L-Theanine and Tea Leaves: A Plain-English Explainer Guide

What Is an Amino Acid?

Amino acids are small molecules that living things use as building blocks. Most people first hear about them in connection with protein, since proteins are made of long chains of amino acids. Plants, animals and microbes all make and use them, and there are many different kinds found in nature.

The "L" in L-theanine refers to a particular three-dimensional form of the molecule. Chemists use the L and D labels to tell apart two mirror-image versions of the same molecule, a bit like left and right hands. You will see the "L" form on many ingredient lists, because it is the form found in nature in most amino acids.

Theanine itself is a bit unusual because it is not one of the amino acids that go into building proteins. It is known as a naturally occurring amino acid in tea leaves, and that is the part of the story we will focus on in this plain-English explainer.

Meet the Tea Plant

All true tea comes from one species, Camellia sinensis, an evergreen shrub in the same genus as the ornamental camellias that bloom in many gardens. In cultivation, tea bushes are pruned to waist height so pickers can easily reach the tender young shoots at the top, usually the bud and the first couple of leaves.

The plant is native to parts of East and South Asia, and today it is grown in many countries with warm, humid climates and plenty of rain. Hillsides and mountain slopes are popular for tea, partly because they drain well and partly because cooler air at elevation slows leaf growth.

Harvest timing is part of the craft. In many regions the first picking of the year, called the first flush, happens in spring when new growth appears, and later pickings follow through the warm months. Skilled pickers choose shoots by hand for fine teas, while machines handle larger plantations that produce teas for everyday bags.

Tea has a long cultural history, and tea gardens are some of the most picturesque farmland in the world, with neat rows that follow the contours of the hills.

How Tea Is Grown and Processed

Some teas are grown in full sun, while others are shaded for a period before harvest. Shade growing is a traditional technique used for Japanese teas such as gyokuro and matcha, where bushes are covered for a number of days or weeks before picking. Producers use the method to shape the look and flavor of the finished leaf.

What surprises many people is that white, green, oolong and black teas all come from the same plant. The differences come from what happens after picking. Here is a simple map of the usual steps:

• Withering: freshly picked leaves are spread out so they soften and lose some moisture.
• Rolling or shaping: leaves are rolled, twisted or pressed, which breaks the surface and shapes the final look.
• Oxidation: leaves are exposed to air, which turns them darker. Black tea is fully oxidized, oolong is partly oxidized, and green and white teas are oxidized very little or not at all.
• Firing or drying: heat stops the process and dries the leaves so they keep well.

Quality and style depend on timing and temperature at each stage, so tea making is partly science and partly experience. Producers watch the color, aroma and feel of the leaves and decide when to move on to the next step. A tea maker who has done this for decades can often tell by touch when the leaves are ready.

Each step can be adjusted by the tea maker, which is why two teas from the same bush can taste so different.

Brewing Tips for a Better Cup

A few easy habits make a noticeable difference at home. Start with fresh, cold water, since stale or heavily flavored water shows up in the cup. Tea makers commonly suggest cooler water for delicate green and white teas, often a little below boiling, and water at or near a full boil for black tea.

Steeping time matters as well. Many people brew green tea for a couple of minutes and black tea for three to five, then adjust to taste. Over-steeping tends to make a cup taste bitter, so a timer is a handy kitchen friend.

• Measure your leaves instead of guessing; a small kitchen spoon works fine.
• Warm your cup or teapot with hot water first.
• Remove the leaves when the time is up.
• Store loose leaves in an airtight tin away from light, heat and strong smells.

Loose-leaf tea and tea bags both work. Loose leaves have room to unfurl, which many tea fans like, while bags are quick and tidy. Either way, the same plant sits at the start of the story, and the same basic habits apply: good water, a sensible steep time and fresh storage.

For more daily habit ideas, our guide to simple ways to drink more water pairs nicely with a cup of tea.

Reading L-Theanine on a Label

When you see L-theanine on an ingredient list, it names a specific compound. Reading labels is a skill that gets easier with practice, and the NIH Office of Dietary Supplements consumer guide is a friendly starting point. The FDA dietary supplements page provides more general background about how these products are labeled.

Nervelin is a dietary supplement in vegetable capsule form, 30 capsules per bottle. The brand names six ingredients: Ashwagandha Root, Passionflower Extract, Magnesium Glycinate, L-Theanine, Rhodiola Rosea and a Vitamin B Complex. You can see how they are presented on the Nervelin ingredients page.

The brand's graphic says to take one capsule daily, and the best habit is to follow the directions on your bottle label.

Curious how the brand describes its formula? Visit the how Nervelin works page for a friendly overview.

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