Oligosaccharides occur naturally in human milk moreso than in cows'. They are, basically, a sugar molecule that is easier to digest. They also aid in colon health, along the lines of [i:9fc3f13f9d]acidophilus[/i:9fc3f13f9d] found in yogurt.
This is a complete guess on my part, but I assume, since Asian people tend to be more lactose-intolerant and do not consume as much dairy as Westerners, the supplementation of small amounts of oligosaccharides to liquid milk is an attempt to make the beverage more easily digestible to dairy-wary China. The supplemented sugars can be fructose-derived (instead of galactose-based), and I would guess it is fruit sugars that are added for purposes of compatibility.
The macronutrient breakdown of your favorite brand falls roughly within Zone ratios, and since you report no sensitivity to the minor change in its formula, I would say it would make a fine Zone snack.
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