As you gaze across the bountiful Thanksgiving offerings on your table this year, be grateful for the life-extending benefits of orange. Orange as in alpha-carotene. Orange as in pumpkin, carrots and squash, the
in this phytonutrient. A
published this week found that people whose blood levels measured highest for alpha-carotene were least likely to die of cancer, cardiovascular disease, or indeed of any cause, during an 18-year period.
Levels of alpha-carotene are likely a surrogate measure for high consumption of fruits and vegetables, generally, since, in addition to the orange foods, dark green vegetables (such as broccoli, green beans, peas, spinach, kale, collard greens and lettuce) are also high in alpha-carotene. Even after accounting for body mass index (BMI) and for lifestyle factors such as smoking, exercise and alcohol consumption, the relationship between alpha-carotene and survival held steady: the more alpha-carotene in the blood, the greater the likelihood of being alive throughout the study period.
Nutritionists long believed it was
, a phytonutrient plentiful in green leafy vegetables, that was exerting this healthful effect. But ever since large
that supplementation with beta-carotene did not appear to confer particular benefits (and for smokers, appeared to increase
), researchers have been hunting for the magic nutrient in plants that does boost immunity, maintains cardiovascular health and suppresses cancer development.
This large study was published Monday in the Archives of Internal Medicine. Added to a number of smaller studies that have teased out a key role for alpha-carotene, this one suggests researchers may have found their nutritional champion. Head-to-head comparisons with beta-carotene suggests that alpha-carotene is far more powerful in inhibiting the proliferation of brain cancer cells, suppressing progression of liver cancer and preventing the development of cancers of the lung and skin.
Researchers from the
looked at a population of 15,318 adults with an average age of 45 who provided blood samples between 1988 and 1994, and who were tracked until 2006. In all, 3,810 of the study participants died in the course of the period. Those in the group with the lowest blood concentrations of alpha-carotene were about 26% more likely to have died during the study period than were those with the highest levels of the nutrient in their blood.
The CDC researchers suggested that ideal levels of alpha-carotene seem to come from food, rather than a pill. Very high levels--the kind one might get from taking an alpha-carotene supplement--appear to protect against cardiovascular disease. But they "may be less effective than lower concentrations against death from cancer," the researchers wrote.