Carotenoids are neither vitamins nor phytochemicals, but are proving to be very important for health. Dietary carotenoids are thought to provide health benefits in decreasing the risk of disease, particularly certain cancers and eye disease. The carotenoids that have been most studied in this regard are beta-carotene, lycopene, lutein, and zeaxanthin. In part, the beneficial effects of carotenoids are thought to be due to their role as antioxidants. beta-Carotene may have added benefits due its ability to be converted to vitamin A. Carotenoids benefit our skin and reduce cancer risk.
Data from the 1999-2002 National Health and Nutrition Examination Survey (NHANES) indicated that doubling levels of the carotenoids alpha-carotene, beta-carotene, and beta-cryptoxanthin were associated with 2% longer telomeres, DNA sequences at the end of chromosomes that shorten as cells replicate and age.
The findings, published in the European Journal of Nutrition, show only correlation and not causation, and therefore some caution must be exercised when interpreting the data. Despite this, the researchers noted: "[The findings] suggest that carotenoids have a protective effect on telomere loss and that a high intake of these carotenoids may potentially prevent or delay the aging process and age-related diseases."
The aging and lifespan of normal, healthy cells are linked to the so-called telomerase shortening mechanism, which limits cells to a fixed number of divisions. During cell replication, the telomeres function by ensuring the cell's chromosomes do not fuse with each other or rearrange, which can lead to cancer. Elizabeth Blackburn, a telomere pioneer at the University of California San Francisco, likened telomeres to the ends of shoelaces, without which the lace would unravel.
With each replication the telomeres shorten, and when the telomeres are totally consumed, the cells are destroyed (apoptosis). Previous studies have also reported that telomeres are highly susceptible to oxidative stress. Some experts have noted that telomere length may be a marker of biological aging.
The Korean scientists used data from 3660 participants of NHANES and found that blood alpha-carotene, beta-carotene (trans+ cis) and beta-cryptoxanthin were significantly associated with 1.76%, 2.22% and 2.02% longer telomeres, respectively.
On the other hand, blood lutein/zeaxanthin and trans-lycopene did not show any statistical significance, said the researchers.
In addition, compared to the lowest average levels of alpha-carotene, beta-carotene (trans+ cis) and beta-cyptoxanthin, the telomere length increased from 5-8% in the highest average carotenoid levels.
"The role of carotenoid in the protection of telomere loss is biologically plausible," stated the researchers. "Oxygen is essential to life, but too much oxygen is potentially harmful. Although the human body produces oxygen free radicals and other reactive oxygen species as by-products of various metabolic processes, overproduction induces oxidative damage to relevant molecules (DNA, proteins, and lipids), eventually leading to an increased risk of many chronic diseases and aging. Antioxidants have attracted attention as an efficient tool in counteracting oxidative stress. Carotenoids are particularly promising antioxidants, because they are capable of exerting antioxidant protection by scavenging singlet molecular oxygen and peroxyl radicals."
However, the researchers note that there may be a difference between the pro- and non-vitamin A carotenoids, and that additional studies are required to "identify whether there are different effects on protecting the telomere length by specific types of carotenoids".
Commenting on the study‚Äôs findings, CheeYen Lau, nutritionist at carotenoid supplier ExcelVite, said: "It is crucial to preserve the length of telomeres to ensure proper cell functions. The length of the telomere determines the life expectancy of the cell by regulating the number of replications that a cell undergoes.
"The results from this study is very encouraging as high dietary intakes of carotenoids especially alpha-carotene and beta-carotene increase telomere lengths, which suggests reduced aging and risks for age-related diseases or better health."
"This study highlights the importance of attaining high content of carotenoids from natural diets to minimize aging and age-related health problems," added Bryan See, regional product manager, ExcelVite.