For years, scientists have been searching for health risks associated with caffeine consumption. In general, the research has some confounding findings and many of the caffeine-associated health risks occurred only with exceedingly high caffeine intakes. However, there are some adverse effects associated with caffeine that may make you consider cutting back. Probably one of it's most famous effects, too much caffeine can make you nervous, irritable, and cause insomnia. Caffeine can cause heartburn by relaxing the sphincter between the esophagus and stomach, allowing reflux of stomach acids.
Caffeine can also aggravate stomach ulcers by increasing stomach acid production.
Problems of constipation, diarrhea and gastrointestinal upset have all been associated with caffeine consumption. Caffeine can intensify certain heart rhythm problems and cause a temporary rise in blood pressure. In addition, unfiltered coffee, such as espresso can cause increases in total cholesterol levels. Caffeine also increases loss of calcium and decreases calcium absorption, which could contribute to the development of osteoporosis . This adverse effect is most pronounced when calcium intake is inadequate.