The effect of ascorbic acid on plasma lipids and oxidisability of LDL in male smokers
Objective: The aims of this study were to investigate the effect of ascorbic acid (AA) supplementation on the oxidisability of low density lipoprotein (LDL) in vitro and on plasma lipoproteins under controlled dietary conditions. Design: Randomised single-blind cross-over trial. Setting: Free living subjects. Subjects: Eight male smokers (age: 25±2.4 y, BMI: 20.7±0.5, cigarettes per day: 19.1±2.4; means±s.e.). Interventions: Dietary intake was determined and all subjects were advised to achieve an intake as close as possible to the recommended dietary intake of AA (40 mg). After two weeks on the baseline diet, subjects were asked to consume 1 g AA per day for two weeks followed by two weeks of placebo supplementation, or vice versa. In view of the carry-over effects of plasma AA, a wash-out period was incorporated between treatments. Duplicate venous blood samples were collected before and after supplementation and the plasma concentrations of AA, lipids and lipoproteins were determined. The in vitro copper-induced oxidisability of LDL was assessed by monitoring of the absorbance of 234 nm. Results: No changes in the plasma lipids or the oxidisability of LDL were found after AA supplementation compared to placebo. Plasma AA concentrations doubled on average after supplementation indicating that the lack of effect was not a result of poor compliance. Conclusions: AA supplementation at this dose did not alter plasma lipids of LDL oxidisability in male smokers. Sponsorship: University of Sydney.