Oral NMN is unlikely to be absorbed intact because it has a charged phosphate group and is subject to hydrolysis by non-specific phosphatases in the small intestine.

“oral nmn I would bet money that it's not absorbed intact and that's because nmn has a charged phosphate group on it and generally charged phosphates cannot cross cells and so their hydrolyzed and even if it were to be true that there were transporters and the intestines I could take nmn up intact it probably still would not be absorbed intact because the phosphatase is in the small intestine that cleaved the phosphates off of everything that all the molecules in the food you eat do so non-specifically to all of the molecules in the food you eat”