It's PNAS. The open secret about PNAS is that they often publish pure shit, since members of the academy get freebies all the time. They once published a study that claimed that moths and caterpillars evolved separately then merged into a single organism. Whether they can make chocolate with less fat is a totally separate issue from whether it's "healthier" or "tastes better." Not sure how they got away with those kind of qualitative claims, except that, well, it's PNAS.