Alpha-carotene: the life elixir in carrots
Alpha-carotene, closely related to beta-carotene and found in large quantities in carrots, reduces the mortality rate in adults. In people with a high BMI, a high alpha-carotene intake can almost halve the risk of dying, epidemiologists at the American Centers for Disease Control and Prevention discovered.
The researchers followed about fifty thousand Americans from the period 1988-1994 up to 2006 as part of the Third National Health and Nutrition Examination Survey (NHANES III). At the start of the study the NHANES III participants were 20 or older, and the researchers measured the concentration of alpha-carotene in their blood. In 2006 they determined which participants were still alive, and whether there was a relationship between survival and the previously measured alpha-carotene level.
The best source of alpha-carotene is the common-or-garden carrot. About 75 percent of the alpha-carotene in a western diet comes from carrots. Two hundred grams of cooked carrots contain about 7.5 mg alpha-carotene, and about 16.5 mg beta-carotene.
Like beta-carotene, alpha-carotene can convert into vitamin A, but this happens to a lesser extent than in beta-carotene. Smokers or people who work with asbestos are better off avoiding supplements that contain high amounts of beta-carotene or vitamin A, as they increase their risk of developing lung cancer.
Vitamin A is a hormone that steers process of differentiation in cells, and it's probably a raised vitamin A level that makes beta-carotene supplements risky. However, beta-carotene from food sources has only positive health effects.
The researchers discovered that the higher the level of alpha-carotene in their subjects' blood, the lower their risk of dying, as the figure below shows.
Alpha-carotene had above all pronounced positive cardiovascular effects, as the figure above shows. But in fact, the high alpha-carotene intake reduced the mortality risk for all common causes of death.
When the researchers analysed their data more closely, they noticed that alpha-carotene reduced the mortality risk slightly more in people with a BMI of 30 or higher, in people aged between 45 and 65, and in people with healthy blood pressure. For these groups the reduction in mortality was about a half. But a high alpha-carotene level also reduced mortality by a few dozen percent in other groups too.
If you click on the table below a larger version will appear.
To summarise: alpha-carotene has a positive effect on everything in everybody. And that’s special, say the researchers.
"Our findings showed that serum alpha-carotene concentrations were inversely associated with the risk of death from all causes and death from cardiovascular disease, cancer, and all causes other than cardiovascular disease and cancer", they conclude. "They also showed that the inverse association was independent of demographic characteristics, lifestyle habits, and traditional health risk factors."
Arch Intern Med. 2011 Mar 28;171(6):507-15.
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