Caffeine

The composition tables give 3.5 g of caffeine per 100 g of gyokuro leaf against 2.3 g for sencha. Measured as leaf, gyokuro carries more. Shading is the usual explanation offered, though the tables give figures rather than causes.

In the brewed liquor the gap widens to eightfold: 0.16 g per 100 mL for gyokuro against 0.02 g for sencha. That is not all content. The tables brew each tea to its own protocol — 10 g of gyokuro into 60 mL, 10 g of sencha into 430 mL. The gyokuro figure comes from a cup brewed into about a seventh as much water.

So the amount you actually take in depends on the product and on how strongly and how often you brew, not on the type alone.

Cold brewing does not take it to zero. Caffeine simply dissolves slowly at low temperature; given hours it still comes out. Cold brew tastes smooth and unaggressive, which is easily read as meaning there is nothing in it.

In the tables, bancha runs 0.01 g per 100 mL of liquor and hojicha 0.02 g, against gyokuro's 0.16 g. These are measured under different brewing protocols for each tea, so the gap is not the difference you would get brewing them the same way.

On the brewing side, cooler water, less time and less leaf all reduce it — though each also thins the savoriness, so it is a trade against flavor.

Hojicha tends to be lower in caffeine, but roasting is not the whole reason. Many products are made from mature leaves and stems to begin with, and that weighs at least as much.

So two teas both sold as hojicha can differ considerably depending on what was roasted. Where the packet says what the raw material was, it is worth reading.

Setting caffeine aside, the flavor pairings are clear enough. With food, the restrained teas sit better: genmaicha, hojicha, bancha. They reset the palate without competing with the dish.

Gyokuro and kabusecha are dense and want cool water and patience, so they show themselves better on their own than alongside a meal.

What to drink at what hour is not something this page decides: sensitivity to caffeine varies from person to person. If it matters to you, take the figures above as a reference point and judge by your own experience.

It gives no daily limit, and no figure for pregnancy. The Japanese agriculture ministry states that Japan has set no clear standard or reference intake, and issues advisories based on overseas information instead. Beyond that, no Acceptable Daily Intake has been established for caffeine either in Japan or internationally, because individual variation is too wide. There is no basis on which to publish a number.

For anything that depends on your own situation — a condition, a medication, pregnancy — ask a medical professional. What is here is general information drawn from published composition tables, not medical advice.