L-Theanine: A Calming Counterbalance to Caffeine’s Blood Pressure Effect

L-Theanine: A Calming Counterbalance to Caffeine’s Blood Pressure Effect

Introduction

Caffeine is well-known for its ability to boost alertness and focus. However, its stimulating properties can also temporarily influence cardiovascular measures such as heart rate and blood pressure. This can be a consideration for individuals who are sensitive to stimulants or who consume caffeine regularly. Emerging research suggests that L-theanine—a naturally occurring amino acid in green tea—may help balance these effects, supporting a calmer physiological response without reducing cognitive performance.

What is L-Theanine?

L-Theanine (L-gamma-glutamylethylamide) is found in high concentrations in certain teas, particularly shade-grown varieties like matcha and gyokuro. It is valued for promoting a relaxed yet alert mental state, often described as “calm focus.” 

Well-controlled clinical trials involving healthy adults indicate a single dose of L-theanine improves attention and working memory (100-200 mg) and helps fortify stress resilience (200 mg), while longer term use (200-400 mg/day) has been shown to support positive mood, stress resilience and sleep quality (1-6). 

The L-Theanine–Caffeine Balance

Caffeine stimulates the central nervous system by blocking adenosine receptors, which can lead to sharper focus but also increases in heart rate and vascular tension. L-theanine appears to work differently—supporting alpha brain wave activity and modulating excitatory neurotransmitters—leading to a smoother, more controlled alertness.

When taken together, L-theanine may temper caffeine’s stimulating edge. Clinical and neurophysiological studies have reported that this combination can (7):

  • Promote sustained attention without the “jitters.”

  • Support reaction time and working memory while moderating overstimulation.

  • Contribute to a more balanced cardiovascular response to caffeine intake.


Attenuating Caffeine’s Blood Pressure Effect

L-theanine can support relaxation of the vascular system and reduce the acute rise in blood pressure sometimes experienced after caffeine consumption. This action is primarily attributed to its ability to modulate the autonomic nervous system and neurotransmitter activity (4).

The ability of L-theanine to help maintain blood pressure within the normal range, combined with its ability to promote mental performance and stress resilience, suggests that L-theanine could be ideal for situations where both cognitive focus and cardiovascular stability are important.

Practical Considerations

  • Ratio: Many experts recommend combining L-theanine and caffeine in a roughly 2:1 ratio (e.g., 200 mg L-theanine with 100 mg caffeine) for optimal synergy.

  • Timing: Theanine is absorbed within about 30-50 minutes, matching well with caffeine’s onset.

  • Source: Green tea naturally contains both caffeine and L-theanine, but supplementing allows for more precise dosing.

Bottom Line

L-theanine offers a unique way to help maintain mental clarity and composure while moderating some of caffeine’s more stimulating cardiovascular effects. For those who enjoy the focus that caffeine brings but want a smoother experience, this amino acid—especially when combined with caffeine—can be a valuable tool in supporting balanced energy and attentiveness.

References

1. Baba Y, Inagaki S, Nakagawa S, Kaneko T, Kobayashi M, Takihara T. Effects of L-theanine on cognitive function in middle-aged and older subjects: a randomized placebo-controlled study. J Med Food. 2021;24(4):333-341. doi:10.1089/jmf.2020.4803

2. Foxe JJ, Morie KP, Laud PJ, Rowson MJ, de Bruin EA, Kelly SP. Assessing the effects of caffeine and theanine on the maintenance of vigilance during a sustained attention task. Neuropharmacology. 2012;62(7):2320-2327. doi:10.1016/j.neuropharm.2012.01.020

3. Dassanayake TL, Wijesundara D, Kahathuduwa CN, Weerasinghe VS. Dose-response effect of L-theanine on psychomotor speed, sustained attention, and inhibitory control: a double-blind, placebo-controlled, crossover study. Nutr Neurosci. 2023;26(11):1138-1146. doi:10.1080/1028415X.2022.2136884

4. 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. J Physiol Anthropol. 2012;31(1):28. doi:10.1186/1880-6805-31-28

5. Hidese S, Ogawa S, Ota M, et al. Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial. Nutrients. 2019;11(10):2362. doi:10.3390/nu11102362

6. Williams JL, Everett JM, D'Cunha NM, et al. The effects of green tea amino acid l-theanine consumption on the ability to manage stress and anxiety levels: a systematic review. Plant Foods Hum Nutr. 2020;75(1):12-23. doi:10.1007/s11130-019-00771-5

7. Anas Sohail A, Ortiz F, Varghese T, et al. The cognitive-enhancing outcomes of caffeine and L-theanine: a systematic review. Cureus. 2021;13(12):e20828. doi:10.7759/cureus.20828