Can Dietary Alpha-Carotene Increase Longevity?

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For many years there has been growing evidence that eating more fruits and vegetables reduces the risk of cancer, heart disease and other chronic ills. Carotenoids are plant chemicals with anti-oxidant properties that give many fruits and vegetables their yel- low, orange and red color. For several years beta-carotene supplements became very popular in part because of claims they could be beneficial for reducing the risk of cancer. Unfortunately, randomized controlled trials failed to show any benefit for beta-carotene supplements and two large studies actually found a significant increased risk of dying and particularly from lung cancer in smokers. However, the fact that beta-carotene supplements failed to reduce disease and help people live longer did not negate other data show- ing that something in fruits and vegeta- bles reduces disease and increase life expectancy. So while high doses of beta-carotene supplements are clearly of no benefit and appear harmful at least to smokers it is possible another carotenoid or perhaps a mix of them could reduce disease risk.

With that in mind, Dr. Chaoyang Li at the Centers for Disease Control and Prevention decided to look at the impact of higher levels of alpha-carotene in the blood of 15,318 adults who participated in a national study. The subjects underwent a medical examination and provided blood samples between 1988 and 1994, and were then followed through 2006 to determine their risk of death and disease. During the follow-up period 3,810 participants died and Dr. Li’s group found the risk for dying was significantly lower for individuals with higher levels of alpha- carotene in their blood. Individuals with the lowest blood alpha-carotene levels (<1mcg/dl), had a risk of death 39% lower than those with levels of 9mcg/ dl or higher. Higher alpha-carotene in the blood appeared to be associated with lower risk of dying from both cardiovascular disease and cancer. This study will appear March 28, 2011 print issue of Archives of Internal Medicine.

This study’s results are consistent with data from population-based case-con- trol studies looking at the consumption of fruits and vegetables and the risk of lung cancer which found more carrots, sweet potatoes or pumpkin and winter squash, broccoli, green beans, peas, and green leafy vegetables (all with a high alpha-carotene content) were the most strongly associated with a decreased risk of lung cancer than other vegetables or fruits. Most of these are high in beta-carotene as well.

Bottom Line: The results of this study support increasing alpha-carotene-rich vegetable consumption as a way to reduce serious illness and increase life expectancy but they most certainly do not prove that alpha-carotene supplements can do the same.

By James J. Kenney, PhD, RD, FACN

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