L-Theanine 101: Uses, Side Effects, Interactions, and Who It’s For

What Is L-Theanine?

Myprotein AU describes L-theanine as an amino acid found primarily in tea (especially green and black tea). Myprotein also notes it is available in supplement form and is well known for its calming and relaxing effects.

Source: Myprotein AU

How L-Theanine Works in the Body

Detailed mechanism of action (specific neurotransmitter pathways, clinical mechanism explanations, or “how it works” at a biochemical level): Not specified on the source page.

What the allowed sources consistently describe is that L-theanine is associated with relaxation and is often discussed alongside caffeine, including the idea of supporting focus while reducing “jittery” feelings from caffeine (as described by Musashi and Naturecan in their product/guide context).

Sources: Musashi, Naturecan AU

Key Benefits: What the Evidence Says

Important: The points below reflect what the allowed sources state and how they describe the research or intended use. Where a detail isn’t provided on the source pages, it is marked “Not specified on the source page.”

1) Relaxation / calm

Myprotein AU describes L-theanine as well known for its calming and relaxing effects. Naturecan AU describes L-theanine as an amino acid that may promote relaxation without drowsiness (as stated on its pre-workout product page).

Sources: Myprotein AU, Naturecan AU

2) Focus / performance when paired with caffeine

Musashi states that combining caffeine + L-theanine can support enhanced alertness and reaction time without “jittery” side effects (as written in its training-goals guide). Naturecan AU also discusses caffeine and notes it can sometimes lead to jitteriness or anxiety on its own, while describing L-theanine in the same formula context.

Sources: Musashi, Naturecan AU

3) Stress-response support (product positioning)

Musashi’s REAPER Nervous System Stress Matrix product page states that theanine supports a healthy stress response in the body (as presented on the product page).

Source: Musashi (REAPER Nervous System Stress Matrix)

Who Might Benefit Most

• People seeking calm/relaxation support: Myprotein AU describes L-theanine as calming/relaxing; Naturecan AU describes relaxation without drowsiness (in product context).
• People who use caffeine and want “smoother” focus: Musashi discusses caffeine + theanine for alertness without “jittery” effects; Naturecan discusses caffeine’s potential for jitteriness/anxiety on its own (in product context).
• People browsing stress/sleep/mood supplement categories: Healthylife lists multiple L-theanine products within its stress/sleep/mood/energy category section.

Sources: Myprotein AU, Naturecan AU, Musashi, Healthylife

Recommended Dosage and How to Take It

Myprotein AU states the “optimum dosage” has not been determined and that dosages used in research have ranged from 100–500 mg.

Best practice: Follow the label directions on the exact product you purchase, particularly if it is part of a multi-ingredient formula (for example, pre-workouts or stress-support blends).

Source: Myprotein AU

Best Time to Take L-Theanine (Timing and With/Without Food)

Specific timing guidance (morning vs evening, pre-workout vs bedtime) and with/without food rules: Not specified on the source page.

A practical approach supported by the way these products are discussed on allowed sources is to align timing to your goal:

• Relaxation-focused use: choose a time when you want a calmer feel (timing specifics not provided on the source pages).
• Focus + caffeine use: some brands discuss L-theanine in combination with caffeine in pre-workout or focus contexts.

Sources: Musashi, Naturecan AU

Forms and Quality: What to Look For on the Label

L-theanine appears as:

• Standalone L-theanine supplements: Healthylife lists multiple L-theanine products (capsules/tablets and powders) within its L-theanine category page.
• Multi-ingredient formulas: Naturecan includes L-theanine as one of the ingredients discussed on its pre-workout page; Musashi includes theanine in a “stress matrix” style product page.

What to check on the label:

• Amount per serve: Not specified on the source page (varies by brand/product).
• Whether caffeine is included: relevant for people sensitive to stimulants.
• Directions and “adults only” statements: Musashi’s REAPER product page includes an “ADULTS ONLY” direction statement and recommends taking capsules with food (as stated on the product page).
• Allergens/dietary suitability: Not specified on the source page (varies by product; check the ingredient list and claims on the exact item).

Sources: Healthylife, Naturecan AU, Musashi (REAPER)

Side Effects and Who Should Avoid It

Myprotein AU states that no adverse side effects have been found with L-theanine and references a study describing it as “safe and effective” (in the context discussed on that page).

Specific contraindications (who should avoid it), side effects in special populations, and long-term safety conclusions: Not specified on the source page.

If you are pregnant or breastfeeding, have a medical condition, or are taking medication, consult a clinician before starting L-theanine—especially if the product also contains caffeine or other active ingredients.

Source: Myprotein AU

Drug and Supplement Interactions

Specific drug interactions (named medicines/classes) and supplement interaction rules: Not specified on the source page.

The allowed sources frequently discuss L-theanine alongside caffeine. If your product contains caffeine (or you are combining L-theanine with caffeinated drinks), consider your stimulant sensitivity and total caffeine intake.

Sources: Musashi, Naturecan AU, Myprotein AU

FAQs

1) Is L-theanine found naturally in food?

Yes. Myprotein AU states L-theanine is found primarily in tea, especially green and black tea.

Source: Myprotein AU

2) How much L-theanine should I take?

Myprotein AU states the optimum dosage has not been determined and research dosages have ranged from 100–500 mg. Follow label directions for your chosen product.

Source: Myprotein AU

3) Can I combine L-theanine with caffeine?

Musashi discusses caffeine + theanine as a combination that can support alertness without “jittery” side effects (as written on its training-goals guide). Naturecan also discusses caffeine’s potential for jitteriness/anxiety when used alone, in the context of its pre-workout ingredients discussion.

Sources: Musashi, Naturecan AU

4) Does L-theanine cause drowsiness?

Naturecan AU describes L-theanine as potentially promoting relaxation without drowsiness (as stated on its pre-workout page). Broader clinical conclusions across all populations: Not specified on the source page.

Source: Naturecan AU

5) Are there known side effects?

Myprotein AU states no adverse side effects have been found with L-theanine and references a study describing it as safe and effective (in the context discussed on that page). Additional side effects: Not specified on the source page.

Source: Myprotein AU

Optional: Shop L-Theanine (placeholders)

[Browse L-Theanine on Healthylife: https://www.healthylife.com.au/browse/vitamins/stress-sleep-mood-energy/l-theanine]

[Read L-Theanine overview on Myprotein AU: https://au.myprotein.com/blog/supplements/what-is-l-theanine-l-theanine-benefits-dosage-and-side-effects/]

[Example product context referencing L-theanine: https://www.naturecan.com.au/products/pre-workout]

Disclaimer: This article is general information only and is not medical advice. If you are pregnant or breastfeeding, under 15, have a medical condition, or take medication, speak with your GP or pharmacist before using supplements.