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Baba Y, Takihara T, Okamura N. Theanine maintains sleep quality in healthy young women by suppressing the increase in caffeine-induced wakefulness after sleep onset. Food Funct ;14(15):-. View abstract.
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L-theanine may have benefits for depression, sleep, and stress. It has antioxidant and anti-inflammatory properties, as well as regulatory effects on anxiety and the immune system.
L-theanine is a non-protein amino acid found in the tea plants Camellia sinensis L., from which green and black tea are made. It's the main source of flavor in tea and has a caramel-like taste that reduces the bitter flavor of tea leaves. You can also take L-theanine as a dietary supplement.
Supplementation with 200-400 milligrams of L-theanine per day may reduce stress and anxiety in people exposed to stressful situations. L-theanine acts on the central nervous system. It influences certain pathways and receptors in the brain to reduce stress and anxiety.
L-theanine specifically reduces the release of glutamate. This excitatory neurotransmitter triggers nerve signals. High levels of glutamate can cause hyperactive nerve signals during times of stress and anxiety.
L-theanine increases the release of γ-aminobutyric acid (GABA), an inhibitory neurotransmitter that blocks nerve signals. GABA is thought to regulate anxiety, especially in people with anxiety disorders. L-theanine can also increase dopamine levels to improve mood and increase alpha-frequency brain waves. This pattern of brain activity is associated with relaxation.
Research has shown that L-theanine may enhance the efficacy of doxorubicin. This chemotherapy drug helps treat cancer. Animal studies have found that L-theanine can help more of the drug enter cancer cells and get rid of them. These results are promising, but more research is needed to know if L-theanine has the same effect on human cancer cells.
Some evidence suggests that L-theanine can support the immune system. One review noted that L-theanine may reduce the number of upper respiratory infections, such as a cold and the flu. L-theanine has been shown to help immune cells respond to bacteria and viruses, which allows your body to fight off an infection.
L-theanine may improve sleep quality due to its relaxing effects on the nervous system. A small study examined 30 participants who took 200 milligrams of L-theanine daily for four weeks. The participants had reduced sleep latency, or the time it takes to fall asleep. They also had less sleep disturbance and use of sleep medication compared to those who took a placebo.
A study of 160 people tested the effects of various supplements, including L-theanine, on sleep. Supplementing with 200 milligrams of L-theanine for seven days significantly improved sleep problems like trouble falling and staying asleep.
Some evidence suggests that L-theanine may benefit memory and attention. Supplements can improve the brain's ability to focus and remember information. One study looked at 69 Japanese adults aged 50-69 years old who took 100.6 milligrams of L-theanine. A single dose improved reaction time and working memory on cognitive tests.
L-theanine may protect brain cells from age-related damage and reduce the risk of cognitive disorders like Parkinson's disease. The high content of L-theanine in green tea is thought to lower the risk of dementia.
L-theanine may reduce depression symptoms. It can modulate the activity of neurotransmitters like dopamine. A small study found that 250 milligrams of L-theanine for eight weeks significantly reduced symptoms of depression and anxiety.
L-theanine may also positively affect symptoms of other mental health disorders like schizophrenia and schizoaffective disorder. These findings are encouraging, but it's important to discuss supplement use to treat mental health disorders with a healthcare provider.
L-theanine is available in several forms, including pills, liquids, capsules, and powders. You can also get L-theanine by drinking certain green or black teas.
You can take L-theanine on its own or in combination with other calming substances. L-theanine is often combined with magnesium. This mineral is thought to help regulate stress.
You may take L-theanine at any time of day. Taking L-theanine in the morning can support a healthy stress response. You might take it at night before bedtime to promote restful sleep.
Dosing of L-theanine for anxiety, sleep, and other health goals varies. Most studies have used doses that range from 100-400 milligrams per day. People have safely used higher doses of L-theanine without adverse side effects.
The amount of L-theanine found in teas may depend on when and where the tea is sourced and how it's brewed. Green, black, white, and oolong teas typically contain about 5-7 milligrams of L-theanine per gram.
L-theanine has been shown to be safe, even when taken in high doses. It's generally well-tolerated and not associated with health risks or side effects.
L-theanine may not be safe for people who are pregnant or breastfeeding. L-theanine can lower blood pressure levels, so it could be unsafe in people with hypotension (low blood pressure).
Drinking high amounts of caffeinated teas that contain L-theanine may cause side effects like headache, dizziness, and rapid heartbeat. Most people can safely consume about 400 milligrams of caffeine per day.
Talk to a healthcare provider before starting a new supplement, especially if you take one or more medications. L-theanine supplements may lower blood pressure. You may want to avoid L-theanine if you take one or more medications to lower blood pressure.
Due to its soothing effects, L-theanine may also have an additive effect with some sedative medications. Avoid taking supplements that contain D-theanine. D-theanine may prevent the absorption of L-theanine in the body.
It's important to choose supplements you can easily tolerate. If you have difficulty swallowing pills, you may want to purchase a liquid or powder L-theanine supplement.
L-theanine is not known to be toxic and has not been shown to have adverse side effects on health, even when taken in high doses. It's still best to follow the dosage instructions listed on the product.
Drinking more than 400 milligrams of caffeine per day may cause side effects if you are drinking teas that contain L-theanine. One 8-ounce cup of tea may contain 14-60 milligrams of caffeine.
L-theanine supplements have not been associated with any side effects. Drinking large amounts of caffeinated teas that contain L-theanine can lead to symptoms like:
L-theanine is an amino acid concentrated in tea and can be a dietary supplement. It has calming effects on the body and may reduce stress and relieve symptoms of anxiety and depression.
L-theanine supplements are considered safe and are not associated with any side effects. Talking to a healthcare provider before starting a new supplement is important to ensure it's safe and appropriate for you.
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