conducted at the Medicinal Research Laboratory of the University of Allahabad and published in Indian Journal of Medical Research “aimed to determine the glycemic potential of guava fruit peel extract on blood-glucose level of normal and sub-diabetic rats during fasting blood glucose and glucose tolerance test. Blood glucose was measured after collecting the blood from tail veins. The rats showed hyperglycemic effect from a single oral administration of variable doses of guava fruit peel extract.”
For me this raised some questions:
1) How did the researchers come up with the idea of testing guava peel? Never in a million years would I have thought to do anything with guava peel other than eat it, or pick it off the bottom of my shoe (Note: the little seeds in the grooves of the soles of my sneakers are especially annoying.)
2) Until now, I’ve always thought that the skin of fruits contains important nutrients and fiber, and that it is the juice of the fruit which causes blood sugar spikes. What is it about the guava peel that leads to such a rapid spike in blood sugar?
3) Have other fruit peels been studied?
Does anyone know anything about fruit peels and blood sugar spikes? When my next guava-eating-mood strikes, I will peel the guava and report back with the results. Meanwhile, we can listen to Bob Marley or Sublime singing about guava jelly, which should have little to no effect on blood sugar levels. Enjoy!