Assessment of selenium intake using data from the UK National Diet and Nutrition Survey: Methodological challenges

Concerns have been raised about the adequacy of dietary selenium (Se) intake in the UK population in recent years, but because the safe intake range is narrow, it is important to be able to measure intakes as accurately as possible.

We assessed Se exposure in UK adults by comparing reported dietary intakes from the National Diet and Nutrition Survey (NDNS) with estimated intakes from plasma Se concentrations obtained from the European Food Safety Authority (EFSA) model. For the purpose of this study, we used NDNS data on UK adult population divided in the two periods 1-11 and 12-15 years, carried out in 2008-2019 and 2019-2023. We assessed Se exposure in plasma and compared dietary intake from NDNS (Se-NDNS) with the plasma-derived EFSA estimates (Se-EFSA).

Mean plasma Se concentrations were higher in years 12-15 compared to years 1-11 (95.54 vs 81.33 µg/L). Dietary intakes in the first period were similar for both Se-NDNS and Se-EFSA (46.79 vs. 47.28 µg/day), whereas in the most recent period Se-EFSA yielded higher levels compared to Se-NDNS estimates (69.19 vs 43.47 µg/day). The relation between Se-NDNS and Se-EFSA was non-linear and differed by survey period, with greater variability and imprecision in plasma-derived estimates, particularly at higher intakes and in the most recent survey years. Associations were substantially similar between sex and age groups.

Our findings suggest a potential underestimate of Se exposure based on Se-NDNS dietary assessment, but also show methodological limitations and uncertainties in modelling Se intake from plasma concentrations. These results support the need to refine methods in order to make full use of biomarkers to assess Se exposure and draw conclusions about the adequacy of dietary reference values for Se, including the current UK ones.