You become lazy
A nine-month long study of 40 male rats conducted by researchers at the University of British Columbia, Canada, suggests that coffee may result in workers getting lazier. Researchers say the findings may apply to humans as well, especially people who use stimulants to stay alert for a long period of time, such as long-distance truck drivers.
You feel jumpy
People drink coffee to boost their alertness. Caffeine increases adrenaline levels, and when taken in high enough amounts — and these amounts vary from one person to another — jittery sensations are not uncommon, and people may feel jumpy, according to the FDA. Getting jitters and tremors as a result of excessive coffee consumption even has a name — caffeinism.
You get muscle spasms
Studies conducted so far do not establish a definitive link between caffeine and muscle cramps, but some research shows a possible connection. Stimulants can cause any muscle in the body to twitch, and coffee is a stimulant. Caffeine triggers the nervous system, which controls the contraction of skeletal muscle through nerve cells. Consumed in high amounts, caffeine can cause involuntary spasms of muscle fibres across the body, according to research out of Radboud University Nijmegen Medical Centre in the Netherlands.
You have diarrhea
Digestive issues, more specifically diarrhea, are possible side effects of drinking too much coffee. Coffee, and other beverages that have caffeine, may have a laxative effect in some people, if you drink more than three cups a day.
You have iron deficiency
Coffee — or the caffeine in it — has been shown to interfere with the body’s absorption of iron. Skipping tea and coffee drinks with meals is a common advice for anemic people. Hemoglobin, a protein in red blood cells that carries oxygen throughout the body, contains iron. Iron deficiency means less oxygen gets to the body’s cells, resulting in fatigue, weakness, and pale skin.