Since water kefir grains grow in the presence of sucrose, it may be a concern for diabetics. The following information may put you at ease. First, a little background on the sugar composition. Table sugar is typically used to grow the grains because it requires the breakdown of the sugar molecules to glucose and fructose. The grains use the glucose to grow and multiply.
More than 80% of the sugar in the growth medium is consumed by the water grains. What is left in the final beverage is mostly fructose, some of which is converted to a myriad of compounds, most of which can be classified as health-promoting. So what is left is in fact a form of honey, for honey is mostly fructose.
I've done some serious calculations and I've concluded that it contains <4 g of sugar per cup of water kefir. This is what I did:
1. First ferment: Used 1 Tbsp br sugar (13.8 g) in 1 cup (C)of spring water.
2. Second ferment: Use fruit juice with sugar content of 35 g/1 C. Used 1 cup fruit juice to 6 cups of kefir from the 1st ferment, 35g/7 C = 5g/ C.
3. Total sugar used in 1 C of water kefir = 13.8 g + 5 g = 18.8 g
4. Assuming >80% of sugar is digested away by the grains per Dom's site, leaving <20% left; 18.8g x .2 = 3.76 g => less than 4g of sugar left in the water kefir per cup.
The calculation may differ depends on the type of sugar you use, how much other additives you include, such as blackstrap molasses, and the length of the fermentation. But this is a pretty decent estimate.
So if you substitute your fruit juice intake with water kefir, not only can you easily reduce your sugar intake by a huge margin, you will also reap a huge benefit from the probiotics in the kefir.
Best to your health!
For more specifics and photo image of how much sugar is left, please see source below.