Some people just can’t seem to function until after having their first cup of coffee in the morning. The National Coffee Association suggests that over half (54%) of American adults are regular coffee drinkers (1). That doesn’t take into account tea drinkers, or people who consume other caffeinated beverages, such as colas.
That is a lot of caffeine, so it is worth taking some time to learn about what caffeine is, and how it affects you in the short and in the long term. While caffeine is known to have proven benefits with moderate consumption, over-consumption could cause many health issues in the long run.
What is Caffeine?
Caffeine is a chemical stimulant called trimethylxanthine, and when it is in its pure form, it is a white crystalline powder (2). It is produced naturally in certain plants, but it can also be made synthetically.
Pure caffeine is a bitter substance naturally found in coffee beans, tea, sodas, cocoa, chocolate, and energy drinks. It is also an additive in some prescription and non-prescription drugs.
Caffeine is the most widely consumed drug in the world. It is referred to as a drug since it has the capacity to cause addiction. Of course, the effects of caffeine are much milder than other drugs, but for those who are addicted, the habit is very hard to get over.
How Does Caffeine Work?
After you drink coffee, tea, or another food or drink with caffeine, it is absorbed in the stomach completely after 45 minutes. Caffeine concentration in the blood can reach its peak anywhere between 15-120 minutes after consumption (3).
Caffeine is molecularly similar to a chemical naturally present in the human body called adenosine. In normal conditions, adenosine is a suppressant that binds to nerve cells, and it helps to promote sleep and a calm mind. It also causes blood vessels to dilate, which, in turn, increases oxygen consumption when we are calm and asleep (3).
However, to a nerve cell, caffeine looks like adenosine, and it binds to the nerve cell’s adenosine receptors. Unlike adenosine, caffeine doesn’t suppress cell activity. Caffeine binds to all or most of the adenosine receptors, and the cells can no longer detect adenosine, so cell activity speeds up rather than slowing down (3).
The increased activity is perceived as an “emergency” by the brain, and it activates the release of the hormone adrenaline.
Adrenaline is the reason for many of the changes in the body associated with caffeine consumption, like:
Pupil dilation
Rapid breathing
Increased heartbeat
Increased blood pressure (because of the restricted blood vessels)
Decreased blood flow to the stomach (which may be perceived as a suppressed appetite)
Increased energy
Tight muscles (3)
How Much Caffeine is in Coffee?
The Center for Science in the Public Interest published information that reported the caffeine content in coffees, teas, foods and some drugs, with the goal of informing the public on what they are consuming (4).
First, let’s take a look at some common coffees, ordered from most to least caffeine:
Table 1: Caffeine in Coffee Varieties
Coffees
Serving Size
Caffeine (mg)
Dunkin’ Donuts Coffee with Turbo Shot
large, 20 fl. oz.
436
Starbucks Coffee
venti, 20 fl. oz.
415
Starbucks Coffee
grande, 16 fl. oz.
330
Panera Frozen Mocha
16.5 fl. oz.
267
Starbucks Coffee
tall, 12 fl. oz.
260
Starbucks Caffè Americano
grande, 16 fl. oz.
225
Panera Coffee
regular, 16.8 fl. oz.
189
Starbucks Espresso Frappuccino
venti, 24 fl. oz.
185
Dunkin’ Donuts Coffee
medium, 14 fl. oz.
178
Starbucks Caffè Mocha
grande, 16 fl. oz.
175
Starbucks Iced Coffee
grande, 16 fl. oz.
165
Maxwell House Ground Coffee—100% Colombian, Dark Roast, Master Blend, or Original Roast
2 Tbs., makes 12 fl. oz.
100-160
Dunkin’ Donuts Cappuccino
large, 20 fl. oz.
151
Starbucks—Caffè Latte, Cappuccino, or Caramel Macchiato
grande, 16 fl. oz.
150
Starbucks Espresso
doppio, 2 fl. oz.
150
Keurig Coffee K-Cup, all varieties
1 cup, makes 8 fl. oz.
75-150
Folgers Classic Roast Instant Coffee
2 tsp., makes 12 fl. oz.
148
Starbucks Doubleshot Energy Coffee, can
15 fl. oz.
146
Starbucks Mocha Frappuccino
venti, 24 fl. oz.
140
Starbucks VIA House Blend Instant Coffee
1 packet, makes 8 fl. oz.
135
McDonald’s Coffee
large, 16 fl. oz.
133
Maxwell House International Café, all flavors
2⅔ Tbs., makes 12-16 fl. oz.
40-130
Seattle’s Best Coffee—Iced Latte or Iced Mocha, can
9.5 fl. oz.
90
Starbucks Frappuccino Coffee, bottle
9.5 fl. oz.
90
International Delight Iced Coffee
8 fl. oz.
76
Maxwell House Lite Ground Coffee
2 Tbs., makes 12 fl. oz.
50-70
Dunkin’ Donuts, Panera, or Starbucks Decaf Coffee
16 fl. oz.
15-25
Maxwell House Decaf Ground Coffee
2 Tbs., makes 12 fl. oz.
2-10.
It is important to note that excessive caffeine intake is categorized at 500-600mg per day (3). Excessive intake can start to generate a tolerance, an addiction, and side effects. The average adult in the United States consumes about 300mg per day, which is just under 1 Starbucks grande coffee provides, or two Dunking Doughnuts cappuccino (1).
Of course, when we talk about the average person, there are some people who don’t consume any, and others who go overboard. If you get a Latté at a coffee shop on your way to work, then serve yourself 1-2 cups of coffee while at the office, you may easily fall into the category of people who go overboard with their caffeine consumption, with 500-800mg of caffeine per day.
Notice that even decaf coffees aren’t completely free of caffeine. They have anywhere between 2 and 25 mg of caffeine.
If you take any drugs throughout the day or if you drink tea as well, these all add to your caffeine consumption.
Let’s take a look at other products that contain caffeine.
Teas, Medicines, and Other Caffeinated Products
Unless teas are herbal, they contain caffeine. In many cases, the concentration isn’t as high as for coffee, but it is still significant for many, especially if you are a tea guzzler.
Table 2: Caffeine in Teas
Teas
Serving Size
Caffeine (mg)
Starbucks Tazo Awake—Brewed Tea or Tea Latte
grande, 16 fl. oz.
135
Starbucks Tazo Earl Grey—Brewed Tea or Tea Latte
grande, 16 fl. oz.
115
Starbucks Tazo Chai Tea Latte
grande, 16 fl. oz.
95
Starbucks Tazo Green Tea Latte—Iced or regular
grande, 16 fl. oz.
80
Black tea, brewed for 3 minutes
8 fl. oz.
30-80
Snapple Lemon Tea
16 fl. oz.
62
Lipton Pure Leaf Iced Tea
18.5 fl. oz.
60
Green tea, brewed for 3 minutes
8 fl. oz.
35-60
Lipton 100% Natural Lemon Iced Tea, bottle
20 fl. oz.
35
Arizona Iced Tea, black, all varieties
16 fl. oz.
30
Nestea Unsweetened Iced Tea Mix
2 tsp., makes 8 fl. oz.
20-30
Arizona Iced Tea, green, all varieties
16 fl. oz.
15
Lipton Decaffeinated Tea—black or green, brewed
8 fl. oz.
5
Herbal Tea, brewed
8 fl. oz.
0
Of course, naturally brewed teas have many natural and therapeutic benefits (varying depending on the type of leaf), including providing powerful antioxidants and boosting metabolism.
When we are talking about monitoring caffeine consumption, however, it is important to take into account how many milligrams each cup provides, especially if you are particularly sensitive to caffeine.
The teas with the highest caffeine content tend to be Earl Grey, Green Tea, Black Tea, and Chai Tea (which is made with a black tea). Of course, the concentration of caffeine depends on the brewing time. Longer brewing times result in higher caffeine concentrations.
Don’t be fooled by powdered tea mixes or bottled varieties; they still provide important amounts of caffeine.
If you would like to still take advantage of some of the therapeutic benefits of tea, or want to warm up on a cold day, without increasing your caffeine intake significantly, go for the herbal varieties instead. Herbal brewed teas do not provide any caffeine.
Of course, we can’t forget to talk about sodas/soft drinks and energy drinks when talking about beverages with caffeine. This is important to talk about because it is a source of caffeine for children and young adults that do not drink coffee. Especially with the rise of energy drink consumption, it is important to inform yourself, since the effects of caffeine on the brains of children and young adults is the same or intensified, and they, too, can build up a tolerance and an addiction.
Note that the below table notes the serving size, but in many cases the bottle or can has more than one serving. In parentheses is the amount of caffeine in the bottle. Also, in the first line of the table, you will see the FDA’s official limit for caffeine in colas.
Table 3: Caffeine in Soft Drinks
Soft Drinks
Serving Size
Caffeine (mg)
FDA official limit for cola and pepper soft drinks
12 oz.
71 (200 parts per million)
Pepsi MAX
12 oz.
69
Mountain Zevia (Zevia)
12 oz.
55
Mountain Dew, regular or diet
12 oz.
54 (20 oz. = 90)
Diet Coke
12 oz.
47 (20 oz. = 78)
Dr Pepper or Sunkist, regular or diet
12 oz.
41 (20 oz. = 68)
Pepsi
12 oz.
38 (20 oz. = 63)
Coca-Cola, Coke Zero, or Diet Pepsi
12 oz.
35 (20 oz. = 58)
Surge
8 oz.
35 mg (20 oz. = 87.5 mg)
Coca-Cola Life
12 oz.
27 mg (20 oz. = 45 mg )
Pepsi True
7.5 oz.
24 mg (20 oz. = 64 mg)
Barq’s Root Beer, regular
12 oz.
23 (20 oz. = 38)
7-Up, Fanta, Fresca, ginger ale, or Sprite
12 oz.
0
Root beer, most brands, or Barq’s Diet Root Beer
12 oz.
0
The first thing that stands out is how Pepsi Max literally has the maximum amount of caffeine allowed per serving. Coca Cola has almost half of that, with 35 mg per serving, if drinking only 12 ounces. If a 20 oz bottle is purchased, however, the amount of caffeine increases to 58 milligrams.
People tend to associate “clear” soft drinks like Sprite and 7-Up with having no caffeine. In most cases, this is true. However, there are a few tricksters. Mountain Dew, for example, has one of the highest amounts of caffeine per serving, and for a 20-oz bottle, it passes the allowed amount of caffeine.
Now let’s look at the dangerous drinks: the energy drinks.
Table 4: Energy Drinks
Energy Drinks
Serving Size
Caffeine (mg)
Bang Energy Drink
16 fl. oz.
357
Redline Energy Drink
8 fl. oz.
316
Rockstar Citrus Punched
16 fl. oz.
240
5-hour Energy
1.9 fl. oz.
208
Full Throttle (Monster)
16 fl. oz.
200
Frava Caffeinated Juice
16 oz.
200
Monster Energy
16 fl. oz.
160
Rockstar
16 fl. oz.
160
Venom Energy Drink (Dr Pepper/Seven Up Inc.)
16 fl. oz.
160
NOS Energy Drink (Monster)
16 fl. oz.
160
AMP Energy Boost Original (PepsiCo)
16 fl. oz.
142
NoDoz Energy Shots
1.89 fl. oz.
115
Mountain Dew Kick Start
16 fl. oz.
92
ávitāe Caffeinated Water
16.9 oz.
90
Red Bull
8.4 fl. oz.
80
V8 V-Fusion+Energy
8 fl. oz.
80
Ocean Spray Cran-Energy
20 fl. oz.
55
Glacéau Vitaminwater Energy
20 fl. oz.
50
Starbucks Refreshers
12 fl. oz.
50
Many of these drinks have significantly more caffeine than coffee, and the top two have more than the average adult in the use consumes. Keep in mind that in addition to caffeine, energy drinks tend to have other substances like high sugar content. They also have ingredients such as ephedrine, taurine, and ginseng, all of which stimulate the body in different ways, and some of which are concerning to heart health (5).
Of course, we can’t leave drugs and supplements out of the analysis.
Table 5: Over-the-Counter Pills
Over-The-Counter Pills
Serving Size
Caffeine (mg)
Zantrex-3 weight-loss supplement
2 capsules
300
NoDoz or Vivarin
1 caplet
200
Excedrin Migraine
2 tablets
130
Midol Complete
2 caplets
120
Bayer Back & Body
2 caplets
65
Anacin
2 tablets
64
As we can see above, some weight-loss supplements want increase energy expenditure by adding caffeine, which can help make you more active.
Be careful when taking these pills at night, as they can interrupt sleep or cause insomnia.
Can you Overdose on Caffeine?
Caffeine is usually completely removed from the brain relatively quickly. In general, it doesn’t tend to affect higher brain functions or concentration. However, if you consume too much caffeine, whether through coffee, tea, or other products, you may develop a tolerance to it (3).
Caffeine is considered a drug, and it is possible to overdose on caffeine. For most people, the upper limit is 500-600mg for adults, but some people may be more sensitive or more tolerant.
The effects of a caffeine overdose can be dangerous, and may even lead to death.
Some of the symptoms of caffeine overdose include:
Breathing trouble
Changes in alertness
Confusion
Convulsions
Diarrhea
Dizziness
Fever
Hallucinations
Increased thirst
Increased urination
Irregular heartbeat
Muscle twitching
Rapid heartbeat
Sleeping trouble
Vomiting (6)
Overdose in babies is particularly dangerous. Some of the symptoms may include:
Muscles that are very tense, then very relaxed
Nausea
Rapid, deep breathing
Rapid heartbeat
Shock
Tremors
Vomiting (6)
If someone is suspected of having a caffeine overdose, is important NOT to make this person vomit, unless told to by a doctor or by poison control.
If you or someone you know is suspected of suffering from caffeine overdose, it is important to call the US National Poison Control Center (1-800-222-1222).
Overdose must be treated in the hospital, and it is treated as a poisoning. The person affected may be given an IV, activated charcoal, provided breathing support and heart tracing. In some cases the person might have to be intubated in order to wash how the stomach.
The person might be subjected to a few days in the hospital, but in extreme cases, death may result from convulsions or irregular heartbeat (6).
Caffeine and Addiction
It is possible to be addicted to caffeine, but most people don’t know it because they continue to consume coffee regularly.
Caffeine addiction becomes evident when the person tries to quit. They may experience caffeine withdrawal (or coffee withdrawal).
According to the University of Michigan, some of the most common effects of caffeine withdrawal include:
Headaches (often known as caffeine headaches)
Irritability
Nervousness
Nausea
Constipation
Muscular tension
Many of these symptoms start to appear about 12-24 hours after a person stops consuming caffeine, and they disappear anywhere between a few days to a week. As this can be very uncomfortable, it is recommended that you gradually decrease caffeine intake over time in order to avoid experiencing intense withdrawal symptoms (7).
Are There Any Benefits to Drinking Caffeine?
Some scientific studies have shed light on a range of potentially positive effects of moderate caffeine consumption on our health. Some of these potential benefits include:
Reducing the risk of liver, mouth and throat cancer (8,9)
Have positive effects on the brain
Reducing suicide risk
Boost long-term memory
Protection against type 2 diabetes, Parkinson’s disease, cardiovascular disease, and stroke (10)
Keep in mind that these benefits are related to a moderate consumption of caffeine. So keep your caffeine consumption to below 500-600mg per day.
Caffeine During Pregnancy
Women who are pregnant tend to experience a slower rate at which caffeine is broken down. This is particularly true during the later stages of pregnancy (3).
The University of Michigan states:
“Some studies show an association between high doses of caffeine and an increased rate of miscarriages, premature deliveries or low birth weights. However, complicating factors such as smoking and alcohol use were not accounted for in these studies. In high doses, caffeine can affect fetal breathing and heart rate.
“If you are pregnant, or planning to become pregnant, consider your options (e.g. eliminating caffeine or limiting intake to 200-300 mg per day). Discuss these options with your clinician.” (7)
In general, it is recommended that caffeine intake is limited during pregnancy because of the potentially dangerous effects it can have. However, some studies show that lower doses have no effect. It is important to talk to your doctor about your options if you want to continue to consume caffeine during pregnancy.