Chocolate flavanols and skin photoprotection: a parallel, double-blind, randomized clinical trial

Background: Solar ultraviolet (UV) radiation has deleterious effects on the skin, including sunburn, photoaging and cancer. Chocolate flavanols are naturally-occurring antioxidant and anti-inflammatory molecules that could play a role in preventing cutaneous UV damage. We investigated the influence of 12-week high-flavanol chocolate (HFC) consumption on skin sensitivity to UV radiation, measured by minimal erythema dose (MED). We also evaluated skin elasticity and hydration. Methods: In this 2-group, parallel, double-blind, randomized controlled trial, 74 women aged 20-65 years and Fitzpatrick skin phototypes I or II were recruited from the general community in Quebec City, for randomization to either HFC (n = 33) or low-flavanol chocolate (LFC) (n = 41). A blocked randomisation (4), considering date of entry, skin type and age as factors, generated a sequentially-numbered allocation list. Study participants and research assistants were blinded. Totally, 30 g of chocolate were consumed daily for 12 weeks, followed by a 3-week washout period. MED was assessed at baseline and at 6, 9, 12 and 15 weeks. Main outcome was changes in MED at week 12. Results: 33 participants in the HFC group and 41 in the LFC group were analyzed with 15 weeks of follow-up. Both groups showed similarly-increased MED at 12 weeks (HFC: 0.0252 +/- 0.1099 J/cm(2) [mean +/- standard deviation (SD)]; LFC: 0.0151 +/- 0.1118; mean difference (MD): 0.0100 J/cm(2); 95% confidence interval (CI): -0.0417 to 0.0618). However, after 3-week washout, the HFC group presented decreased MED (-0.0248 +/- 0.1145) whereas no effect was seen in the LFC group (0.0168 +/- 0.1698) (MD: -0.0417; 95% CI: -0.1106 to 0.0272). Net temple elasticity increased slightly but significantly by 0.09 +/- 0.12 mm in the HFC group at 12 weeks compared to 0.02 +/- 0.12 mm in the LFC group (MD: 0.06; 95% CI: 0.01 to 0.12). No significant adverse events were reported. Conclusion: Our study failed to demonstrate a statistically-significant protective effect of HFC vs. LFC consumption on skin sensitivity to UV radiation as measured by MED.