Recommended summer sunlight exposure levels can produce sufficient (>or=20 ng ml(-1)) but not the proposed optimal (>or=32 ng ml(-1)) 25(OH)D levels at UK latitudes - Rhodes, L E; Webb, A R; Fraser, H I; Kift, R; Durkin, M T; Allan, D; O'Brien, S J; Vail, A; Berry, J L (J Invest Dermatol, 2010)