Researchers at Yunnan University applied topical nicotinamide (NAM, the amide form of vitamin B3, also called niacinamide) to UV-irradiated mouse skin and found it reversed most of the visible and structural hallmarks of photoaging. Working backward from public human and mouse datasets showing that NAD+ synthesis collapses in aged skin, the team treated photoaged mice with four concentrations of NAM cream. The treatment thinned the thickened, sun-damaged epidermis, restored collagen and skin-barrier proteins, lowered DNA-damage and senescence markers (gamma-H2AX, p53, p21), and quieted the inflammatory secretome (SASP) that senescent cells pump out. The effect on skin structure was large, but the paper stops short of proving the NAD+ mechanism it proposes, and a commercial cosmetics interest sits in the author list.
Sunlight ages skin, and the biology behind that is now well mapped: ultraviolet radiation shreds DNA, generates reactive oxygen species, pushes skin cells into a zombie-like senescent state, and triggers those cells to leak a toxic broth of enzymes and inflammatory signals that dissolve collagen and wreck the skin barrier. This study asks a narrower question that biohackers and dermatologists both care about: can nicotinamide, one of the cheapest and best-tolerated skincare ingredients on the market, interrupt that cascade in living skin rather than just in a dish?
The team first built its case from existing data. Mining public gene-expression datasets from photoaged mice and single-cell data from human skin donors of different ages, they showed that the machinery cells use to make NAD+, the central energy and repair molecule, is consistently switched down in aged and sun-damaged skin. A separate human metabolomics dataset confirmed that nicotinamide itself is depleted in the skin of older women. The logic follows: if aging drains NAD+ and its precursor, then topping up the precursor might help.
To test that in vivo, they irradiated the backs of female mice for nine weeks with a solar simulator, then applied nicotinamide cream at four strengths for the final seven weeks. The results were visually and structurally clear. Untreated UV skin thickened dramatically, a classic photoaging response, ballooning from roughly 18 micrometers to 81 micrometers. Nicotinamide brought that back down toward 27 to 36 micrometers, reversing the bulk of the damage. It restored collagen I and the barrier proteins ZO1 and E-cadherin, and it cut the senescence markers p53 and p21 along with the collagen-destroying enzymes MMP1 and MMP12.
The bigger idea is mechanistic elegance rather than a new drug. Nicotinamide appears to work on two fronts at once: it slows cells from becoming senescent in the first place (by supporting DNA repair and blocking the p53-p21 arrest switch), and it muzzles the inflammatory SASP output of the cells that do senesce. The authors also flag a wrinkle worth remembering. The best structural results came at intermediate 2 to 5 percent doses, not the highest 12.5 percent, suggesting benefit plateaus and more is not better.
Actionable Insights
The practical, human-relevant signal here is for topical niacinamide, not oral supplements, and this paper actually undercuts the oral NAD+ story. The take-home is that topical nicotinamide in the 2 to 5 percent range plausibly protects and partly repairs sun-damaged skin, which aligns with a large existing cosmetic literature.
On effect size, the standout number is epidermal thickness. UV irradiation drove a roughly 4.6-fold increase in epidermal thickness (17.7 to 81.4 micrometers). At 2 percent nicotinamide, thickness fell to 26.5 micrometers, reversing about 86 percent of the UV-induced thickening. At 5 percent, about 84 percent was reversed. The standardized effect size (Cohen’s d) for treated-versus-untreated skin exceeds 11, which is enormous, though inflated by unusually tight standard deviations and tiny samples. Notably, the highest dose (12.5 percent) reversed only about 72 percent, less than the low dose, so the benefit peaks around 2 to 5 percent and then declines.
The critical caveat for supplement users: the authors themselves cite recent human data showing oral nicotinamide did not meaningfully raise blood NAD+, whereas NR and NMN nearly doubled it. So the message is topical B3 on skin, not a reason to swallow more niacinamide for systemic anti-aging.
Context and Source
- Open Access Paper: Nicotinamide Improves Skin Photoaging in Mice by Delaying Cellular Senescence and Suppressing the Senescence-Associated Secretory Phenotype.
- Institution and country: Yunnan University (State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan) and the Yunnan Characteristic Plant Extraction Laboratory, Kunming, China.
- Journal and impact evaluation: Current Issues in Molecular Biology (CIMB), published by MDPI. The 2024 Journal Impact Factor is 3.0 (Clarivate JCR, released 2025); the journal’s CiteScore sits near 3.7 and it holds a Q2 quartile ranking. The impact score of this journal is 3.0, evaluated against a typical high-end range of 0 to 60+ for top general science, therefore this is a Low-to-Medium impact journal.