Written by Jessica Patella, ND. Study participants with high blood pressure significantly decreased both systolic and diastolic blood pressures while taking 200 mg of theanine daily for 7 days compared to those participants in the caffeine plus placebo group. 

blood pressureOn average, Americans rate their stress level as 4.9 on a 10-point scale, where 1 is “little or no stress” and 10 is “a great deal of stress” 1. It is known that stress can elevate blood pressure by releasing stress hormones that increase vasoconstriction (tightening of the vessels, therefore increasing the pressure) 2. A recent study found that supplementing with L-theanine can decrease the rise in blood pressure during times of stress 3.

Both L-theanine and caffeine, components of green tea, have been shown to have beneficial effects on brain functioning and mood 3. L-theanine is an amino acid found in green tea leaves that has anti-stress properties and has been shown to lower blood pressure 3,4. Caffeine has the opposite effect of a stimulant that can increase blood pressure, but it can improve mental performance 5.

The first study to research both L-theanine and caffeine under conditions of acute psychological and physical stress included 16 healthy volunteers (8 men, 8 women; ages 22.8 +/- 2.1 years) 3. It was a cross-over design in which three separate trials were performed. Participants took either a placebo plus L-theanine (200mg), a placebo plus caffeine (100 mg) or a placebo only. Each trial was separated by 7 days 3.

Participants would arrive at the study center and take their trial supplement, to which they were blinded. Psychological stress load was then implemented by having an auditory target detection task (5 minutes) and a math mental test (10 minutes) that were each implemented twice 3. A Cold pressor test was then used to induce physical acute stress, where participants had to immerse their right hand in a bucket of slushy ice water for 1 minute 3.

The Profile of Mood States questionnaire and the visual analog scale were taken before supplementation and after the mental and physical tasks were completed. Blood pressure was recorded throughout the testing period of psychological and physical stress for a total of 30 times over a period of about 1 hour 3.

For analysis of the data, participants were divided into a low blood pressure response group and a high blood pressure response group. Participants with an increase in systolic blood pressure in the range of 9.46 to 33.88 mmHg were considered a high blood pressure response group to stress. It was been shown that a large blood pressure response to stress may be a risk for hypertension at mid-life 2.

Participants in the large blood pressure response group showed a significant decrease in the rise of systolic and diastolic blood pressure while taking L-theanine compared to caffeine and placebo (Systolic P-values: AMT*4 P=0.010, AMT5 P=0.020, AMT6 P=0.009; Diastolic P-values: AMT4 P=0.006, AMT6 P=0.039) 3.

L-theanine also decreased subjective stress, based on the visual analog scale and Profile of Mood States questionnaire compared to placebo (P=0.004) 3.

In conclusion, L-theanine reduced anxiety and reduced the rise in blood pressure in high stress response adults 3. This was the first study of its kind, so future research is needed to confirm the results

*AMT=Measurements “After Mental Tasks”. A total of 30 data points were recorded in the estimated 1 hour testing period.

Source: Yoto, Ai, Mao Motoki, Sato Murao, and Hidehiko Yokogoshi. “Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses.” Journal of physiological anthropology 31, no. 1 (2012): 28.

© Yoto et al.; licensee BioMed Central Ltd. 2012

Posted August 18, 2016.

Jessica Patella, ND, is a naturopathic physician specializing in nutrition and homeopathic medicine and offers a holistic approach to health.  She earned her ND from Southwest College of Naturopathic Medicine in Tempe, AZ, and is a member of the North Carolina Association of Naturopathic Physicians. Visit her website at: www.awarenesswellness.com.

References:

  1. Association AP. Stress In America: Paying with our Health. February 4, 2015 2015.
  2. Matthews KA, Katholi CR, McCreath H, et al. Blood pressure reactivity to psychological stress predicts hypertension in the CARDIA study. Circulation. 2004;110(1):74-78.
  3. Yoto A, Motoki M, Murao S, Yokogoshi H. Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses. Journal of physiological anthropology. 2012;31(1):1.
  4. Yokogoshi H, Kobayashi M. Hypotensive Effects of y-glutamylmethylamide in spontaneously hypertensive rats. Life Sciences. 1998;62(12):1065-1068.
  5. Owen GN, Parnell H, De Bruin EA, Rycroft JA. The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutr Neurosci. 2008;11(4):193-198.
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