Niacinamide 5% improves aging skin (split-face RCT, 2005)

Fifty women applied 5% niacinamide to one half of the face and the identical cream without niacinamide to the other half, twice daily for 12 weeks, with the sides randomly assigned. Fine lines, dark spots, red blotchiness and yellowing all improved on the treated side, as did measured elasticity. Testing both creams on the same face is a strong design, since each person acts as her own control. The paper reports directions of change but no effect sizes, and all three authors worked for the manufacturer.