Effects of Caffeine on the Body 

effects of caffeine

Caffeine is a substance that stimulates the central nervous system. In doing so, it affects the body in several ways. Many people get caffeine from coffee and certain teas, soda, or energy drinks. You’ll also find it in some foods and even as an ingredient in various prescription and over-the-counter medications. 

Many of caffeine’s effects are positive but consuming too much of it or cutting back on your regular caffeine intake too quickly can have adverse effects. Consequently, you should learn about how the body reacts to it.  

How Much Caffeine Is Too Much?

Everyone’s tolerance for caffeine is different. But generally speaking, it’s safe for healthy adults to consume up to 400 milligrams of caffeine per day. 

Using coffee as an example, an 8-ounce cup has 95 to 165 milligrams of caffeine. As you do the math on your coffee and caffeine consumption, keep in mind that an average size mug can hold 12 ounces or more. Also, many people are surprised to learn that light roast coffee has more caffeine than dark roast. 

If you’re a tea drinker, 8 ounces of black tea has 25 to 48 milligrams of caffeine, and an 8-ounce cup of green tea has 25 to 29 milligrams. 

Positive and Negative Effects of Consuming Caffeine

Researchers continue to study caffeine’s effect on the body, but studies suggest that if you consume an amount of caffeine that’s within the recommended range, you may experience these benefits:

  • Increased energy level and alertness almost immediately
  • Lower risk of type 2 diabetes
  • Support for brain health
  • Lower risk of depression 
  • Decreased suicide risk (as much as 45% lower)
  • Protection from certain liver conditions
  • Lower risk of oral and throat cancers
  • Better heart health
  • Increased longevity

On the other hand, caffeine consumption (especially overconsumption) is associated with:

  • Diarrhea
  • Fertility issues
  • Miscarriage and developmental problems in newborns
  • The jitters
  • Worsening of anxiety and sleep disorders
  • Decreased calcium absorption in the bones
  • Nausea and vomiting
  • Heartburn
  • Rapid heartbeat

People also often ask about caffeine’s effects on blood vessels. Does caffeine increase blood pressure? It can cause a temporary increase, which can be especially noticeable if you consume caffeine right before vigorous physical activity. 

If you consume caffeine regularly and then suddenly cut back on the amount, you may experience:

  • Headaches
  • Muscle aches 
  • Irritability

How Long Does Caffeine Stay in Your System?

Caffeine’s effects tend to peak 30 to 60 minutes after consuming it but can continue for many hours. It has a half-life (meaning the time it takes for the amount present in your body to be reduced by half) of five hours. So, if you consume 100 milligrams of caffeine, five hours later, 50 milligrams will still be in your body. 

The remainder stays in your system significantly longer. People who are particularly sensitive to caffeine can feel its effects for many hours or even a few days. Sleep experts recommend that you stop consuming caffeine at least six hours before bedtime

Talk with Your Doctor About Caffeine

Should you consume more caffeine? Less? None? Should you have some in the morning? Use it for an energy boost in the afternoon? Ultimately, there are many factors to consider, including your overall health and health goals, your sensitivity to caffeine, and others. 

If you have questions or concerns about your caffeine consumption, your Baptist Health physician is happy to answer them in the context of their knowledge of your health. If you don’t have a Baptist Health physician, you can find one near you in our online provider directory


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