Interrelation of vitamin C, infection, haemostatic factors, and cardiovascular disease

Objective : To examine the hypothesis that the increase in fibrinogen concentration and respiratory infections in winter is related to seasonal variations in vitamin C status (assessed with serum ascorbate concentration). Design : Longitudinal study of individuals seen at intervals of two months over one year. Setting : Cambridge. Subjects : 96 men and women aged 65-74 years living in their own homes. Main outcome measures : Haemostatic factors fibrinogen and factor VIIC; acute phase proteins; respiratory symptoms; respiratory function. Results : Mean dietary intake of vitamin C varied from about 65 mg/24 h in winter to 90 mg/24 h in summer; mean serum ascorbate concentration ranged from 50 μmol/l in winter to 60 μmol/l in summer. Serum ascorbate concentration was strongly inversely related to haemostatic factors fibrinogen and factor VIIC as well as to acute phase proteins but not to self reported respiratory symptoms or neutrophil count. Serum ascorbate concentration was also related positively to forced expiratory volume in one second. An increase in dietary vitamin C of 60 mg daily (about one orange) was associated with a decrease in fibrinogen concentrations of 0.15 g/l, equivalent (according to prospective studies) to a decline of approximately 10% in risk of ischaemic heart disease. Conclusion : High intake of vitamin C has been suggested as being protective both for respiratory infection and for cardiovascular disease. These findings support the hypothesis that vitamin C may protect against cardiovascular disease through an effect on haemostatic factors at least partly through the response to infection; this may have implications both for our understanding of the pathogenetic mechanisms in respiratory and cardiovascular disease and for the prevention of such conditions. Key messages Key messages A winter increase in fibrinogen concentration has been associated with a winter increase in respiratory infection Vitamin C status is related to fibrinogen and factor VIIC concentrations as well as markers of infections including acute phase proteins and to respiratory function Maintaining adequate vitamin C intake—for example, by eating an extra orange daily—may reduce some of the seasonal variation in mortality Differences in vitamin C status, infection, and fibrinogen concentration might explain some of the observed socioeconomic differential in respiratory and cardiovascular disease