Contrary to popular belief, all teas contain caffeine — including green tea and white tea. The only types of tea with no caffeine are the herbal teas, which are not derived from true tea plant leaves (Camellia sinensis).
Many people relish drinking tea throughout the day. Others who are caffeine sensitive switch to decaffeinated teas starting in the afternoon. You can buy decaffeinated tea, but I have read from many sources that much of the caffeine diffuses from the tea leaves after about 45 seconds of steeping. Throwing this initial brew away and re-steeping the tea with fresh, hot water supposedly leaves a very-low caffeine tea.
I have never seen actual numbers quantifying the caffeine reduction and wondered if this advice was really true. It seems that others have had the same question and a group of food scientists from Auburn University measured the caffeine levels in tea versus the amount of time spent steeping for several different types of tea.
Their results? Quite interesting…
They verified that the caffeine levels of tea are reduced by pouring out the first brew, just not as much as you would expect. Their experiment showed that after 5 minutes, the caffeine content was reduced between 61% to 76%, depending on the type of tea. In general, bagged tea released its caffeine more quickly than loose leaf tea.
I wish they had measured the caffeine reduction per second so I could know for sure how much the caffeine is reduced for a 45-second steep (unfortunately the experimental method of measuring caffeine in foods requires expensive, specialized equipment).
However, the paper presents data for the caffeine dispersal in 5 minute intervals. Plus, we know that at time = 0 seconds, there is no caffeine dispersal. Therefore, I extrapolated the following curve and calculated the caffeine reduction at 45 seconds to be a mere 17%!
The red dots in the above plot show the data from the published study and the green dot is my extrapolated estimate. Using my data fit, I estimated a few more data points:
| Diffusion Time |
Caffeine Reduction |
| 15 secs |
6% |
| 20 secs |
7% |
| 30 secs |
11% |
| 45 secs |
17% |
| 60 secs |
21% |
| 90 secs |
30% |
In case you want to calculate the caffeine reduction yourself, here is the formula I calculated (where t is in minutes, so you would use t=0.75 to calculate the dispersal in 45 seconds):
100-100.214*Exp[-0.242611*t]
Considering that the caffeine reduction in 45 seconds is so low and that almost all the taste has certainly leached away by that point, the best bet is to just go with store-bought decaffeinated tea!
References:
Monique B. Hicks, Y-H.Peggy Hsieh , Leonard N. Bell, Tea preparation and its influence on methylxanthine concentration, Food Research International, Volume 29, Issues 3-4, April-May 1996, Pages 325-330
