Understandably, many tea drinkers are concerned with the amount of caffeine in their cup. While some of us rely on a dose of caffeine to get moving in the morning, others need to limit their intake for a good night’s rest. Either way, estimates of caffeine level based on broad tea categories may seem both logical and convenient. As with flavor, we are psychologically predisposed to associate caffeine levels with a visual cue like color.

Unfortunately, the basis for these estimates is flawed. Despite the wide range of colors, aromas, and flavors, all tea leaves have their origins in the same species, and caffeine content remains relatively stable throughout the crafting process. Therefore, black tea does not have the most caffeine, nor does white tea have the least. Many studies, like this one from the USDA, have shown that caffeine levels vary more between individual teas within a single type than between the familiar color-coded categories. Even such scientific research on the topic is contradictory and inconclusive, proving that the only way to know exactly how much caffeine is in a tea leaf is to test it in a lab.

Despite the general confusion, a few variables are widely accepted as influences on the ultimate caffeine level. These are:

The variety of the Camellia sinensis plant being used.

Thousands of varieties of the tea plant are grown throughout China and throughout the world, each with it’s own set of genetic specifications. Just as varieties of grapes have different levels of sugar, varieties of tea leaves can have different levels of caffeine. A single variety of Camellia sinensis could potentially be crafted into a tea of any category, and would have the same level of caffeine whether it became a green tea or a black tea.

The growing conditions of the plant.

Caffeine is produced by the tea plant as a natural defense against insects, and therefore the quantity of caffeine increases in growing conditions with high pest threats. Mass-produced teas grown in hot lowland regions will have more caffeine to deter those pests. However, caffeine is also known to taste bitter on the human palate, so extracting the maximum caffeine from these leaves usually results in an unpleasant cup.

The age of the leaves when they are harvested.

It’s generally accepted that spring buds and mature leaves have different levels of caffeine, and often assumed that the budding leaves have more, since they are the most appetizing to threatening pests and thus require more robust defenses. But research comparing teas of different harvests is inconclusive, indicating that caffeine levels are usually more affected by variety and growing conditions than the age of the leaf.

In the end, even well-informed vendors are unlikely to have the exact details on caffeine content. To add to the confusion, caffeine affects each person differently, and the rate at which it is metabolized in the body can be affected by genetics, gender, and other variables.

Luckily, the process of brewing tea offers the opportunity for complete control over how much caffeine is extracted from the leaf. Steeping your tea with fewer leaves, cooler water, or for a shorter period of time is the most reliable way to reduce the amount of caffeine in your cup. Try adding more leaf, using hotter water, or steeping longer to extract more.

Additionally, brewing whole leaves can offer more control, since they present less exposed surface area and therefore release their compounds more gradually than broken or chopped leaves. Though an initial rinse or one-minute steep will not fully decaffeinate a tea, as is sometimes claimed, caffeine does decrease over the course of several infusions.

No matter what your preference, we recommend customizing your cup, rather than depending on misleading generalizations. By experimenting with brewing methods and tasting new teas, you’re sure to find an infusion with the right amount of caffeine for you.

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