I was asked the other day what the GI of Trehalose was. They had been looking around on the internet and become confused because some sites say it has a GI of 70 while others just suggest that it is low - some suggest it is around 30.

So here is the truth.  In order to measure anything you need to have a standard to measure against. The common standard that foods are tested against for GI is the WHO/FAO protocol.

This protocol includes the following:

• Each subject is studied 5 times per product.
• The test food/beverage has to be investigated twice and the reference food has to be investigated three times. It has been shown that it is necessary to repeat the reference food greater than twice to reduce the variation of the mean GI value since the reference data is used to calculate the test food/beverages GI.
• Subjects are studied for 2h each time with seven finger prick samples.
• Glucose analysis is carried out on the approved glucose analyser. Three reference values are run per set of three subjects to ensure no drift in results.

Now the important thing to note is that the 7 blood samples are taken over a 2 hour period (normally every 15 minutes).  We know that Trehalose isn't broken down until it gets to the area in the small intestine where Trehalase, an enzyme, is present. The time it takes for the Trehalose to get to this area is almost invariably more than 2 hours, probably 4 hours is more likely, so that there is no effect on blood glucose levels during the 2 hour testing phase.  If we continued testing until the Trehalose reached the enzyme and is digested then we would notice a small rise in blood glucose levels. The reason its small is that the trehalose has been distributed along the entire gut and some has been absorbed as Trehalose.

So the truthful answer is that the current approved GI testing protocols are unsuitable for measuring the effect of Trehalose.