September 25, 2018

A study reported on August 12, 2018 in the Journal of Epidemiology and Community Health has uncovered an association between higher plasma vitamin C levels and a lower risk of mortality during more than 16 years of follow-up.

The study included 473 men and 475 women between the ages of 53 and 84 who were enrolled in the General Population Nutrition Intervention Trial (NIT) cohort in Linxian, China. Plasma samples collected from 1999 to 2000 were analyzed for vitamin C levels.

During the 16.4-year follow-up period, 551 deaths occurred: 170 from stroke, 174 caused by heart disease, 141 resulting from cancer, and 66 due to other causes. Among subjects whose plasma vitamin C concentrations were among the top 25%, the adjusted risk of dying from any cause during follow-up was 25% lower than the risk experienced by subjects whose vitamin C levels were among the lowest quarter. Those whose plasma vitamin C levels were among the highest 25% had an adjusted risk of dying from cancer or stroke that was 28% lower and a risk of dying from heart disease that was 35% lower than subjects whose levels were lowest.

When subjects with low vitamin C levels (defined as 28 micromoles per liter or below) and normal levels (greater than 28 micromoles per liter) were compared, a normal level was associated with a 23% lower risk of premature mortality and a 38% lower risk of dying from heart disease, in comparison with low levels.

As a possible reason for their findings, Shao-Ming Wang and colleagues note that oxidative stress is lowered by vitamin C. Oxidative stress can promote endothelial dysfunction that underlies heart disease by increasing inflammation and lipid peroxidation and decreasing nitric oxide availability. Oxidative stress also causes DNA damage associated with cancer.

"This study is the first to find the general benefits for higher plasma vitamin C concentrations on total and cause-specific mortalities, including cancer and heart diseases, in a long-term prospective cohort from China," the authors announce. "In this long-term prospective Chinese cohort study, higher plasma vitamin C concentration was associated with lower total mortality, heart disease mortality, and cancer mortality. Our results corroborate the importance of adequate vitamin C to human health."