With the rising prevalence of obesity globally, increasing proportions of the population may not be covered by current recommended daily allowances (RDAs) that are supposed to provide 97.5% of the population with a sufficient nutrient status but are typically based on a healthy young 70 kg male reference person. Using the EPIC-Norfolk (UK) and the NHANES (US) cohorts, we estimated the effect of body weight on the dose-concentration relationship to derive weight-based requirements to achieve an 'adequate' plasma concentration of vitamin C estimated to be 50 µmol/L. Inverse correlations between body weight and vitamin C were observed in both cohorts ( p  < 0.0001). Moreover, only about 2/3 of the cohorts achieved an adequate plasma vitamin C status by consuming the RDA or above, while only 1/3 to 1/2 of the cohorts achieved adequacy by an intake of the local RDA ± 10%. Using vitamin C as an example, the present data demonstrate that a considerable and expectedly increasing proportion of the world population is unable to achieve an adequate target plasma concentration with the current recommended daily intakes of vitamin C. This needs to be considered in future public health recommendations.