Theanine (sometimes referred to as "L-theanine") is an amino acid found naturally in green tea. Also available in supplement form, theanine is said to offer a number of health benefits.
Uses for Theanine
Proponents claim that theanine can help with the following health problems:
Theanine is also purported to increase concentration, promote weight loss, and boost the immune system. In addition, some proponents suggest that theanine can prevent stroke, Alzheimer's disease, and some forms of cancer.
Benefits of Theanine
To date, few clinical trials have tested the health effects of theanine. However, preliminary research indicates that theanine may offer certain health benefits. Here's a look at some key study findings:
1) Theanine and Stress
Theanine may help reduce the negative effects of stress, according to a small study published in Biological Psychology in 2007. In an experiment involving 12 people, researchers found theanine-treated participants were less likely to experience an increase in heart rate when performing a stressful task.
2) Theanine and Immunity
Taking green-tea-derived theanine and antioxidants in supplement form may help prevent the flu, suggests a study published in BMC Complementary and Alternative Medicine in 2011. Every day for five months, the study's 197 participants took either a placebo or a capsule containing theanine and catechins (a class of antioxidants found in green tea). Results revealed that incidence of flu was significantly lower in the theanine/catechin group (compared to the placebo group).
3) Theanine and Brain Health
A 2010 study from Nutritional Neuroscience suggests that a combination of theanine and caffeine may help improve cognitive performance. For the study, 44 young adults took either a placebo or a combination of theanine and caffeine prior to performing a demanding cognitive task. Researchers found that the combination of theanine and caffeine significantly improved accuracy and alertness and helped to increase focus while performing the task.
Additionally, findings from an animal-based study published in Free Radical Biology & Medicine in 2009 suggest that theanine may inhibit buildup of amyloid beta (a substance that forms the brain plaques associated with Alzheimer's disease).
4) Theanine and Depression
Theanine may help relieve depression, according to an animal-based study published in Phytotherapy Research in 2011. In tests on mice, scientists discovered that theanine produced an "antidepressant-like effect."
5) Theanine and Weight Loss
Theanine shows promise as a weight loss aid, according to animal-based research published in the journal In Vivo in 2004. In an experiment involving mice fed green tea powder, researchers found that theanine and caffeine found in the powder appeared to prevent weight gain and fight the buildup of fat.
Is Theanine Safe?
To date, little is known about the safety of taking theanine supplements in the long term. While theanine is generally considered safe when consumed in green tea, the National Institutes of Health caution against drinking more than five cups of green tea daily. Due to the caffeine content, excessive consumption of green tea may trigger certain side effects (such as headache, insomnia, irritability, diarrhea, and heartburn).
There's also some concern that taking theanine in combination with sedatives, lipid-lowering medications, and/or drugs used in chemotherapy may produce harmful effects.
Where to Find Theanine Supplements
Widely available for purchase online, theanine supplements are sold in many natural-food stores and in stores specializing in dietary supplements.
Should You Use Theanine for Health Purposes?
While it's too soon to recommend theanine supplements for any health condition, increasing your theanine intake by consuming green tea on a regular basis may help enhance your overall health.
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