Can diet really change telomere length?
Crous-Bou et al  present a compelling argument that consumption of a Mediterranean diet may delay ageing based on cross-sectional analysis of dietary intake and telomere length in a large cohort of women. They suggested that a three point change in the Alternative Mediterranean Diet score would correspond on average to 4.5 years of ageing based on telomere length. Whether the Mediterranean Diet score is actually associated with longitudinal changes in telomere length is debatable given the individual heterogeneity in age-related telomere changes [2,3]. If consuming a Mediterranean diet does truly change telomere length, it raises the question how many weeks, months or years would one need to consume a Mediterranean diet for it to alter telomere length?
We need to be careful about interpreting studies on potential anti-ageing factors that use telomere length as a measure of ageing. Telomere length is often used as a biomarker of ageing in cross-sectional cohort studies, based on the principle that telomeres are shortened during each cell division cycle [4,5]. However, the reverse is also true that telomeres can be restored or even elongated by the enzyme telomerase reverse transcriptase each cell division cycle. In addition, the gene expression of telomerase reverse transcriptases vary depending on cell types, and is much higher in rapidly proliferating cells. For example in embryonic stem cells telomere length is maintained despite numerous cell divisions. Furthermore, in the first 3 years of life, telomere shortening in infants is more than fourfold higher than adults .
An assumption inherent in the use of telomere length or telomerase reverse transcriptase activity as biomarkers of ageing, is that they change linearly with biological age. However, evidence of telomere length changes in longitudinal adult cohorts suggests that telomere length is not a robust biomarker of ageing [2,3]. For example, a longitudinal study of telomeres in leukocytes of adults with stable coronary artery disease reported that telomere length can both increase or decrease over five years . While telomere length was on average decreased by 42 base pairs per year, notably 23% of individuals showed telomere lengthening, 45% of individuals showed telomere shortening and 32% of individuals showed no change in telomere length . The most significant predictor of telomere shortening was baseline telomere length, which implies that longer telomeres are more likely to show shortening over five years compared to shorter length telomeres. These findings imply that telomere length is a poor biomarker of ageing in humans and we really need to identify a more robust biomarker of ageing which changes consistently within individuals over time and that can be measured in large population cohorts.
1 Crous-Bou M, Fung TT, Prescott J, et al. Mediterranean diet and telomere length in Nurses’ Health Study: population based cohort study. BMJ 2014;349:g6674.
2 Farzaneh-Far R, Lin J, Epel E, et al. Telomere length trajectory and its determinants in persons with coronary artery disease: longitudinal findings from the heart and soul study. PloS One 2010;5:e8612. doi:10.1371/journal.pone.0008612
3 Nordfjäll K, Svenson U, Norrback K-F, et al. The individual blood cell telomere attrition rate is telomere length dependent. PLoS Genet 2009;5:e1000375. doi:10.1371/journal.pgen.1000375
4 Gardner M, Bann D, Wiley L, et al. Gender and telomere length: systematic review and meta-analysis. Exp Gerontol 2014;51:15–27. doi:10.1016/j.exger.2013.12.004
5 Haycock PC, Heydon EE, Kaptoge S, et al. Leucocyte telomere length and risk of cardiovascular disease: systematic review and meta-analysis. BMJ 2014;349:g4227.
6 Zeichner SL, Palumbo P, Feng Y, et al. Rapid telomere shortening in children. Blood 1999;93:2824–30.
Competing interests: No competing interests