Astill and colleagues (2001, Journal of Agricultural and Food Chemistry) ran a comprehensive study at Unilever Research, mapping how each compound class extracts from black and green tea leaves over time. The kinetics they documented are consistent with established tea extraction chemistry.

Caffeine extracts fast. Most of the caffeine in the leaf is in your cup within the first 1-2 minutes of steeping. By 3 minutes, caffeine extraction is essentially complete and additional brew time adds little.

Catechins extract slower. EGCG, EGC, ECG, and EC, the polyphenols that drive most of the health-related research on green tea, are larger molecules with more complex extraction kinetics. They continue extracting meaningfully through 3-5 minutes. A 1-minute brew captures only a fraction of the catechin content the same leaf could deliver.

Tannins extract last. The high-molecular-weight polymeric polyphenols that produce astringency and harsh bitterness become prominent later in the brew. After roughly 4-5 minutes of steeping, the tannin fraction rises notably and the cup turns from bright to harsh.

A separate effect that applies regardless of brew time: tea polyphenols as a class bind non-heme iron. Hurrell and colleagues (1999, British Journal of Nutrition) reported that drinking tea with a meal reduced non-heme iron absorption by approximately 60 percent in healthy subjects. This effect is not specific to over-steeped tea. Even normally brewed tea consumed with iron-containing food has the same effect, because all the major tea polyphenols (catechins included) participate in iron binding.

What this means in practice. The tea bag dipped for 30 seconds and pulled out is mostly a caffeine delivery vehicle with minimal catechin content. The tea steeped for 8 minutes is a tannin-heavy infusion that tastes harsh. The 3 to 5 minute window captures the catechin peak before the astringent tannin fraction builds substantially.

Two caveats worth noting. The exact extraction kinetics depend on water temperature, leaf grade, and whether the tea is loose-leaf or in a bag. Higher temperatures accelerate all extraction. Smaller particle sizes (commercial tea bag dust) extract faster than whole leaves. The 3 to 5 minute window applies to typical brewing conditions: roughly 95 degrees Celsius water, standard tea bag, one cup volume. Green tea is often brewed at lower temperatures (75-85 degrees Celsius) which slows catechin extraction and extends the optimal window. The Astill 2001 study was conducted at Unilever, the parent company of Lipton, which is relevant context. The underlying kinetics are not industry-disputed and align with established food chemistry.

A practical implication. If you are drinking tea for the catechin and EGCG content that drives most of its associated health research, the 30-second tea bag dunk delivers roughly the same caffeine as a longer brew but only a fraction of the catechins. If you are drinking tea purely for caffeine, a short brew is fine. If you have iron status concerns and consume tea with meals, the binding effect happens regardless of brew time. Drinking tea between meals rather than with them is the relevant lever for iron absorption, not brew time.

Same leaf. Same water. Three minutes of difference changes the chemistry of what you are drinking.

Astill et al., Journal of Agricultural and Food Chemistry, 2001 Hurrell et al., British Journal of Nutrition, 1999