title: Influence of observational study design on the interpretation of cancer risk reduction by carotenoids.
abstract: Recently published literature has been reviewed to determine whether lycopene, beta-carotene, alpha-carotene, and beta-cryptoxanthin are associated with reductions in cancer risk and whether study findings differ by study design. A total of 57 publications meeting pre-defined inclusion and exclusion criteria were identified, with the majority (55) being observational studies. None of the intervention studies supported a significant reduction in cancer risk with carotenoid (beta-carotene) supplementation. The majority of observational studies did not support significant reductions in cancer risk with increased carotenoid dietary intakes/circulating levels. A larger percentage of case-control studies supported significant associations between increased dietary intakes/circulating levels of carotenoids relative to prospective (cohort and nested case-control) studies. Compared to prospective studies, case-control studies cannot be used to establish temporality and may be more susceptible to selection and recall biases. Thus, diet-disease relationships suggested by case-control studies should ideally be confirmed by additional evidence from prospective studies.
authors.affiliation: Cantox Health Sciences International, Mississauga, Ontario, Canada. kmusa-veloso@cantox.com
authors.forename: Kathy
authors.initials: K
authors.lastname: Musa-Veloso
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Card
authors.forename: Andrea W
authors.initials: AW
authors.lastname: Wong
authors.forename: Dale A
authors.initials: DA
authors.lastname: Cooper
mesh_terms: D016588:Anticarcinogenic Agents; D002338:Carotenoids / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology; D004032:Diet; D006801:Humans; D009369:Neoplasms / Q000517:prevention & control*; D012107:Research Design; D012307:Risk Factors; D040242:Risk Reduction Behavior
chemical_list: D016588:Anticarcinogenic Agents; D002338:Carotenoids