12.Cho S, Lee DH, Won CH, Kim SM, Lee S, Lee MJ, Chung JH. Differential effects of low-dose and high-dose beta-carotene supplementation on the signs of photoaging and type I procollagen gene expression in human skin in vivo. Dermatology. 2010;221(2):160-71. http://www.ncbi.nlm.nih.gov/pubmed/20516658
13.Jeon YJ, Myung SK, Lee EH, et al. Effects of beta-carotene supplements on cancer prevention: meta-analysis of randomized controlled trials. Nutr Cancer. 2011 Nov;63(8):1196-207. http://www.ncbi.nlm.nih.gov/pubmed/21981610
14.Karppi J, Kurl S, Mäkikallio TH, Ronkainen K, Laukkanen JA. Low levels of plasma carotenoids are associated with an increased risk of atrial fibrillation. Eur J Epidemiol. 2013 Jan;28(1):45-53. http://www.ncbi.nlm.nih.gov/pubmed/23238698