Coffee or beer? Your choice could affect your lifespan The substances influence the length of telomeres - the end parts of DNA Telomeres get shorter as a person ages, when they're too short, the cell dies Shorter telomeres are associated with poor health and an increased chance of premature death Caffeine was found to shorten telomeres, but alcohol lengthened them Next time you congratulate yourself for choosing a coffee over a beer, you might want to think again. Researchers have discovered that caffeine can shorten life expectancy, while alcohol can increase it. Scientists at Tel Aviv University found that caffeine shortens, and alcohol lengthens, telomeres - the end parts of chromosomal DNA. Researchers have discovered that caffeine can shorten life expectancy while alcohol can increase it Just as the plastics tips of shoelaces prevent fraying, telomeres keep chromosomes stable and prevent deterioration when the cells containing them divide. Telomeres become shorter as a person gets older as every time a cell duplicates, the chromosomes are copied into the new cell with slightly shorter telomeres. When the telomeres become too short, the cell dies. Shorter telomeres are associated with poor health and an increased chance of premature death. "For the first time we've identified a few environmental factors that alter telomere length, and we've shown how they do it," said Professor Martin Kupiec. What we learned may one day contribute to the prevention and treatment of human diseases. The researchers set out to establish if different environmental factors had an impact on telomere length in yeast cells. The substances influence the length of telomeres (pictured in yellow) which are the end parts of chromosomal DNA and which usually shorten with age They found temperature and pH changes had no effect. However, they found that telomere length was reduced by even low levels of caffeine, while it was increased by alcohol. The researchers say that even an espresso contains enough caffeine to affect telomere length, as does five per cent ethanol solution. To understand these changes, the researchers scanned 6,000 strains of the yeast, each with a different gene deactivated. They then conducted genetic tests on the strains with the longest and shortest telomeres, revealing that two genes, Rap1 and Rif1, are the main players controlling environmental factors and telomere length. In total, some 400 genes interact to maintain telomere length, they noted, underscoring the importance of this gene network in maintaining the stability of the genome. Strikingly, most of these yeast genes are also present in the human genome. "This is the first time anyone has analysed a complex system in which all of the genes affecting it are known," said Professor Kupiec. It turns out that telomere length is something that's very exact, which suggests that precision is critical and should be protected from environmental effects.