The Nadir Range of the U-Shaped Curve

Vitamins, micronutrients and electrolytes are essential components of optimal cell function. Reliable optimal range of their serum concentrations should be set according to the lowest relative risk (RR) of morbidity and mortality. Optimal concentrations and adjustment to nadir ranges might minimize the RRs of a long list of both non-communicable diseases (NCDs or chronic diseases) as well as communicable diseases, and consequently affect life expectancy and decrease disability. Efforts should be made to define optimal serum concentrations of these essential nutrients. The present dietary recommended intakes (DRIs) for the micronutrients are mostly based on data extracted from a “healthy population”, and “normal” values are defined as a mean ±2 SD and not by the lowest morbidity/mortality. Definition according to the nadir ranges of serum concentrations of these nutrients, however, might better predict nutrient requirements than the outdated DRI methodology. Most metabolites have a narrow reliable nadir range for their optimal activity. The concept of the optimal nadir ranges is well demonstrated by examples of U-shaped curves presented here. Thus, optimal nutrient concentrations should be redefined by further studies, based on comprehensive data.