Caffeine is a mind-altering drug common in foods and beverages. While most people are familiar with the buzz and alert feelings that immediately follow a cup of coffee, not everyone understand the complex biological reactions that caffeine causes in the body. Caffeine is absorbed in the body very quickly, and can have an immediate effect on your central nervous system.

Caffeine and the Body

Caffeine is quickly absorbed into the body and is immediately distributed to the brain, according to Medline Plus. Unlike some chemicals, caffeine does not accumulate in the bloodstream or other parts of the body, but is instead excreted in urine within a few hours of consumption. As caffeine passes through the brain, signals are sent to the adrenal glands that cause them to pump stress hormones through your body in the imitation of a fight-or-flight response.

Speed

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Determining an exact speed or time for caffeine absorption is difficult due to individual factors such as age, body weight, caffeine sensitivity and diet. However, according to the ABC website, women metabolize caffeine at a rate 20 to 30 percent quicker than men. As your blood transfers the caffeine from your gastrointestinal tract to your brain, it increases your total metabolic rate, reaching its maximum concentration within an hour of consuming.

Effects

Although caffeine is widely available in products ranging from sodas to chocolate and coffee, the Teen’s Health website recommends capping your dosage to 300 milligrams a day 2. As caffeine begins to stimulate your central nervous system, feelings of awareness, energy and elevated mood can often occur, followed by a crash of low energy and tiredness. Due to its addictive properties, caffeine can form dependencies and addictions in individuals who consume as little 100 milligrams a day, leading to withdrawal symptoms such as tiredness, irritability and headaches.

Safety Concern

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Reduce your risk of negative symptoms by limiting your caffeine intake, and never drinking caffeinated beverages on an empty stomach. If you feel that you may be dependent on caffeine, talk to your doctor about healthy alternatives to your eating and drinking habits.