Can nutritional biomarkers help to provide the ‘missing link’ in diet–diabetes associations?

Abstract

93 ISSN 1758-1907 10.2217/DMT.12.83 © 2013 Future Medicine Ltd Diabetes Manage. (2013) 3(2), 93–96 There are two well-known facts regarding diabetes prevention. First, the prevention of diabetes is important, nay urgent, given its increasing burden, with an estimated 366 million individuals worldwide with diabetes in 2011, projected to rise to 552 million by 2030 [1], and it is a leading cause of death [2]. Second, there is evidence from randomized trials that the primary prevention, or at least the delay of onset, of Type 2 diabetes is possible with lifestyle interventions, including diet [3]. What is not well known, however, is which specific dietary factors relate to diabetes risk in what specific ways, and what dietary advice is optimal for populations and individuals for the prevention of diabetes. This is despite the fact that the potential contribution of dietary intake to the prevention of chronic diseases, including diabetes, has been prominently highlighted by many international and national agencies such as WHO [4]. In reality, the scientific literature and the media are full of examples of inconsistent and contradictory reports of associations between dietary factors and the risk of diabetes, or indeed other medical conditions, often leaving the readers confused. Let us consider one example. It has been reported that eating one or more portions per week of fish versus less than one portion per week was associated with a 25% lower risk of incident Type 2 diabetes among men and women in the EPIC Norfolk study, which included approximately 22,000 participants (odds ratio: 0.75; 95% CI: 0.58–0.96) [5]. In the same year (2009), there were reports from the USA [6] and The Netherlands [7] that fish intake is associated with an increased risk of diabetes, and in the US study an increased risk of diabetes was also associated with greater dietary long-chain fatty acid intake, derived from the food frequency questionnaire [6]. Not surprisingly, the public are confused: should they or should they not eat fish? The exact reasons for the lack of consensus regarding the associations for fish intake observed between the different studies are unclear, but it has been discussed in a systematic review that they could include geographical or cultural differences, including different cooking methods or levels of contamination of fish, such as by persistent organic pollutants or mercury [8]. What is not known, however, is to what extent these different findings are a result of measurement error introduced by the self-report methods that are currently available to researchers to assess dietary intake. While a validated food frequency questionnaire was