Does cold brew have less caffeine than hot coffee?
Short answerNot the way you think
Not the way you think. Cold brew tastes smoother and milder, so people assume it’s weaker. But in a 2017 lab test, cold brew made from coarse-ground coffee had substantially more caffeine than hot coffee made from the same coffee and the same amount of water, about a fifth to a quarter more. How strong your cup is depends on the recipe and on how much ice and milk go in.
What we’d do
Treat a big cold brew like a big coffee, or bigger, until you know how your shop makes it. For an 11pm bedtime, time a 16 oz cold brew like a 16 oz coffee, finished by about 11am. If you want a mild afternoon drink, a small one is the safer order.
If you remember three things
- Mild taste doesn’t mean less caffeine. The smoothness comes from other compounds.
- Same coffee, same water, more caffeine. Coarse cold brew beat hot coffee in a 2017 lab test.
- The recipe decides your dose. How much coffee went in, and how much ice and milk went on top, sets what’s in your cup.
Why people believe it
Cold water seems like it should pull less out of the coffee, and cold brew tastes gentler, with less bitterness. Coffee sellers describe it that way too. Dunkin’ has said that “cold brew is less acidic and naturally sweeter than regular coffee, so it can easily be consumed black”, a line the 2017 researchers quoted in their paper.
Cold brew is like soaking dried beans overnight instead of boiling them. Cold water works much more slowly, but given enough hours it gets to the same place or further.
What the study found
Cold brew against hot, same coffee
Four coffees, medium or dark roast, medium or coarse grind. Fuller and Rao, Thomas Jefferson University, Philadelphia, 2017
Cold brew was steeped at room temperature, 35 g of coffee in 350 mL of water, from a New York Times recipe. Hot coffee was made in a French press with the same ratio. With coarse grinds, cold brew had substantially more caffeine, 1,230 against 970 mg per liter for the medium roast and 990 against 840 for the dark.
With medium grinds cold brew was also higher, but by too little to be sure. One lab, four coffees.
The researchers also found that cold brew’s caffeine had almost finished extracting by 6 to 7 hours, not the 10 to 24 hours most recipes call for. And cold brew made from medium roast had more caffeine than cold brew from dark roast, which fits what roast does to caffeine.
Why it tastes milder
It isn’t the caffeine. In the 2017 study the two brews had similar pH. A follow-up by the same team in 2018 tested six light roast coffees and again found the pH of hot and cold brew about the same, 4.85 to 5.13. The hot brews had more titratable acids, a measure of total acid, and more antioxidant activity. The smoothness comes from what the cold water leaves behind, while the caffeine comes out anyway.
The best case for it
Cold brew as served can be weaker than the brew in the jar. The recipe in the study used 35 g of coffee in 350 mL of water, about 1 part coffee to 10 of water, and a cup that’s half ice and milk has about half the caffeine of the brew it was poured from.
A particular cold brew can easily have less caffeine than a particular hot coffee, and it can easily have more. Coffee-shop drinks swing a lot anyway. In a 2003 lab test, coffee-shop coffees ran from 58 to 259 mg a serving, and the same drink from the same shop measured 259 to 564 mg on six days in a row.
More detail: the numbers from the study
| Coffee | Cold brew | Hot coffee |
|---|---|---|
| Medium roast, medium grind | 1,180 mg per liter | 1,040 mg per liter |
| Medium roast, coarse grind | 1,230 mg per liter | 970 mg per liter |
| Dark roast, medium grind | 1,080 mg per liter | 1,060 mg per liter |
| Dark roast, coarse grind | 990 mg per liter | 840 mg per liter |
That’s after 24 hours of steeping. Both kinds were brewed at 35 g of coffee per 350 mL of water, so a cup that’s half ice and milk has about half of these amounts.
3 sources
- Fuller M, Rao NZ, The effect of time, roasting temperature, and grind size on caffeine and chlorogenic acid concentrations in cold brew coffee, Scientific Reports, 2017doi.org
- Rao NZ, Fuller M, Acidity and antioxidant activity of cold brew coffee, Scientific Reports, 2018doi.org
- McCusker RR, Goldberger BA, Cone EJ, Caffeine content of specialty coffees, Journal of Analytical Toxicology, 2003pubmed.ncbi.nlm.nih.gov
