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Carbohydrates and cancer: an overview of the epidemiological evidence
TJ Key and EA Spencer
Cancer Research UK Epidemiology Unit, University of Oxford, Oxford, UK
Objective: To assess the epidemiological evidence ondietary carbohydrates and the risk of developing cancer. Method: Review of published studies, concentrating on recent systematic reviews, meta-analyses and large prospective studies. Conclusions: Carbohydrates have not been intensively investigated in epidemiological studies of diet and cancer. There is a moderately large amount of data on the possible association between dietary fibre and therisk for colorectal cancer; the results of studies have varied and no firm conclusion can be drawn, but the available data suggest that high intakes of dietary fibre possibly reduce the risk for colorectal cancer. There are also limited data which suggest that high intakes of sucrose might increase the risk for colorectal cancer and that high intakes of lactose might increase the risk for ovariancancer. For other components of carbohydrates and other types of cancer, the available data are too sparse to draw even tentative conclusions. Further research is needed on the possible associations of carbohydrates with cancer risk.
European Journal of Clinical Nutrition (2007) 61 (Suppl 1), S112–S121; doi:10.1038/sj.ejcn.1602941
Keywords: carbohydrates; sugar; dietary fibre; cancer; reviewIntroduction
General The causes of cancer are incompletely understood, and cancers in different organs in the body can have different causes. Reviews have provided estimates that dietary factors may account for approximately 30% of cancers in industrialized countries and approximately 20% in developing countries, but it has proved difficult to clearly establish the effects of dietary factors oncancer risk (WHO, 2003a,b; Key et al., 2004). The WHO/FAO Expert Consultation in 2002 categorized putative nutritional risk factors according to the strength of the evidence available (WHO, 2003a). The only diet-related factors for which there is convincing evidence of an effect on cancer risk are overweight and obesity, alcohol, aflatoxin and Chinese-style salted fish; there is also evidence thatfruit and vegetables probably reduce the risk for some cancers, and that high intakes of preserved meat, saltpreserved foods and salt and very hot drinks and food probably increase the risk for some types of cancer (WHO, 2003a).
The body of evidence relating to diet and cancer risk in humans derives mostly from observational epidemiological studies conducted during the last 30 years, togetherwith a few randomized controlled trials. Most attention has been given to a small number of prominent hypotheses in relation to certain food groups, in particular meat, fruit and vegetables; certain macronutrients, especially fat and saturated fat; and some of the micronutrients. With the exception of dietary fibre, relatively little attention has been given to the possibility that consumption ofcarbohydrates may affect cancer risk, although some attention has been given to sucrose and recently several studies have investigated the possible associations of glycaemic index and glycaemic load with cancer risk.
Correspondence: Professor TJ Key, Cancer Research UK Epidemiology Unit, University of Oxford, Richard Doll Building, Roosevelt Drive, Oxford OX3 7LF, UK. E-mail: Tim.Key@ceu.ox.ac.ukApproach and methods of this overview Our aim in this overview is to summarize the current evidence and understanding of the possible role of carbohydrates in determining the risk for various cancers. This is not a systematic review of all relevant literature; rather, we have discussed previous assessments by expert panels (World Cancer Research Fund, 1997; Department of Health UK, 1998;...