Challenges in nutrition-related DNA methylation studies.

Abstract The rapid progress in nutritional epigenetics allowed for a much better understanding of the mechanisms involved in gene-nutrient interactions and the roles that nutrition has in transgenerational inheritance of acquired epigenetic traits. Studies indicated that a considerable number of nutrients or diet types are capable of inducing epimutations. In parallel, the rapid development of genome-wide DNA methylation detection methods allowed for a broader image on how nutrition impacts the epigenetic status in human and animal models. But this increased complexity in the epigenetic field and also brought important challenges that need resolution, or it suggests that some of the initial epigenetic paradigms have to be revisited or reconsidered. The aim of this review is to discuss the inherent challenges that need to be resolved, from both practical and theoretical aspects, stemming from the rapid progress in the field of nutritional epigenetics, with a focus on DNA methylation. Because such challenges are present at every stage of study development, the review systematically discusses the most common issues relevant to DNA methylation in a nutritional context. Various types of challenges and potential bias generators are discussed within study design, sample quality, detection methods, data processing, and statistical and bioinformatic analysis. Additional aspects to be considered include epigenetic heterogeneity of treatment groups, the role of genomic variability in introducing measurement bias and errors in interpretation of changes, and issues related to the final interpretation of results and in assigning functional significance. It is also posited that all these issues will be largely resolved within the next decade.