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Alpha-Carotene Tied to Lower Mortality Risk

People who consume high levels of alpha-carotene -- which is found in several vegetables -- may live longer, researchers found.

Medpage Today, Todd Neale, Nov 22, 2010

People who consume high levels of alpha-carotene -- which is found in several vegetables -- may live longer, researchers found.

Among participants of the National Health and Nutrition Examination Survey (NHANES), greater serum concentrations of the compound were associated with lower risks of dying during follow-up (P<0.001 for trend), according to Chaoyang Li, MD, PhD, 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."

Action Points  

  • Note that higher levels of alpha-carotene, found in some vegetables, were associated in this study with reduced risk of dying from a number of causes.

  • Point out also that the study is subject to residual confounding owing to unmeasured factors and therefore cannot prove causality.

All of the carotenoids -- mainly consumed in fruits and vegetables and through supplements -- are antioxidants, 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.

The average serum concentration of alpha-carotene at baseline was 4.79 µg/dL.

Through a mean follow-up of 13.9 years, there were 3,810 deaths.

The likelihood of death was inversely associated with serum alpha-carotene levels after adjustment for demographics, lifestyle habits, and health risk factors. Compared with a level of 0 to 1 µg/dL, the relative risks of death for increasing concentrations were as follows:

  • 2 to 3 µg/dL -- RR 0.77 (95% CI 0.68 to 0.87)
  • 4 to 5 µg/dL -- RR 0.73 (95% CI 0.65 to 0.83)
  • 6 to 8 µg/dL -- RR 0.66 (95% CI 0.55 to 0.79)
  • 9 µg/dL or higher -- RR 0.61 (95% CI 0.51 to 0.73)

The trend was consistent in most subgroups, with the exception of participants ages 20 to 44, Mexican Americans, those who did not exercise at all, those with a body mass index from 25 to 29.9, those with low HDL cholesterol, and those with a low beta-carotene concentration.

The relationship also persisted for death from cardiovascular disease, cancer, and all other causes (P<0.05 for all).

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 proliferation of human neuroblastoma cells, the tumor-promoting action of glycerol in lung carcinogenesis, and skin tumor promotion. It has also been found to be a potent inhibitor of liver carcinogenesis.

"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.

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