Effect of gender, age, diet and smoking status on the circadian rhythm of ascorbic acid (vitamin C) of healthy Indians

Background/Objectives: To determine effects of gender, age, diet, and smoking status on circadian rhythm characteristics of ascorbic acid (vitamin C). Subjects/Methods: Ascorbic acid was measured spectrophotometrically in serum collected from 162 healthy volunteers (103 males and 59 females; 7–75 years) every 6 h for 24 h (4 samples). Data were analyzed by single and population mean cosinor. Effects of gender, age, diet (vegetarian vs. omnivore), and smoking status on the rhythm-adjusted mean (MESOR) and circadian amplitude were examined by multiple analysis of variance. Results: A circadian rhythm is documented with statistical significance by population mean cosinor. In addition to effects of gender and age, the MESOR is affected by diet and smoking status. The circadian amplitude changes nonlinearly as a function of age. The circadian acrophase advances with increasing age. Conclusion: The present observations confirm a definite circadian rhythm in ascorbic acid concentrations with significant effects of age, diet and smoking status in clinical health. Mapping the circadian rhythm of serum ascorbic acid in health can help explore its role in different pathophysiological conditions as pre-disease conditions may be characterized by alterations in the circadian amplitude and/or phase before there is a change in mean value.