L-theanine: What Is It And What Are The Benefits?
* Verified by a US-based board-certified doctor.
L-theanine at a Glance
L-theanine is a non-essential amino acid, meaning humans do not naturally produce it. It also means it’s not necessary for our survival. However, taking L-theanine may positively affect chemicals in the brain, including serotonin and dopamine.
We find L-theanine in certain mushrooms, black tea, and green tea. It is very similar to glutamate, an amino acid our body does produce used to carry nerve impulses to our brain.
This chemical may help improve stress levels and mood. This compound is considered safe, though scientists are still conducting high-quality research to understand its effects fully.
History of L-theanine
L-theanine was first found in 1949 as a component of green tea. Later, it was extracted from gykuro leaves, used for a specific type of Japanese green tea.
In 1964, Japan approved L-theanine for unlimited use in foods and beverages, not including infant food. After, the US approved L-theanine as safe for use, and you can buy the chemical as a supplement in most countries that permit the sale of supplements.
In one cup of green tea, there is 20mg of L-theanine, but most supplements have anywhere from 50-250mg.
While the L-theanine found in supplements is the same compound as that in green tea, it’s artificially manufactured in a lab.
Why Take L-theanine?
Helps You Sleep
A 2018 study found that after taking 450-900 mg of L-theanine each day for 8-weeks, people reported improved sleep. Note that these participants were on antidepressants for anxiety.
L-theanine may impact our brain's amino acids that regulate sleep, helping us sleep more deeply and quickly.
The effect of L-theanine on sleep extends to boys with ADHD, those with schizophrenia, and animals.
A 2012 study found that people who took 100mg of L-theanine performed better at an attention task than those who took a placebo. Considering many people find green and black tea to improve their focus, this makes anecdotal sense, too.
Researchers continue to study L-theanine to fully understand its impact on mental focus; early results suggest it can positively impact attention and focus.
Reducing Stress & Anxiety
A few studies found that L-theanine combats stress and anxiety. Another study found that L-theanine helped those suffering from schizoaffective disorder or schizophrenia by improving their symptoms and decreasing anxiety.
L-theanine therefore may combat stress while not making you drowsy.
It’s thought that L-theanine reduces our resting heart rate. When you’re amped up, your heart rate increases; however, your resting heart rate lowers when fully relaxed. Thus, if L-theanine reduces your resting heart rate, it makes you feel more at ease.
Alt-text: stressed woman
L-theanine may act as an anti-inflammatory, and these are known to combat illness. Some studies suggest that L-theanine makes you less likely to contract the flu or get a cold since L-theanine may boost the immune system.
Helps You Lose Weight
L-theanine found in green tea produces an umami flavor or a savory taste. This may cause a reduced appetite.
Additionally, drinking a low-calorie hot beverage like green tea in place of a snack may help with weight loss.
Thus, when used correctly, L-theanine may help you drop a few pounds.
Heightened Cognitive Performance
Although the research is still being conducted, early findings suggest that L-theanine can improve brain function.
In combination with caffeine, L-theanine may improve alertness and skill with numbers. On its own, this compound may boost your reaction times and attention.
L-theanine may benefit both your physical and mental health, producing neuroprotective effects responsible for boosting in brainpower.
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One study found that those whose blood pressure increased due to a stressful event could lower their blood pressure by taking L-theanine. Caffeine had similar results, but it wasn’t quite as beneficial.
Since high blood pressure puts you at risk of strokes, heart attacks, and more, L-theanine could have powerful effects. Given L-theanine is linked to stress reduction, it makes sense that it might lower blood pressure as a result.
L-theanine may aid chemotherapy drugs in fighting tumors.
Although there’s no direct evidence for it, some studies show that tea drinkers are less likely to get cancer, with one study finding a 32% reduction in pancreatic cancer rates in women who drank green tea.
L-theanine is only administered by mouth. The compound has been most thoroughly studied in short-term (8-week) oral uses with doses up to 400mg daily.
L-theanine has limited side effects. It may lead to sleepiness or headaches, and in more rare cases, dizziness or an upset stomach.
Call your doctor immediately if you experience:
- Extreme diarrhea
- Extreme vomiting
- Inability to think clearly
- Wheezing, chest tightness, severe cough
- Signs of low blood pressure, fainting, excess thirst
Side effects this extreme are rare.
Do not take L-theanine if you are breastfeeding, pregnant, or plan to become pregnant soon. This chemical can cause drowsiness, so exercise caution when operating heavy machinery.
There are two moderate interactions to be aware of.
Antihypertensive (medication for high blood pressure) drugs. L-theanine may decrease blood pressure, so combining it with these meds can cause your blood pressure to drop too much.
Examples of antihypertensive drugs include captopril, enalapril, losartan, valsartan, and furosemide.
Stimulant drugs. Since L-theanine may lead to relaxation and a slowing down of your nervous system, taking a stimulant with this supplement will negate the stimulant's effectiveness.
L-theanine is sold as a supplement in many countries and may have a variety of impacts. This chemical is thought to help you sleep, reduce anxiety and stress, improve mental focus, boost your immune system, help you lose weight, and more.
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