The psychoactive amino acid derivative L-theanine has only recently begun to be researched as a possible treatment for hypertension. Due to its similarity to the neurotransmitter glutamate, L-theanine is able to cross the blood-brain barrier and affect a number of neurochemical pathways. Although it is found naturally in tea, concentrated extracts are generally used to achieve the therapeutic dose. Tea leaves also contain caffeine, which many doctors recommend eliminating from a blood pressure control diet. L-theanine has not yet been proven effective in the treatment of high blood pressure. You should consult with your physician before taking supplements containing L-theanine.
L-Theanine Studies
The journal "Trends in Food Science and Technology" first published the research on the anti-hypertensive properties of L-theanine in 1999. In its article, the Department of Nutritional Biochemistry at the University of Shizuoka found a strong correlation between the administration of high doses of L-theanine and the reduction of blood pressure in a hypertensive population. In 2008 researchers at the University of Bristol published a study in "Psychopharmacology" that replicated these findings. They found that subjects taking L-theanine alongside caffeine reported lower blood pressure levels than those taking caffeine alone.
Mechanism of Action
L-theanine is believed to lower blood pressure through one of two neurochemical pathways. It increases the level of the neurotransmitter GABA throughout the brain. GABA, the brain's stress relieving inhibitory chemical, is manipulated by anti-anxiety medications like diazepam. Unlike diazepam, L-theanine does not appear to be habit forming and may be useful in reducing psychogenic hypertension. Although L-theanine's effects on the neurotransmitter serotonin are not well understood, it is possible that it may also lower blood pressure by affecting its levels in the brain as well.
Interactions and Contraindications
L-Theanine is not known to produce any adverse reactions when taken with pharmaceutical drugs, according to Drugs.com. Neither are there any reports of the compound interacting with any herbs or supplements, although some research does suggest that it may increase the efficacy of doxyrubicin, a drug used in cancer treatment. L-Theanine is believed to be safe to use for patients with any condition.
Safety
Some people develop headaches when they take high doses of L-theanine. According to Drugs.com, it is difficult to consume enough L-theanine to produce a toxic reaction. In rare cases, you may develop dizziness or gastrointestinal discomfort from supplements containing L-theanine. Although the FDA does not recognize it as an effective treatment for any condition, they have reaffirmed L-theanine's classification as "Generally Recognized As Safe"; however, until longitudinal human studies have been performed in a large population, the long-term therapeutic use of L-theanine cannot be definitively considered safe.
References
- "Psychopharmacology"; Time for Tea: Mood, Blood Pressure and Cognitive Performance Effects of Caffeine and Theanine Administered Alone and Together; P.J. Rogers, et al; June 2008
- "Trends in Food Science and Technology"; Review: L-Theanine---A Unique Amino Acid of Green Tea and its Relaxation Effect in Humans; L.R. Juneja, et al; June 1999
- Reduction Effect of Theanine on Blood Pressure and Brain 5-Hydroxyindoles in Spontaneous Hypertensive Rats; Hidehiko Yokogoshi; 1995
- "Biological Psychology"; L-Theanine Reduces Psychological and Physiological Stress Responses; K. Kimura, et al; January 2007
- "Biological Psychology"; The Effects of L-Theanine, Caffeine and Their Combination on Cognition and Mood; C.F. Haskell, et al; February 2008
- "Journal of Clinical Psychiatry"; L-Theanine Relieves Positive, Activation, and Anxiety Symptoms in Patients with Schizophrenia and Schizoaffective Disorder: An 8-Week, Randomized, Double-Blind, Placebo-Controlled, 2-Center Study; M.S. Ritsner, et al; 2010
