Plasma vitamin C concentrations and risk of incident respiratory diseases and mortality in the European Prospective Investigation into Cancer-Norfolk population-based cohort study.
Level 3 - non-randomized controlled study
Prospective observational cohort study
PubMed 30705384 · doi:10.1038/s41430-019-0393-1
What was done
A prospective cohort of 19,357 men and women aged 40-79 years without baseline respiratory disease from the EPIC-Norfolk study (UK) was followed from 1993-1997 through March 2015 (>300,000 person-years). Cox proportional hazards models estimated hazard ratios (HR) for incident respiratory diseases and mortality across quartiles of baseline plasma vitamin C concentrations, adjusting for potential confounders.
What was found
During follow-up, 3,914 incident non-cancer respiratory events, 407 non-cancer respiratory deaths, 367 incident lung cancers, and 280 lung cancer deaths occurred. Comparing the top to bottom quartile of plasma vitamin C, incident lung cancer HR was 0.57 (95% CI: 0.41-0.81) and mortality HR was 0.54 (95% CI: 0.35-0.81). For any non-cancerous respiratory disease, incident HR was 0.85 (95% CI: 0.77-0.95) and mortality HR was 0.81 (95% CI: 0.59-1.12). Incident chronic respiratory disease HR was 0.81 (95% CI: 0.69-0.96; mortality HR 0.85, 0.44-1.66) and pneumonia HR was 0.70 (95% CI: 0.59-0.83; mortality HR 0.61, 0.37-1.01). In non-smokers, lung cancer incidence and mortality risk reductions were 42% and 53%, respectively.
Why it matters
The findings demonstrate that higher circulating vitamin C, serving as a biomarker of fruit and vegetable intake, is prospectively linked to reduced incidence and mortality across multiple respiratory conditions, independent of smoking status.
Limits
The study is observational and cannot establish causality. Vitamin C was measured once at baseline and may not capture dietary changes over the ~20-year follow-up. Plasma vitamin C may reflect overall healthy lifestyle or diet quality, introducing potential residual confounding. The sample was restricted to adults aged 40-79 from a single UK region.
Cited by
- supports In a prospective study of over 19,000 people followed for 16.5 years, those with the highest blood vitamin C concentrations were 15% less likely to develop respiratory conditions and 46% less likely to die of lung cancer compared to those with the lowest levels.