Green Tea Caffeine vs Coffee: How Do They Compare?
Caffeine is the same compound whether it comes from coffee or green tea. The main difference is the amount. The FDA lists about 37 mg of caffeine in 12 oz of green tea and 113 to 247 mg in 12 oz of brewed coffee. Your total for the day matters more than the source.
How much caffeine is in each cup
Caffeine amounts vary with the plant, the brew and the size of the cup. Here are the figures from two government sources:
| Drink | Serving | Caffeine | Source |
|---|---|---|---|
| Green tea | 12 oz | About 37 mg | FDA |
| Brewed coffee | 12 oz | 113 to 247 mg | FDA |
| Coffee | 6 oz cup | 75 to 100 mg | MedlinePlus |
| Espresso | 1 oz | 40 mg | MedlinePlus |
| Black or green tea | 16 oz | 60 to 100 mg | MedlinePlus |
The FDA notes that the caffeine in specific products, and the size of the container, can vary a lot. A large coffee shop cup can hold far more than a small home mug. If a product lists its caffeine, that number is the one to trust.
Same caffeine, different package
MedlinePlus explains that caffeine occurs naturally in more than 60 plants. Coffee beans and tea leaves are two of them. Once it is in your body, caffeine from either source works the same way.
What differs is everything else in the cup. Green, black and oolong teas all come from the same plant, Camellia sinensis, according to the National Center for Complementary and Integrative Health (NCCIH). Green tea leaves are steamed or pan fried and dried without fermentation. Tea leaves also contain L-theanine, an amino acid. Coffee has its own mix of compounds, and usually a lot more caffeine per cup.
How caffeine works and how long it lasts
MedlinePlus says caffeine stimulates the central nervous system, which can make you feel more alert. It reaches its peak level in your blood within about an hour, and its effects can last four to six hours.
That timing matters for sleep. MedlinePlus advises avoiding caffeine, especially in the afternoon and evening, as part of healthy sleep habits. A cup at 4 p.m. can still be working at bedtime.
How much is too much
For healthy adults, the FDA has cited 400 mg of caffeine a day as an amount not generally linked to negative effects. That is about two to three 12 oz cups of coffee. MedlinePlus agrees that, for most people, up to 400 mg a day is not harmful.
Too much caffeine can cause restlessness, shakiness, trouble sleeping, headaches, dizziness and a fast heartbeat. People also vary. Some feel jittery after one cup, while others feel little change.
Is green tea safe?
NCCIH says no safety concerns have been reported for green tea consumed as a drink by adults. It does still contain caffeine, so it counts toward your daily total.
Green tea extracts are a different story. NCCIH notes that liver problems have occurred in a small number of people, mainly with green tea extract taken in tablets or capsules. Green tea in large amounts may also lower blood levels of nadolol, a heart medicine, and the extract may affect atorvastatin, a cholesterol medicine. If you take any medicine, ask your doctor before using green tea products beyond a normal cup of tea.
Choosing for your day
- For a gentle lift, a cup of green tea has much less caffeine than most coffee.
- For a stronger cup, brewed coffee usually has several times more.
- For a set amount, a product with caffeine listed on the label lets you count exactly what you are getting.
- For the afternoon, choose less caffeine, or none, so it does not reach into your evening.
Whatever you choose, it works best on top of the basics: water, a steady sleep schedule, regular meals and daylight.
Where EnerZen fits
EnerZen is our energy drink mix made with natural caffeine from green tea. A full serving of two scoops (7 g) has 200 mg of caffeine, 100 mg of L-theanine and 1,000 mg of taurine. It also has seven B vitamins, plus magnesium, sodium and potassium, with 20 calories and no sugar. Mix one scoop with 6 to 10 oz of water, or two scoops with 12 to 20 oz.
One full serving of EnerZen has about as much caffeine as a 12 oz brewed coffee, and much more than a cup of green tea. One scoop gives you half that, 100 mg. EnerZen comes in six flavors, all with the same formula, in our Energy collection. Nuvazen products are made in FDA-registered, GMP-compliant facilities, with a Certificate of Analysis (COA) for every product.
Who should check with a doctor first
- Pregnancy and breastfeeding. MedlinePlus advises keeping caffeine under 200 mg a day during pregnancy. Caffeine also passes into breast milk. Talk to your provider about your limit.
- Children and teens. The FDA says medical experts advise against energy drinks for children and teens. EnerZen's label says to keep it out of reach of children.
- Health conditions. MedlinePlus suggests checking with your provider if you have heart rhythm problems, high blood pressure, acid reflux or ulcers, frequent headaches or trouble sleeping.
- Medicines. Some medicines interact with caffeine or green tea. EnerZen's label says to consult your physician first if you take any medication.
Related reading: Is 200 mg of Caffeine a Lot? How It Compares
Frequently asked questions
Does green tea have less caffeine than coffee?
Usually, yes. The FDA lists about 37 mg in 12 oz of green tea and 113 to 247 mg in 12 oz of brewed coffee. Amounts vary by brand, brew and cup size.
Is caffeine from green tea different from coffee caffeine?
No. The caffeine is the same. The drinks differ in how much caffeine they have and in the other compounds that come with it, such as L-theanine in tea.
Can I have EnerZen and coffee on the same day?
Add up your caffeine first. A full serving of EnerZen has 200 mg. A 12 oz brewed coffee can have 113 to 247 mg. Together, that can reach the 400 mg the FDA cites for healthy adults.
How late in the day can I have caffeine?
MedlinePlus says caffeine's effects can last four to six hours, and advises avoiding it in the afternoon and evening for better sleep. A simple habit is to have your last caffeinated drink by early afternoon. If caffeine is part of your work day, A Simple Deep Work Routine for Busy Days shows where it fits.
Sources: FDA, Spilling the Beans: How Much Caffeine Is Too Much?; MedlinePlus, Caffeine; MedlinePlus, Caffeine in the diet; MedlinePlus, Healthy Sleep; NCCIH, Green Tea.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
