Background Vitamin C insufficiency occurs across many countries and has been hypothesised to increase risk of various diseases. Few prospective studies with measured circulating vitamin C have related deficiency to disease mortality, particularly in low-income and middle-income countries.
Methods We randomly selected 948 subjects (473 males and 475 females) aged 53–84 years from a Chinese cohort and measured meta-phosphoric acid-preserved vitamin C concentrations in plasma samples collected in 1999–2000. A total of 551 deaths were accrued from sample collection through 2016, including 141 from cancer, 170 from stroke and 174 from heart diseases. Vitamin C was analysed using season-specific quartiles, as a continuous variable and as a dichotomous variable based on sufficiency status (normal >28 µmol/L vs low ≤28 µmol/L). HRs and 95% CIs were estimated using Cox proportional hazards models.
Results We found significant inverse associations between higher plasma vitamin C concentrations and total mortality in quartile (HRQ4 vs Q10.75, 95% CI 0.59 to 0.95), continuous (HRq20umol/L0.90, 95% CI 0.82 to 0.99) and dichotomous analyses (HRnormal-vs-low0.77, 95% CI 0.63 to 0.95). We observed significant lower risks of heart disease (ptrend-by-quantile=0.03) and cancer deaths (pglobal-across-quantile=0.04) for higher vitamin C, whereas the association was attenuated for stroke in adjusted models. Similar inverse associations were found when comparing normal versus low vitamin C for heart disease (HRnormal-vs-low0.62, 95% CI 0.42 to 0.89).
Conclusion In this long-term prospective Chinese cohort study, higher plasma vitamin C concentration was associated with lower total mortality, heart disease mortality and cancer mortality. Our results corroborate the importance of adequate vitamin C to human health.
- cardiovascular disease
- cohort studies
- heart disease
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Contributors S-MW contributed to study concept and design, data analysis and interpretation, and manuscript writing. J-HF contributed to data acquisition and manuscript preparation. PRT and TKL were involved in the study concept and design, data acquisition and manuscript writing. SMD contributed to data interpretation and manuscript preparation. Y-LQ and CCA were involved in the study concept and design, data acquisition, data interpretation, and manuscript preparation. All authors have seen and approved the final version of the manuscript for publication.
Funding This work was supported by the intramural funding of National Cancer Institute at the National Institutes of Health.
Competing interests None declared.
Patient consent Not required.
Ethics approval Institutional Review Board of the Cancer Hospital, Chinese Academy of Medical Sciences and the US National Cancer Institute.
Provenance and peer review Not commissioned; externally peer reviewed.