Kan. News reports about caffeine can be confusing, even though concerns about the popular stimulant are not new, said Karen Hudson, K-State Research and Extension nutrition educator, who also is a registered dietitian. Caffeine is a mild stimulant that affects the nervous system. The Chinese have been brewing tea that contained it for centuries. The American Medical Association defines moderate as 200-300 mg a day, which would be equivalent to the amount of caffeine in one to two cups of coffee. Pregnant women and older adults may be more sensitive to caffeine.
Caffeine can raise blood pressure and the heart rate temporarily.
The rise is similar to an elevation that may result from normal activities, like climbing stairs. Caffeine is not thought to significantly influence an irregular heartbeat. When high blood pressure or an irregular heartbeat are medical concerns, diet and exercise should be monitored by a physician, Hudson said. Either decaffeinated or regular coffee can stimulate stomach acid production. Caffeine is not thought to contribute to miscarriages but does pass from mother to child through the placenta and breast milk.