I became curious about this ingredient after purchasing a Crayons drink. I loved that this product proudly stated that it was HFCS-free, and was intrigued that it claimed to have something called "SugarGuard", which claims to regulate sugar intake. SugarGuard's magic is apparently mostly due to an "all-natural" ingredient called Fibersol-2. This is an ingredient already found in many Japanese products that doesn't seem to be popular yet over here.
A little search found a press-release like article, which states:
"A new soluble dietary fiber, Fibersol-2®, is available from Matsutani America Inc. The ingredient is a spray-dried powder produced by the pyrolysis and controlled enzymatic hydrolysis of cornstarch. This sourcing means it is Generally Recognized As Safe (GRAS) as maltodextrin, which is readily dispersible in water and carries no inherent flavor."
This explains how it qualifies as natural. Since it is made from corn (as is the rest of the known universe), this claim follows a well-worn path. But I have to say it doesn't sound very "natural", unless nature has started creating spray-dried powders that have been decomposed in a variety of ways.
The company website for this product is pretty much the opposite of delicious-sounding, including features like "Low Viscosity" and "Bland Taste". Fibersol-2's health claims come from the fact that it is "digestive-resistant". This sounds similar to the types of claims of products like Alli, and in fact Fibersol-2 was likely made in part for diet products. From the diagrams, it would appear that the fiber basically preps your digestive tract which will, in turn, apparently "increase fecal volume" and will moderate glucose levels. An unpublished study seems to suggest that this product also helps out by aiding in mineral absorption.
On the face of things, this sounds like it is probably relatively harmless, other than the fact that it promotes some bad habits (enjoying more sugar-y foods and not feeling the effects vs. learning to like things with a little less sugar) and might even have some good side-effects, probably mostly due to the fiber.
The main reason I wouldn't recommend it is that it seems like yet another part of the Giant Corn Complex, and we aren't going to get anywhere with that if we just replace HFCS with some other corn product.