Dietary Vitamin C Intake and Lung Function in Rural China

Abstract

The relation between dietary vitamin C intake and pulmonary function was investigated in a cross-sectional study carried out in 69 counties in rural China in 1989. Within each of the 69 counties, 120 subjects aged 35-64 years were identified using a three-stage random clustering procedure. Each subject underwent pulmonary function testing, completed a detailed questionnaire, and provided a blood sample. Dietary vitamin C intakes were estimated among half of the subjects using a 3-day weighed record of household food intake. Plasma vitamin C was measured in sex-specific blood pools created from individual samples in each geographic area. Among the 3,085 subjects for whom there were complete data, dietary intake of vitamin C (151 mg/day (standard deviation, 111)) was significantly related to forced expiratory volume in the first second (FEV1) and forced vital capacity after adjustment for sex, age, height, weight, total caloric intake, tobacco smoking, and education. An increase of 100 mg/day in vitamin C intake was associated with an increase of 21.6 ml (95% confidence interval -0.4 to 43.5) in FEV1 and an increase of 24.9 ml (95% confidence interval 0.2 to 49.6) in forced vital capacity. No significant interaction with smoking status was observed. A significant positive association was also observed at the geographic level, between county-pooled plasma vitamin C and mean FEV1. These data support the hypothesis that dietary vitamin C may protect against the loss of pulmonary function.

Diet and 20-year chronic obstructive pulmonary disease mortality in middle-aged men from three European countries

“…If heavy smokers tend to under-report the number of cigarettes they usually smoke, which is not unlikely, this would even cause dilution of observed dietary effects. Possibly even more important is the fact that in the majority of epidemiological studies on diet and COPD, that reported on whether observed effects varied by smoking status (smoker vs non-smokers, current vs former vs never smokers or interaction with smoking status), such variation was not observed (Strachan et al, 1991;Schwartz & Weiss, 1994;Dow et al, 1996;Chuwers et al, 1997;Hu et al, 1998;Butland et al, 2000). It is therefore unlikely that the observed associations in our study are substantially biased by residual confounding by smoking.…”

Allergic sensitization and diet: ecological analysis in selected European cities

“…A large cross-sectional study conducted in China found that forced expiratory volume in one second (FEV1) increased by 21.6 mL (95% CI -0.4 -43.5) and forced vital capacity (FVC) by 24.9 mL (95% CI 0.2 -49.6) for every 100 mg . day -1 increase in intake of vitamin C [31]. A cross-sectional study of 6,555 Dutch adults found a higher FEV1 and FVC in subjects with a high intake of vitamin C(w90th percentile) compared to subjects with low intake (vl0th percentile) [32].…”

The relationship of dietary patterns with adult lung function and COPD

“…Observational studies have reported beneficial effects of a higher intake of fruit on adult lung function [36][37][38][39][40], incident COPD risk [41] and COPD mortality [42], and of a higher intake of whole grains on lung function [36] and lower mortality from chronic respiratory disease [43]. Many studies have found a positive association between vitamin C intake and adult lung function [44][45][46][47][48][49] and there is some evidence in support of flavonoids [50]. The lack of benefit of vitamin supplementation on lung function and hospital admissions for COPD [8] may indicate that observational associations with vitamin C intake were confounded [51], either by other nutrients or by non-dietary lifestyle factors.…”