L-Theanine in Memopezil: 100 mg of the Calm-Focus Amino Acid

L-theanine is an amino acid found mainly in tea leaves, and it is the calmest ingredient on the label.

Each Memopezil serving lists "L-Theanine" at 100 mg. The label does not say whether it comes from tea or is made another way. It also lists no caffeine and no tea extract, so you get the amino acid without the stimulant that usually comes with a cup of tea. (Memopezil sales page)

The sales page says L-theanine "promotes relaxation without causing drowsiness." We quote that and do not repeat it as fact. The trials below measured reaction time, mood and sleep, not drowsiness, so the claim is not what they tested.

Of the five lines, L-theanine has the simplest story: one compound, a clear dose in trials, and effects that show up within an hour or within weeks.

It shows small effects on speed of attention and on stress and sleep, and little on memory itself.

The 4-week trial. A randomized, placebo-controlled crossover trial in 30 healthy adults with an average age of 48 gave 200 mg a day of L-theanine. Depression, trait anxiety and sleep-quality scores improved compared with placebo. It was a small study. (Hidese 2019, L-theanine 200 mg)

The 2025 review. The authors screened 50 randomized trials of tea or its compounds and pooled 15. L-theanine alone beat placebo on choice reaction time in the first hour, with a standardized difference of -0.35. L-theanine plus caffeine showed small-to-moderate gains at hours one and two. The confidence ranges often left the size and direction uncertain, and the authors asked for research at tea-equivalent doses in everyday life. (Payne 2025, L-theanine meta-analysis)

The 2014 analysis. A meta-analysis of 11 placebo-controlled studies looked at single doses of tea compounds, alone or with caffeine, on attention and mood. It studied acute effects, not months of use. (Camfield 2014, L-theanine meta-analysis)

The pattern is steady and modest. L-theanine may help you react a little faster for a short time and may ease stress. None of these studies measured memory as the main goal, so they do not support the memory claim.

The trials we read described L-theanine as well tolerated. We found no source listing a serious interaction. We still do not take that as a clean bill of health.

• It is a calming compound, so ask a pharmacist about taking it with sedatives or blood pressure medicine.
• The studies are small and short, four weeks at the longest here.
• Memopezil has four other ingredients, and the label caution applies to the whole capsule: consult a physician if you have a known medical condition.