475 women and 473 men aged 53 to 84 years old, who were enrolled in the NIT cohort in Linxian, China were involved in the study, who had plasma samples collected that were analyzed for vitamin C levels.
In total 551 deaths occurred: 174 caused by heart disease, 170 from stroke, 141 resulting from cancer, and 66 due to other causes during the 16.4 year follow up period. Among subjects with plasma vitamin C concentrations among the top 25% the adjusted risk for dying from any cause was 25% lower than that of those in the lowest quarter. Those within the highest 25% of plasma vitamin C levels had a 28% lower adjusted risk of dying from stroke or cancer, and 35% lower risk of dying from heart disease than that of those in the lowest quarter.
When participants with low vitamin C levels and normal vitamin C levels were compared, normal levels were associated with a 23% lower risk of premature mortality and a 38% lower risk of dying from heart disease than those in the lowest quarter. Low vitamin C was defined as 28 micromoles per liter or below; and normal levels were defined as greater than 28 micromoles per liter.
Oxidative stress promotes endothelial dysfunction that underlies heart disease by increasing inflammation and lipid peroxidation as well as decreasing nitric oxide availability, and was noted to be lowered by vitamin C. DNA damage associated with cancer is also promoted by oxidative stress.
According to the researchers this is the first known study to find general benefits for higher plasma vitamin C concentrations on total and cause specific mortality, including heart diseases and cancer in a long term prospective cohort in China. Levels of higher plasma vitamin C concentration was associated by the researchers with lower total mortality, heart disease mortality, and cancer mortality with results corroborating the importance of adequate vitamin C to human health.
