Vegetables such as carrots, sweet potatoes, pumpkins and winter squashes - are all packed with alpha-carotene, a carotenoid that has been found to help to fight off disease.

High blood levels of this beneficial antioxidant are associated with a reduced risk of dying over a 14-year period, according to a new report.

Carotenoids such as beta-carotene, alpha-carotene and lycopene - are produced by plants and microorganisms and act as antioxidants, fighting off oxygen-related damage in the body. The damage to DNA, proteins and fats is thought to play a role in the development of chronic diseases like heart disease and cancer.

Carotenoids in the human body are obtained mainly through eating fruits and vegetables rich in the nutrients, or through supplements.

Although studies suggest eating more fruits and vegetables is associated with lower risk of chronic diseases, randomized controlled trials have not shown any benefit for Beta-carotene supplements, as the authors note in the report: "Therefore, carotenoids other than Beta-carotene may contribute to the reduction in disease risk, and their effects on risk of disease merit investigation."

Study Details

The scientists assessed the relationship between alpha-carotene and the risk of death among 15,318 adults age 20 and older who participated in the Third National health and nutrition Examination Survey Follow-up Study. Participants underwent a medical examination and provided blood samples between 1988 and 1994, and were followed through 2006 to determine whether and how they died.

Of the participants roughly a quarter - 3,810 - died.

Researchers found those with higher levels of blood alpha-carotene levels had a lower risk of death from cardiovascular disease or cancer. In fact, as the level of alpha-carotene went up, the risk of dying went down dramatically.

"The association between serum alpha-carotene concentrations and risk of death from all causes was significant in most subgroups stratified by demographic characteristics, lifestyle habits and health risk factors," the authors write.

Alpha-carotene is chemically similar to Beta-carotene but may be more effective at inhibiting the growth of cancer cells in the brain, liver and skin, they note.

"Moreover, results from a population-based case-control study of the association between the consumption of fruits and vegetables and risk of lung cancer suggest that consumption of yellow-orange (carrots, sweet potatoes or pumpkin and winter squash) and dark-green (broccoli, green beans, green peas, spinach, turnips greens, collards and leaf lettuce) vegetables, which have a high alpha-carotene content, was more strongly associated with a decreased risk of lung cancer than was consumption of all other types of vegetables," the authors write.

The results support increasing fruit and vegetable consumption as a way of preventing chronic diseases which can lead to premature death.

Research Paper Details:

Li C, Ford ES, Zhao G, et al. Serum {alpha}-Carotene Concentrations and Risk of death Among US Adults The Third National health and nutrition Examination Survey Follow-up Study. Arch Intern Med., November 22, 2010.