While coffee may increase alertness for many, for some people, it can make them tired. This may be due to a tolerance to caffeine or how caffeine affects chemicals in the brain.
Caffeine is the
Some people, for example, can drink multiple cups during the day and experience few effects. Others may experience adverse effects after drinking a single cup of coffee.
According to the
In this article, we look at why coffee makes some people feel tired. We also discuss other potential effects of coffee and daily intake recommendations.
Coffee itself does not make people tired, but the caffeine in coffee and its effects on the body can sometimes cause tiredness.
Some reasons that drinking a cup of coffee might make someone feel tired include the fact that:
Caffeine blocks adenosine receptors in the brain
Adenosine is a brain chemical that
Normally, adenosine molecules bind to special receptors in the brain, which slows down brain activity in preparation for sleep. However, caffeine prevents this from happening by binding to adenosine receptors.
The body rapidly absorbs caffeine, so people may feel its effects within minutes. In fact, the body absorbs
The length of time caffeine stays in the body varies from person to person. Although it blocks adenosine receptors, it does not affect the production of new adenosine molecules.
When caffeine wears off, adenosine molecules can bind to their receptors, which can cause sleepiness.
Some people build a tolerance to caffeine
People who regularly consume coffee and other caffeinated beverages can develop a tolerance to it. Since caffeine blocks adenosine receptors, the body produces more adenosine receptors to counteract the effects of frequent caffeine consumption.
At the start of the study, the participants had higher heart rates and exerted greater cycling power after drinking caffeine. After 15 days, however, the effects of the caffeine began to decrease.
Given these results, it appears that people who regularly consume caffeine may build up a tolerance to its stimulant effects.
However, other research has suggested that continuous exposure to caffeine
Caffeine increases blood sugar levels
Coffee’s effects on blood sugar levels remains a point of controversy for researchers.
In a small study, researchers observed that consuming 100 mg of caffeine adversely affected glucose metabolism in 10 healthy males with excess weight.
These findings suggest that caffeine, not coffee itself, can impact glucose metabolism, which can raise blood sugar levels.
People with high blood sugar may experience headaches, fatigue, trouble concentrating, increased thirst, or frequent urination until their blood sugar levels return to normal.
Coffee can affect more than a person’s energy levels. The sections below discuss a few possible effects of drinking coffee.
People who drink coffee before going to bed may have trouble falling asleep.
The authors of a
In people with panic disorders and depression, high doses of caffeine can trigger anxiety-related symptoms.
There may be
However, current research suggests that mild-to-moderate coffee consumption may protect heart health.
However, the findings of a
The authors of a
Also, research from 2019 found that coffee compounds — including caffeine, trigonelline, and chlorogenic acid — protect against gastrointestinal and liver cancer progression.
However, more research is necessary to confirm the links between drinking coffee and cancer risk.
Other effects of drinking coffee
Other potential effects of drinking coffee include:
- increased alertness
- jitteriness or restlessness
- stomach pain
- frequent urination
Although no official guidelines exist for children and adolescents,
In pregnant women, caffeine can stay in the body up to
If drinking a cup of coffee makes a person feel tired, the effects of caffeine may be responsible.
Caffeine increases alertness by interfering with certain chemical processes in the brain that regulate the sleep-wake cycle. However, once the body completely metabolizes caffeine, it can make people feel tired.
The rate at which a person’s body metabolizes caffeine varies depending on genetic and lifestyle factors.
People who drink coffee every day may develop a tolerance to caffeine’s stimulant effects, which means that they need to drink more of it if they want to experience similar results.