Extra Antioxidants May Make Little Difference in Lifespan

By Kathryn Doyle

January 08, 2015 (Reuters Health) – People who get a lot of antioxidants in their diets, or who take them in supplement form, don’t live any longer than those who just eat well overall, according to a long term study of retirees in California.
Annlia Paganini-Hill of the Clinic for Aging Research and Education at the University of California, Irvine and colleagues analyzed mailed surveys from the 1980s in which almost 14,000 older residents of the Leisure World Laguna Hills retirement community detailed their intake of 56 foods or food groups rich in vitamins A and C as well as their vitamin supplement intake.
Two-thirds of the original group took vitamin supplements, most often vitamin C. The authors note, though, that the participants’ diets alone were generally more than adequate to meet minimum dietary requirements for vitamin intake.
With periodic check-ins and repeated surveys, the researchers followed the group for the next 32 years, during which time 13,104 residents died.
When Paganini-Hill’s team accounted for smoking, alcohol intake, caffeine consumption, exercise, body mass index, and histories of hypertension, angina, heart attack, stroke, diabetes, rheumatoid arthritis and cancer, there was no association between the amount of vitamins A or C in the diet or vitamin E supplements and the risk of death.
Vitamin users may have different lifestyles or underlying disease states that are related to their risk of death, the authors write.
“In the general population, health-promoting habits often cluster; e.g. those who take vitamin supplements often exercise, do not smoke, and are not obese,” Paganini-Hill told Reuters Health. “Thus, these factors may explain the observed association between longevity and vitamin supplements.”
On the other hand, the authors note, people with unhealthy habits might be more likely to take supplements. For instance, men who were current smokers were about twice as likely to take in high or medium amounts of vitamin C compared to men who had never smoked. A similar pattern held for men’s vitamin A intake and women’s intake of both A and C.
Some large studies have found a connection between vitamin intake and risk of death, but most have not, the study team points out.
“We know quite a lot about how antioxidants act and what they, theoretically, can prevent,” said Sabine Rohrmann of the Institute of Social and Preventive Medicine at the University of Zurich.
“One of the critical issues is that we don’t know very much about how antioxidants act at different concentrations and how they act in humans who have, or who do not have, sufficient vitamin/antioxidant intake,” Rohrmann told Reuters Health by email.
Participants in the new study were largely white, educated and well-nourished.
“We know that the most important factors that influence mortality are smoking and excess body weight,” Rohrmann said. Many studies support the notion that vitamin supplements are usually not necessary because our nutrient intake via a healthy diet is usually sufficient, she said.
Antioxidants can have risks as well. According to the National Institutes of Health, high doses of beta-carotene may increase the risk of lung cancer in smokers, high doses of vitamin E may increase risks of prostate cancer and one type of stroke, and antioxidant supplements may also interact with some medicines.
“Antioxidant supplements should not be used to replace a nutritionally adequate diet,” Paganini-Hill said.
The study was published online December 29 in the American Journal of Epidemiology.
SOURCE: http://bit.ly/1Fgx3a8
Am J Epidemiol 2014.