People who consume high levels of alpha-carotene -- an antioxidant found in orange and green vegetables -- may live longer, researchers found.
Among participants of the National Health and Nutrition Examination Survey (NHANES), higher serum levels of alpha-carotene were associated with a lower risk of death, according to Dr. Chaoyang Li of the CDC's Division of Behavioral Surveillance in Atlanta and colleagues.
The relationship held true for death from cancer, cardiovascular disease, and all other causes, the researchers reported online in Archives of Internal Medicine.
The findings add "further support to previous findings that fruit and vegetable consumption is beneficial to people's health," they wrote. "Our results, if replicated in other studies and populations, suggest a need for clinical research into the health benefits of serum alpha-carotene."
All of the carotenoids -- mainly consumed in fruits and vegetables and through supplements -- are believed to delay or prevent oxidative damage involved in some chronic diseases, including cancer and cardiovascular disease.
Although there has been much research into the relationship between beta-carotene and risk of disease, less attention has been paid to the role of alpha-carotene, which is found in high concentrations in yellow-orange vegetables such as carrots, sweet potatoes, and pumpkins and dark-green vegetables such as broccoli, spinach, and leaf lettuce.
Li and colleagues looked at the association between serum levels of alpha-carotene and mortality using data from the Third NHANES Follow-up Study, conducted from 1988 to 1994. The analysis included 15,318 adults ages 20 and older.
Although randomized clinical trials of beta-carotene supplementation have not demonstrated a benefit for reducing either the incidence of or mortality from cancer and cardiovascular disease, there are some differences between alpha-carotene and beta-carotene that might warrant further study.
The two compounds are chemically similar, but studies have found that alpha-carotene is better at inhibiting the several aspects of tumor formation.
"Future research is warranted to elucidate the mechanisms underlying the differential effects of alpha-carotene and beta-carotene against cancer and cardiovascular disease," Li and colleagues wrote.
They acknowledged some potential limitations of the study, including the use of a baseline measure of alpha-carotene concentration only, possible misclassification of the cause of death, and potential residual confounding from unmeasured factors.