Understanding Caffeine Sensitivity

Caffeine is a substance that stimulates the body’s central nervous system, helping you feel more awake and giving you a boost of energy. It comes from natural sources like coffee beans, cacao, and tea leaves, and is commonly added to foods, drinks, and medications.

Many people consume at least one caffeinated beverage daily, and some are more sensitive to caffeine than others. This means they experience intense or unwanted side effects after relatively low doses of caffeine, such as headache, restlessness, dizziness, or trouble sleeping.

This article provides an overview of caffeine sensitivity and reasons why the stimulant affects people differently.

What Is Caffeine Sensitivity?

Moderate caffeine consumption is linked to feeling more awake, alert, and energetic. Caffeine sensitivity refers to how strongly a person feels those impacts after consuming it.

For example, drinking a cup of coffee in the morning may be way too much for one person, while another person may need three or four cups of coffee to experience caffeine's effects.

While there's no specific test to measure caffeine sensitivity, experts have loosely defined it into three categories based on how the body metabolizes (processes) caffeine.

Normal Sensitivity

Most people likely fall into the category of normal caffeine sensitivity. It means they're able to consume up to 400 milligrams of caffeine (roughly four to five cups of coffee) without experiencing negative side effects. This amount is the Food and Drug Administration's (FDA's) recommended daily caffeine intake limit and appears to be safe for most healthy adults.

Hyposensitivity (Low Sensitivity)

People with low sensitivity to caffeine can take in even higher doses of caffeine without experiencing negative side effects. They can also usually consume caffeine before bed without having any sleep disruptions.

For people in this group, the body metabolizes (processes) caffeine quickly. One study estimates that roughly 10% of the population carries a gene linked to low caffeine sensitivity.

Hypersensitivity (High Sensitivity)

People with a high caffeine sensitivity metabolize the stimulant more slowly.

Having a high or heightened sensitivity to caffeine means you likely experience an intense reaction to small doses of caffeine, such as:

• Insomnia
• Increased heart rate
• Restlessness
• Headache

In this group, one cup of coffee may feel like four cups, and can cause issues falling asleep at night.

Symptoms

When caffeine is consumed in moderation, its desired effects can include mood enhancement, alertness, improved focus, and quicker processing times.

But when caffeine intake exceeds a person’s sensitivity level, it can lead to unwanted side effects. These can develop as soon as several minutes after consuming it. They include:

• Headaches
• Anxiety
• Dizziness
• Rapid or irregular heartbeat
• Restlessness and shakiness
• Insomnia (trouble sleeping)
  
• Diuresis (increased urination)
• Upset stomach
• Muscle twitching
• Flushed face
  

Diagnosis

There's currently no medical test to check for caffeine sensitivity. But if you're planning on speaking to a healthcare provider about your caffeine intake and sensitivity level, it may be worth monitoring at home by:

• Keeping a daily log of food, drink, and medication intake to determine if you may actually be taking in more caffeine than you realize.
• Checking labels closely on food products, drinks, and medications, as caffeine is sometimes included in many less-obvious items.
• Slowly and carefully reducing your caffeine consumption for a few days to see if this affects your symptoms, which could help reveal if caffeine sensitivity is truly the cause.

Common Causes

Experts have found that several factors can play a role in determining how your body reacts to caffeine.

Liver Metabolism

Caffeine is metabolized (broken down) in the liver by an enzyme (protein) known as CYP1A2. The gene associated with this enzyme helps predetermine how sensitive a person may be to caffeine consumption. Studies have found people with a high caffeine sensitivity don't produce as much CYP1A2.

Medications

Some medications and supplements can interact with caffeine sensitivity. This can make caffeine side effects more intense.

Research suggests that a medication used to treat asthma known as theophylline, and echinacea, an herbal supplement thought to help cold symptoms, can increase the effects of caffeine in the body.

Check with a healthcare provider or pharmacist if you think medications may be interfering with how your body processes caffeine.

Genetics

Research has shown that a person's genetic makeup has a lot to do with how they respond to caffeine.

In addition to the CYP1A2 gene that influences how quickly the liver breaks down caffeine, another gene known as ADORA2A impacts how the central nervous system (communication between the brain and body) reacts to caffeine's stimulating effects. People who have a variation of the ADORA2A gene are likely to have a high sensitivity to caffeine that affects their sleeping pattern.

Risk Factors

Caffeine sensitivity varies greatly by individual. But in general, there are several factors that can potentially make a person more susceptible to high caffeine sensitivity. These include:

• Older age
  
• Female sex
• Certain chronic health conditions
• Smoking
• Oral contraceptive (birth control) use
  

How Much Caffeine Is Recommended?

For most healthy adults, the FDA recommends no more than 400 milligrams of caffeine a day, which equals about four or five cups of coffee. That's the amount that the agency has found is generally not associated with any negative health effects.

There are no current federal recommendations on caffeine intake for children or adolescents. Experts generally discourage caffeine consumption in those ages 12 and younger, and suggest a very limited caffeine intake in those ages 12–18.

Caffeine Alternatives

Frequent caffeine consumption may lead to a physical or psychological dependence on it.

If coffee is part of your daily ritual, and you're looking to replace it with a lower caffeine or caffeine-free option, consider the following alternatives:

• Yerba mate tea
• Matcha tea powder
• Chai tea
• Chicory root coffee
• Maca root powder
• Dandelion root tea
• Warm lemon water
• Herbal or rooibos tea
• Smoothies
• Golden milk (made with milk and spices like turmeric)
• Carob powder (a replacement for cacao powder)
• Cordyceps (a fungi that is regarded as an energy booster)

Keep in mind that there is still some caffeine in decaffeinated coffee. An 8-ounce cup of brewed decaf coffee can have anywhere from 1 to 25 milligrams of caffeine. Chai tea and Matcha tea powder also contains caffeine, just not as much as is in coffee.

Summary

Caffeine is a stimulant that acts on the body's central nervous system. While it's usually linked to improved energy, cognition, and mood, consuming too much can interfere with sleep, make you feel restless, and even affect your heart rate.

Some people are more sensitive to caffeine than others and experience negative effects even at very low doses. Research shows that genetics play a large part in how the body processes the stimulant, which determines a person's caffeine sensitivity. Though they may be unpleasant, caffeine sensitivity symptoms usually aren't harmful and can be addressed by reducing or eliminating caffeine.

A Word From Verywell

Caffeine affects everyone differently, no matter which caffeine sensitivity category you fall in. If you're experiencing any discomfort with your daily caffeine intake, slowly reducing your consumption can help. Check with a healthcare provider or other trusted community health source if you have concerns about how caffeine may be affecting you.