In contrast to the results for retinol, the results for total carotenoids, β-carotene, and vitamin C are more supportive of a reduction in lung cancer risk. Higher dietary intake of total carotenoids were consistent with a protective association in 18 observational studies119,121–122,125–126,132,135,139,143,146,150,153,155–156,161,173–175 and were not supportive in 6 studies.124,129,133,137,157,166 Circulating concentrations of total carotenoids have been linked to a reduced risk of lung cancer.163,172 Similar protective associations have also consistently been observed for a specific carotenoid, β-carotene. Data from 16 case-control and cohort studies93,118,122,125–126,129,135,137,139–140,148,154,160,176–178 of dietary β-carotene intake were compatible with associations in the protective direction. In only five studies121,124,134,138,152 have null findings been observed. Further bolstering the evidence in favor of a protective association between β-carotene and lung cancer are prospective studies in which β-carotene is assayed from blood that has been collected from a population that was initially cancer-free and was subsequently followed-up for the occurrence of lung cancer.163,166,168–169,172,179–180 The preponderance of evidence from observational studies thus has demonstrated a protective association between carotene (specifically, β-carotene) and lung cancer.