Here's the L-Theanine in Your Green Tea – And What Trials Used

About 10 milligrams. That’s the L-theanine in a cup of steeped green tea, according to Saratoga Tea & Honey. News-Medical says “most clinical studies use 200 mg or more daily in supplement form”. Divide 200 by 10, and plain green tea needs 20 cups a day to match.

L-Theanine Is an Amino Acid Found Mostly in Tea Leaves

Cleveland Clinic describes L-theanine as a non-essential, non-protein amino acid. It’s found mostly in tea leaves, green and black alike, and in some mushrooms. Non-essential means you don’t need it from food. Non-protein means the body doesn’t use it to build protein.

The tea leaves in question come from Camellia sinensis, the plant that both green and black tea are made from.

Matching a 200 mg Trial Dose Takes About 7 to 25 Cups or 5 to 10 Matcha Portions

Bigelow cites a 2016 study in the journal Nutrients that used 200 mg a day. Bigelow calls that “roughly the amount in eight cups of tea.” That line assumes about 25 mg a cup (200 ÷ 8 = 25), which is 2.5 times Saratoga’s figure for plain steeped green tea.

The table below measures every tea against the same 200 mg target. “—” means not listed. The milligram figures are estimates from sellers and publishers, not lab results for any one package. Artful Tea describes Gyokuro and Kabusecha as high in L-theanine but gives no milligram figure, so they sit outside the table.

Tea (source)	L-theanine per serving	Caffeine per serving	Servings to match 200 mg	Vs. steeped green tea
Steeped green tea (Saratoga)	~10 mg	—	200 ÷ 10 = 20 cups	1x (baseline)
Green tea, 250 mL cup (News-Medical)	8-30 mg	—	200 ÷ 30 = 6.67 to 200 ÷ 8 = 25 cups	8 ÷ 10 = 0.8x to 30 ÷ 10 = 3x
Matcha (Saratoga)	20-40 mg per portion (portion size not stated)	—	200 ÷ 40 = 5 to 200 ÷ 20 = 10 portions	20 ÷ 10 = 2x to 40 ÷ 10 = 4x
Bigelow Peak Energy Black Tea (Bigelow)	25 mg added per 8 oz	75 mg	200 ÷ 25 = 8 cups (added L-theanine only)	25 ÷ 10 = 2.5x
Bigelow Whispering Wildflowers Herbal Tea (Bigelow)	25 mg added per 8 oz	0 mg	200 ÷ 25 = 8 cups	25 ÷ 10 = 2.5x

Here is how to read the last column. One fortified Bigelow cup adds what 2.5 cups of steeped green tea carry. By Saratoga’s figures, matcha carries 2 to 4 times as much as steeped green tea.

News-Medical’s range is 3.75 times wide (30 ÷ 8), so the plain-tea count swings from about 7 cups to 25. An 8 oz cup is about 237 mL, close to News-Medical’s 250 mL cup, so the rows compare fairly.

Shade-Grown Gyokuro and Kabusecha Spend Two to Three Weeks Under Cover

What sets these two green teas apart is shade before harvest. Artful Tea says Gyokuro is shade grown for up to three weeks before it’s picked. Kabusecha gets a shorter stretch, typically about two weeks.

Artful Tea describes both as high in L-theanine. On a tea label, either name tells you the leaf was shaded. The length of the shading is what separates the two.

Eight Fortified Cups Bring 600 mg or 0 mg of Caffeine

Bigelow’s two fortified teas carry the same 25 mg of added L-theanine per 8 oz cup, per Bigelow. Their caffeine is not the same. Peak Energy Black Tea lists 75 mg a cup, and Whispering Wildflowers Herbal Tea lists 0 mg.

Eight cups of Peak Energy supply 200 mg of added L-theanine (8 x 25 mg). Bigelow says its black teas also contain L-theanine naturally but lists no figure for that part. Those 8 cups bring 8 x 75 mg = 600 mg of caffeine with them. Eight cups of Whispering Wildflowers bring 200 mg of added L-theanine and no caffeine.

Removing the caffeine doesn’t remove the L-theanine. Harney & Sons says decaffeinated teas made from Camellia sinensis still contain it.

A 2025 Review Finds the Evidence for Many Claims Limited

A review on ScienceDirect asks whether the science on L-theanine matches the hype. It concludes: “The evidence supporting many popular health claims remains limited.”

News-Medical reports a narrower result in healthy volunteers: a single 200 mg dose of L-theanine “significantly reduces salivary cortisol levels and sympathetic arousal in response to cognitive stress.” Salivary cortisol is a stress hormone measured in saliva. Sympathetic arousal is the body’s fight-or-flight response.

The evidence is thin. One review calls it limited, and the clearest finding cited here comes from one 200 mg dose in healthy volunteers. By Saratoga’s figure, that dose equals about 20 cups of steeped green tea. More ingredient evidence reviews use the same trial-dose method.

Fortified Tea Gives One Fixed Number, Plain Leaf Gives a Range

If you want one fixed amount per cup, a fortified tea gives a single number: 25 mg per 8 oz for both Bigelow blends. Plain leaf gives a range: steeped green tea near 10 mg, 8-30 mg per 250 mL cup by News-Medical’s figure, and matcha at 20-40 mg.

If you prefer plain leaf, Gyokuro and Kabusecha are the shaded teas Artful Tea describes as high in L-theanine. For green tea, Bigelow’s brewing advice is water just below boiling.

Verdict: Tea Gives Tens of Milligrams; Trials Used 200 mg Supplements

Verdict: Green tea gives L-theanine in the tens of milligrams per cup. Matching the 200 mg daily dose most clinical studies used takes about 7 to 25 cups of green tea or 5 to 10 matcha portions, depending on the tea.

The flaw, and its fix: The amount in plain tea is an estimate with a wide range, 8-30 mg per 250 mL cup according to News-Medical. The fix is a product that states its milligrams. Bigelow’s fortified teas list 25 mg per 8 oz, and the trials News-Medical describes used supplements, whose labels give milligrams per serving.

Strengths: Decaf Camellia sinensis tea keeps its L-theanine, per Harney & Sons. Whispering Wildflowers pairs 25 mg of L-theanine with 0 mg of caffeine.

Who should skip Peak Energy: Anyone limiting caffeine, since 8 cups bring 600 mg. Whispering Wildflowers gives the same 25 mg per cup with no caffeine.

Next step: Small nootropic pouches sold with caffeine and L-theanine get the same per-serving check in nootropic pouches label math for caffeine and L-theanine per pouch.

Next step: read more in Ingredient evidence on FocusIQ.

FAQ: L-Theanine and Green Tea

Does Matcha Have More L-Theanine Than Steeped Green Tea?

Yes. Matcha is powdered shade-grown green tea, per Artful Tea, and Artful Tea says shading raises the plant’s L-theanine and its caffeine. Saratoga notes matcha is “consumed as a powder rather than an infusion,” so you drink the leaf itself.

Does Black Tea Contain L-Theanine?

Yes. Cleveland Clinic names black tea alongside green tea as a tea-leaf source. Bigelow’s Peak Energy Black Tea also has 25 mg of added L-theanine per 8 oz cup.

Can an Herbal Tea Contain L-Theanine?

Not naturally. Herbal teas aren’t made from Camellia sinensis, so they don’t contain L-theanine, per Artful Tea, and Bigelow says it “is not naturally present in herbal tea.” Whispering Wildflowers is an herbal tea with 25 mg of L-theanine added per 8 oz cup, per Bigelow.

Who Should Check With a Clinician First

The NIH Office of Dietary Supplements’ consumer guide, Dietary Supplements: What You Need to Know, notes that supplements can contain amino acids, the class L-theanine belongs to. Its general cautions point to a talk with a doctor or pharmacist first if any of these apply:

• you take prescription medicines, since the guide says supplements “can also interact with some medicines”
• you are pregnant or nursing
• you plan to give a supplement to a child

The same guide says makers add supplement ingredients to beverages, so you “may get more of these ingredients than you think.” Bring the product label so the milligrams of L-theanine and caffeine per serving are in front of you both.

This article summarizes published sources for general information. It is not medical advice and does not promise any result.