Theanine

Theanine

• L-theanine is a water-soluble amino acid found in green tea and mushrooms. Purified L-theanine is available as an oral dietary supplement and is used for its perceived antioxidant and relaxant effects. Several in vitro and animal studies suggest lipid-lowering, neuroprotective, anti-obesity, and antitumor properties. Other lab studies suggest L-theanine may affect levels of some neurotransmitters, prevent beta-amyloid-induced cognitive dysfunction, and promote longevity in C. elegans.

Mechanism of Action:

• The underlying mechanism of L-theanine is to increase inhibitory neurotransmitter levels as well as act directly to block overproduction of excitatory neurotransmitters. L-theanine is a glutamic acid analog, a compound chemical similar to the neurotransmitter glutamate.

Dosage:

• Studies reporting an anxiolytic effect used single doses of theanine 200-250 mg. Short-term studies conducted for psychiatric disorders examined doses ranging from 240 to 400 mg per day in divided doses. Single-dose studies evaluating effects on cognitive performance and mental alertness combined caffeine with L-theanine doses of 97-100 mg.

Evidence:

• In a double-blind trial of adjunctive L-theanine for generalized anxiety disorder, there were no significant effects on anxiety although positive effects on sleep were observed. Other small trials in patients with various conditions also suggest improvements in sleep quality and possibly depression, anxiety, and cognitive impairments although larger well-designed trials are needed.

• Some trials evaluating L-theanine with caffeine suggest improvements in cognitive performance although effects observed with caffeine alone in one study were lost with concomitant L-theanine. When combined with antipsychotic treatment, L-theanine alleviated anxiety and related symptoms, and improved sleep in patients with schizophrenia.

• Epidemiological data suggest green tea consumption may contribute to stroke prevention, but it is unclear whether L-theanine alone may confer this benefit. Preclinical studies suggest that L-theanine enhances chemotherapeutic effects of doxorubicin and idarubicin and alleviates adverse effects from use of these agents.

• However, patients undergoing chemotherapy should discuss the use of L-theanine with their physicians because these effects are not based on clinical trials, and epigallocatechin-3-gallate (EGCG) in green tea reduces activity of the chemotherapy drug bortezomib.

Precautions:

• Information regarding adverse reactions to theanine alone (versus combined with caffeine, as in tea) is lacking. Clinical trials used small numbers of participants and reported poorly on adverse events. One study among elderly participants recorded a higher number of reported headaches among those receiving four doses of theanine 250 mg.

Interactions:

• Lab experiments that suggest L-theanine may increase efficiency of chemo-therapy drugs or reduce side effects have not been confirmed in humans.

• Patients undergoing chemotherapy should discuss the use of L-theanine with their physicians because safety data in cancer patients are lacking, and another component found in green tea called epigallocatechin-3-gallate (EGCG) reduces activity of the chemotherapy drug bortezomib.