Plasma vitamin C and food choice in the third Glasgow MONICA population survey

Study objective-To determine the contribution of different foods to the estimated intakes of vitamin C among those differing in plasma vitamin C levels, and thereby inform dietary strategies for correcting possible deficiency. Design-Cross sectional random population survey. Setting-North Glasgow, Scotland, 1992. Participants-632 men and 635 women, aged 25 to 74 years, not taking vitamin supplements, who participated in the third MONICA study (population survey monitoring trends and determinants of cardiovascular disease). Measurements and main results-Dietary and sociodemographic information was collected using a food frequency and lifestyle questionnaire. Plasma vitamin C was measured in non-fasted venous blood samples and subjects categorised by cut points of 11.4 and 22.7 mu mol/l as being of low, marginal or optimal vitamin C status. Food sources of dietary vitamin C were identified for subjects in these categories. Plasma vitamin C concentrations were compared among groups classified according to intake of key foods. More men (26%) than women (14%) were in the low category for vitamin C status; as were a higher percentage of smokers and of those in the older age groups. Intake of vitamin C from potatoes and chips (fried potatoes) was uniform across categories; while the determinants of optimal versus low status were the intakes of citrus fruit, non-citrus fruit and fruit juice. Optimal status was achieved by a combined frequency of fruit, vegetables and/or fruit juice of three times a day or more except in older male smokers where a frequency greater than this was required even to reach a marginal plasma vitamin C level. Conclusion-Fruit, vegetables and/or fruit juice three or more times a day increases plasma vitamin C concentrations above the threshold for risk of deficiency.