title: Epidemiological and clinical studies of nutrition.
abstract: In this review, we briefly summarize some of the key developments in nutritional epidemiology and cancer over the past two decades with a focus on the strengths and limitations of study designs and dietary assessment methods. We present the evidence on dietary fat, meat, fiber, antioxidant nutrients, and calcium in relation to carcinogenesis from large cohort studies and randomized clinical trials (RCTs) and refer to the conclusions of the 2007 World Cancer Research Fund/American Institute for Cancer Research summary report. One prominent theme that emerged is the lack of concordance of results from RCTs and observational studies. There are multiple potential reasons for these discrepancies, including differences in study population, dose and timing of the exposure, adherence to an intervention, length of follow-up, and the primary endpoint. Therefore, null findings of RCTs do not necessarily indicate a lack of effect for the tested dietary factors on cancer risk, as some of these nutrients may have chemopreventive effects if given at the right time and in the right dose. It is likely that potential benefits from diet are due to a combination of food constituents rather than single components acting in isolation. Future efforts need to recognize the integrative nature of dietary exposures and attempt to study nutrients in the larger context of the foods and diets in which they are consumed.
authors: Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Rockville, MD 20852, USA. gibsontm@mail.nih.gov
authors: Todd M
authors: TM
authors: Gibson
authors: Leah M
authors: LM
authors: Ferrucci
authors: Joseph A
authors: JA
authors: Tangrea
authors: Arthur
authors: A
authors: Schatzkin
mesh_terms: D000975:Antioxidants / Q000008:administration & dosage; D002136:Calcium, Dietary / Q000008:administration & dosage; D004032:Diet / Q000009:adverse effects; D004041:Dietary Fats / Q000009:adverse effects; D004043:Dietary Fiber / Q000008:administration & dosage; D055951:Functional Food; D008460:Meat / Q000009:adverse effects; D009369:Neoplasms / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control*
chemical_list: D000975:Antioxidants; D002136:Calcium, Dietary; D004041:Dietary Fats; D004043:Dietary Fiber