Does Aging Affect Vitamin C Status Relative to Intake? Findings from NHANES 2017–2018

The aging population is growing and fueling a global increase in chronic diseases and healthcare expenditure. In this study, we examine vitamin C dose–concentration relationships based on data from the National Health and Nutrition Examination Survey (NHANES) 2017–2018 to identify a possible age-dependent change in intake vs. concentration relationship among non-supplemented individuals (n = 2828). The vitamin C intake was similar between the younger (18–36 years), middle (37–58 years) and older (59–80+ years) age groups; however, circulating vitamin C concentrations were significantly lower in the middle and older age groups (p < 0.001). For intakes above 75 mg/day, no significant difference in the intake vs. serum concentration relationship was identified between younger and older individuals. However, for intakes below 75 mg/day, we found significantly lower serum concentrations relative to intake for the older compared to younger individuals, despite smoking being more prevalent in the younger compared to older adults (p < 0.001). This effect persisted among non-smokers and was further exacerbated by smoking in older people. Collectively, the present study suggests that healthy aging in non-institutionalized individuals does not increase requirements for vitamin C. In contrast, the lower serum concentrations relative to intake observed in older individuals at intakes < 75 mg/day may suggest that older individuals are more sensitive to a low vitamin C intake, perhaps due to the increased impact of long-term smoking and increased chronic disease prevalence in older adults. This finding may have implications for future intake guidelines in countries with low RDAs and for WHO/FAO, but requires further investigation.