L-Theanine For Mood & Mental Alertness

L-theanine is a really fascinating compound found mostly in green tea, matcha and guayusa and the edible bay boletes mushroom, Xerocomus badius. It is thought to be the reason behind the calming and relaxing characteristic of beverages like tea (Juneja et al., 1999). After all, when you want something to relax you after a hard day, it’s quite often tea that is called for.  

L-Theanine is an amino-acid which is not found in proteins. It is also known as gamma-glutamylethylamide. L-theanine is the major one in tea where it forms 1 – 2% by dry weight  and this corresponds to 25-60mg per 200ml serving (Cartwright et al., 1954).

We know of some who drink tea after they have drunk too much coffee and this could well be due to the presence of theanine because it counters the effects of too much caffeine but doesn’t cause drowsiness or sleep.

Clinical Evidence

The evidence for theanine’s benefits comes from clinical studies which indicate that between 50 mg and 200 mg helps naturally stimulate alpha wave activity in the brain. This is associated with mental alertness whilst maintaining a relaxed state.

In animal models, l-theanine shows activity in decreasing blood pressure and improving learning ability (Kim et al., 2009).

As well as the aforementioned improvement in mood state, a human study by Higashiyama and his team (2011) found that L-theanine significantly improved attentiveness and reaction responsiveness.  It is not addictive. The other benefits are as follows:

1. Promotes Relaxation and Reduces Stress

L-theanine increases the production of alpha brain waves, which are associated with a calm, relaxed mental state. Unlike sedatives, it helps reduce stress without making you sleepy, making it ideal for managing everyday tension or anxiety.

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2. Improves Focus and Cognitive Performance

L-theanine can enhance attention, memory, and focus, especially when combined with caffeine. This combination is common in tea, where theanine smooths out caffeine’s stimulating effects, providing alertness without jitteriness.

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3. Supports Better Sleep Quality

While it doesn’t act as a sedative, L-theanine can help improve sleep quality by reducing racing thoughts and calming the nervous system. Users often report falling asleep more easily and experiencing deeper, more restorative sleep.

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4. May Lower Blood Pressure

Some studies suggest that L-theanine can help moderate blood pressure spikes during stressful situations, contributing to cardiovascular health over time.

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5. Enhances Mood

L-theanine promotes the production of neurotransmitters such as dopamine and serotonin, which can help improve mood, reduce symptoms of anxiety, and support emotional well-being.

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6. Supports Immune Function

Emerging research suggests L-theanine may help strengthen the immune system, potentially increasing the body’s resistance to infections by enhancing the activity of certain immune cells.

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7. Neuroprotective Potential

There’s some evidence that L-theanine may have antioxidant and neuroprotective effects, helping protect brain cells from oxidative stress and supporting long-term brain health.

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Usage Notes:

• Typical doses range from 100–400 mg per day, often in supplement form.

• It’s generally safe, non-addictive, and well-tolerated with few reported side effects.

• It works best when paired with caffeine for focus, or taken alone for relaxation and sleep support.

Products

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Taiyo International Inc., in Minneapolis, Minn. (www.taiyointernational.com) offer the ingredient as 100% pure L-isomer under the brand name Suntheanine® for use in formulations. This product is produced by their patented fermentation product which mimics the creation process in the green tea leaves themselves.

It is often consumed as a supplement, usually one or two 200mg capsules, to be taken with food. Take a couple when waking up and then wait a few hours before taking the next dose.  It is an effective alternative to St John’s Wort which is also used for its calming abilities and doesn’t interfere with birth control pills.  I suggest trying it as a supplement from suppliers like Solgar. If green tea is more your thing than a capsule, then try Pukka‘s green tea brand.

Some of the main UK brands & sellers of L‑Theanine

• Lamberts — Widely regarded in the UK as one of the “top” names for L‑Theanine capsules. Their L‑Theanine 200 mg capsules are popular for offering a clean, free‑form product suitable for vegetarians/vegans.

• Myprotein — The well‑known UK-based sports‑nutrition brand also offers a 100% L‑Theanine powder. Since Myprotein is one of the largest and most accessible supplement retailers in the UK, it’s a common entry point for many people wanting theanine. 

• Nature’s Best — They market L‑Theanine 200 mg capsules, sourced from green tea extract, often promoted for relaxation, focus and sleep support. 

• Cytoplan — Cytoplan offers a higher‑strength L‑Theanine capsule (e.g. 250 mg per capsule), and positions their product as bio‑effective and aimed at promoting calm, sleep or cognitive benefits.

• Smaller / sports‑nutrition‑oriented retailers / brands — There are also more niche or smaller UK retailers offering L‑Theanine, sometimes as part of broader “wellbeing” or “mind & focus” supplement lines (some examples from UK supplement‑shop listings).

References