Power calculations: No data exist on the level of DNA methylation in the promoter region of IL-6 and TNF-α in normal healthy subjects. Power calculations reveal that 51 subjects in each group are required to have an 80% power to detect a true difference in the variable of interest at 5% significance level (calculations using G*Power software, version 3.1). A total of 60 subjects will be recruited into each group to take into consideration drop out rates.