Use of caffeine has also been associated with difficulty conceiving, according to a study by epidemiologists Elizabeth Hatch, of the National Cancer Institute in Rockville, Md., and Michael Bracken of the Yale University School of Medicine. Some scientific studies also have discovered that caffeine, consumed in excess, can interfere with DNA duplication, causing mutations in cell reproduction, which results in genetic defects, cancers and tumors . Its use has also been found to exacerbate existing anxiety disorders, and may be the cause of some panic attacks. As with other drugs, caffeine produces in its subjects a level of tolerance, or acquired insensitivity to the drug. Although dependence upon caffeine in itself is not dangerous, an increased tolerance level often leads to increased usage, which, if dramatic, can cause serious effects.
Benefits Used in moderation, caffeine has no detrimental effects upon human health.
In some uses it has proven beneficial. In the process of en vitro ferilization, caffeine improves the fertility rate by increasing the motility of sperm, researchers at the University of Pennsylvania School of Medicine have discovered. And the drug's ability to increase both mental alertness and physical endurance is helpful in many occupations in which physical endurance, rather than fine motor coordination, is required. T he US has the 12th highest per capita coffee consumption in the world. It is the top agricultural import of North America, where caffeine consumption exceeds three times the world average.