No they don't reduce it

But Guava Leaf Tea works like Apple Cider Vinegar on the digestive system

If you take/drink either one "before a meal" they will slow down your digestion for the next couple of hours.

So all the sugars/starches in your meal will still get turned into blood sugar, just over a little bit longer period of time

If that is 40 carbs worth all 40 will still get in your blood, just slower so your system has a bit longer to react

So does it "slow down digestion" - Yes

Does it lower blood sugar - NO

Does it spread it out over a longer period of time without spiking as high - Yes