Caffeine is the most widely consumed psychoactive substance in the world, found in about 60 different plants. Globally, it is most often consumed through tea and coffee. Its main effect is stimulating the nervous system, but it leaves the body relatively quickly and does not accumulate.

Why Tea and Coffee Feel Different.

Many people notice that the stimulating effect of tea feels gentler than that of coffee. This is because tea also contains L-theanine, an amino acid that works in synergy with caffeine. Together they promote alertness and concentration, while at the same time reducing jitters, supporting a calm state of mind, and enhancing overall mood.

How Much Caffeine Is in a Cup of Tea?

For a healthy adult, the recommended daily intake of caffeine is up to about 400 mg.

A standard cup of tea (250 ml) may contain anywhere from 10–60 mg of caffeine. The variation is wide because caffeine levels depend on many factors — from the type of leaves to how the tea is brewed.

Key factors that influence caffeine in tea

1. Leaf buds vs. mature leaves

Young tea buds contain more caffeine than older, larger leaves. This is because the Camellia sinensis plant produces caffeine as a natural insect repellent. Tender buds are more vulnerable to pests, so the plant protects them with higher caffeine content.

Season also matters: summer harvests tend to have more caffeine than spring harvests, again due to greater insect activity.

2. Tea variety

Camellia sinensis has several varieties and hybrids, but two are most common in tea production:

• Camellia sinensis var. sinensis

• Camellia sinensis var. assamica

Assamica leaves can contain up to 30% more caffeine than sinensis. This variety is most often used for black teas, grown widely in southern China, India, Africa, and Sri Lanka. The “regular black tea” sold in most supermarkets usually comes from assamica grown in India or Sri Lanka.

3. Brewing method

How you prepare your tea also makes a big difference. Hotter water extracts more caffeine, as do longer steeping times and larger amounts of leaf. For example, tea brewed with boiling water will contain more caffeine than tea made with slightly cooler water

Final thoughts

By keeping these factors in mind, you can adjust your brewing to control how much caffeine ends up in your cup.

If you’re sensitive to caffeine, a spring-harvested oolong tea from China may be a gentler choice — these teas are usually made from larger leaves, which naturally contain less caffeine.