L-Theanine

Theanine is one of the more straightforward things on our shelves, so it's worth being clear about the few situations where it really doesn't belong. These are the questions our naturopaths ask in store.

A good fit if

• You're an adult who wants the daytime kind of alertness tea is known for, without adding more caffeine
• You already have caffeine and want to try the pairing that has better evidence than caffeine alone
• You prefer a single-ingredient product where the milligrams on the label are the whole story
• Your health history is straightforward, you take no prescription medicines and you're not pregnant or breastfeeding
• You're happy to judge it over a few days rather than expecting a dramatic first dose

Check with us first if

• You take blood pressure medicines. Theanine has been studied for effects on blood pressure and the combination hasn't been well studied, so talk to us before taking both.
• You take sedatives, sleep medicines or anything that already makes you drowsy. Theanine isn't a sedative itself, but night-time formulas containing it usually are.
• You already take a night-time, magnesium or focus formula. Check whether it contains theanine before adding a single-ingredient product, because it's easy to double up without noticing.
• You're keeping track of caffeine. Many theanine products are sold in caffeinated blends, and it's the caffeine, not the theanine, that has the tighter limits.
• You're buying it because anxiety is the problem. The evidence there is modest and short term, and it's worth talking to a practitioner rather than just picking something off the shelf.
• You're buying from an overseas website. Those products aren't regulated by the TGA for quality and safety, and the Australian dose limit and label warnings don't apply to them.
• You take any prescription medicine at all. A quick check with your doctor, pharmacist or our naturopaths first is the sensible step.

• Isolated L-theanine capsule or tablet. Best known for: The usual Australian format, and the one that matches the doses used in research. Absorption: Dissolves in water and is absorbed from the small intestine; blood levels peak within about an hour. Typical use: One 200 mg capsule a day. The label states the theanine milligrams directly, with nothing else to work out.
• Branded fermentation-derived theanine (Suntheanine, AlphaWave and similar). Best known for: Made using enzymes and supplied as the pure L-form, with a certificate of identity behind it. Absorption: No absorption advantage over generic L-theanine has been shown; the difference claimed is purity and consistency. Typical use: Named on the ingredient list of most Australian one-a-day products, at the same milligram strength.
• Bulk theanine powder. Best known for: Splitting or adjusting a dose, and mixing it into a drink rather than swallowing a capsule. Absorption: The same as the capsule; it's the same molecule without a shell around it. Typical use: You measure it by the scoop, so a set of scales matters more here than with a pre-measured capsule.
• Theanine plus caffeine (pre-workouts, energy and focus blends). Best known for: This combination has better evidence for attention than either ingredient tested alone. Absorption: Both are absorbed quickly; the caffeine is what you'll feel first, and the theanine isn't the sedating half. Typical use: Ratios vary widely between products; the caffeine number is the one to add up across your whole day.
• Theanine inside a magnesium, herbal or night-time formula. Best known for: It turns up as one line on a longer ingredient list, rather than as the point of the product. Absorption: Absorbed the same way, but the theanine dose is usually well below the 200 mg used in trials. Typical use: Easy to double up on without noticing if you also take a theanine product on its own.
• Green tea, matcha or black tea. Best known for: The wholefood route, and the only way most people have ever come across theanine. Absorption: The same molecule, delivered with caffeine and catechins from the same leaf. Typical use: Even several cups a day fall well short of a single capsule; it's a habit, not a dose.

Reference values. There aren't any. Theanine isn't an essential nutrient, so the NHMRC sets no Nutrient Reference Value, Recommended Dietary Intake or Estimated Average Requirement for it. Nothing goes wrong if you never have any.

Typical supplemental range. Australian labels have settled almost entirely on 200 mg per capsule or tablet, taken once a day. Combination formulas, such as night blends, magnesium products and focus or pre-workout powders, usually contain far less, often 50 to 100 mg, which is a real difference from a single-ingredient product. Powders are the exception, because the dose is whatever you scoop.

Upper level. There's no NHMRC Upper Level of Intake for theanine. The only Australian limit is a regulatory one, set on Australia's permitted ingredients list, and it's quoted in full in the Australian status section on this page.

Worth knowing. Timing is the question people ask least and should ask most. Trials measure effects 30 to 60 minutes after a single dose, and the combination studies found their attention effects in the hour after that, so this works on the day rather than building up. Longer studies of up to eight weeks didn't find a bigger effect over time. What you need depends on your age, diet and health, so talk to one of our naturopaths.

Food first, where the diet allows it.

• Green tea, brewed, one cup: median 8 to 30 mg of theanine: roughly a tenth of a standard capsule
• Matcha, whisked whole leaf: more theanine per gram of leaf than an infusion, because the leaf is swallowed rather than steeped
• Shade-grown Japanese leaf teas such as gyokuro: shading before harvest raises leaf theanine; the amount depends on the growing method, not the brand
• Black tea, brewed: same plant and a similar order of magnitude; oxidation removes catechins, not theanine
• Bay bolete mushroom (Boletus badius): the only well-documented natural source outside the tea plant, and not a practical dietary one

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• Pregnancy and breastfeeding. Australian labels must state 'Not recommended for use by pregnant and lactating women'.
• Children and teenagers. Australian labels must state 'Adults only'.
• Australian medicines cap theanine at 450 mg in a maximum recommended daily dose, so don't take more than the label says.
• By mouth only. The rules allow no other way of taking theanine.
• Blood pressure medicines. The effects could add together, and the combination isn't well understood.
• Sedatives and sleep medicines. Theanine isn't sedating, but the combination products it comes in often are.
• Doubling up. Theanine is often tucked inside magnesium, night-time, focus and pre-workout formulas.
• Total caffeine. Theanine is often sold inside caffeinated blends, and caffeine has the tighter Australian limits.
• Anxiety, low mood or ongoing sleeplessness. See a health professional; the evidence here is modest and short-term.
• Products bought from overseas websites aren't regulated by the TGA for quality and safety.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before you start.