Iris (Definition) The iris is a structure within the eye that helps reduce the amount of light that reaches the retina. The iris is known as the colored part of the eye, and can be blue, brown, or any color or combination of colors in between. The iris is the portion of the eye that responds to light stimulation. ...Read more.
Scientists also speculate that caffeine may provide a mood-boosting effect that helps ease pain. Regardless of the mechanism by which it works, the data does indicate that caffeine does indeed make pain medications more effective and help ease pain.
Too Much Caffeine. Consuming too much caffeine can cause chest pain, chest tightness and an increased heart rate. Caffeine affects people differently, depending on weight, normal caffeine consumption and other medical conditions. MayoClinic.com states that the average adult can consume between 200 to 300mg of caffeine daily without causing any harm. If you drink 500mg or more, you may develop adverse reactions, such as chest pain.