I have to admit to being a bit skeptical about a company that is aiming to sell this product promoting all these benefits, but it's interesting nonetheless. I've seen this potential connection brought up in other forums before, although always with the caveat that no proper studies had been done. One of the interesting things is that c-peptide was a common "contaminant" in the older insulins, as it would be purified along with the insulin, and I've seen this used as a rant against the newer insulins. I know some people who've been diabetic for a long time and have no complications wonder whether this c-peptide they were getting when they were younger has anything to do with it.
Interestingly, I think the Joslin center in Boston is carrying out a study looking at people who have been diabetic for more than 50 years who, some of whom may have some residual insulin production, and they're looking into whether the c-peptide produced might have something to do with complication risk. 🙂