Serum Antioxidant Nutrients, Vitamin A, and Mortality in US Adults
Abhishek Goyal Cancer Epidemiol Biomarkers Prev Published OnlineFirst July 29, 2013
Observational studies have suggested that antioxidant nutrients may reduce cancer and overall mortality risks. However, most randomized trials have failed to demonstrate survival benefits. Examining non-linear associations between antioxidant levels and health outcomes may explain these discrepant findings. Methods: We evaluated all-cause, cancer and cardiovascular mortality risks associated with quintiles (Q1-Q5) of serum antioxidant (vitamins C and E, beta-carotene, and selenium) and vitamin A levels, in 16,008 adult NHANES III (The Third National Health and Nutrition Examination survey, 1988-1994) participants.
Results: Over a median follow-up period of 14.2 years, there were 4,225 deaths, including 891 from cancer, and 1,891 from cardiovascular disease. We observed a dose-response decrease in cancer and overall mortality risks with higher vitamin C levels.
In contrast, for vitamin A, risk of cancer death decreased from Q1-Q2, with no further decline in risk at higher levels.
For vitamin E, having levels in Q4 were associated with the lowest cancer mortality risk.
Both vitamin A and E had U-shaped associations with all-cause mortality. Cancer mortality risks decreased from Q1-Q2 for beta-carotene and from Q1-Q4 for selenium. However, for beta-carotene and selenium, overall mortality risks decreased from Q1-Q2 but then did not change significantly with higher levels.
Conclusions: Antioxidant supplement use should be studied in the context of overall mortality and other competing mortality risks. Impact: These data suggest the possible use of novel intervention studies where doses of these agents are individualized based on serum levels, and possibly, markers of oxidative stress and systemic inflammatory response.
