Abstract
Background/Objectives: Frailty represents a critical aging-related condition, but evidence on how different sources of vitamin C relate to frailty risk remains limited. Thus, this study aimed to examine the relationship between frailty risk and sources of vitamin C intake (dietary, including fruit and vegetable (FV) vs. supplemental) among Korean adults. Method: We analyzed data from 9478 adults in the Korea National Health and Nutrition Examination Survey (KNHANES 2018–2019). Frailty was assessed using a modified Fried phenotype. A multivariable logistic regression model was used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) for frailty according to vitamin C intake source. Results: More than 60% of participants had inadequate FV intake. Significant associations were observed primarily in women. Increased FV intake (OR = 0.44, 95% CI = 0.264–0.731, comparing the highest intake group (fourth quartile, Q4) vs. the lowest intake group (first quartile, Q1)) for dietary vitamin C intake (OR = 0.60, 95% CI = 0.393–0.914, Q4 vs. Q1) and vitamin C intake from FV (OR = 0.54, 95% CI = 0.348–0.851, Q4 vs. Q1), was significantly associated with a lower risk of frailty. Women with inadequate FV intake had a higher risk of frailty (OR = 2.06, 95% CI = 1.34–3.16) compared to those with adequate intake, regardless of vitamin C supplement use. In contrast, vitamin C supplementation was not significantly associated with frailty risk in either men or women. Conclusion: A higher intake of FV and dietary vitamin C, but not supplemental vitamin C, was associated with a lower risk of frailty, particularly among women. These findings suggest that improving overall diet quality through increased FV consumption may be more effective for frailty prevention than relying on single-nutrient supplementation.