L-Theanine: Hormonal Effects

Evidence suggests that green tea can inhibit steroidogenesis and may decrease testosterone levels in rats. However, it is not clear if this effect is common to humans, or whether there are special considerations regarding the methods of the studies that have evidenced this. One counter argument to the contention that green tea may lower testosterone comes from the fact that many studies show an anti-anxiety and stress lowering effect for green tea, as well as L-theanine, an amino acid present within the tea. This likely relates to the evidence that L-theanine is able to interact with the neurones of the brain to increase the alpha wave state, and this has a significant calming effect, lowering the excitability of the central nervous system. This is relevant to testosterone because stress, and in particular cortisol release, is a significant factor at inhibiting testosterone synthesis. Therefore L-theanine and green tea (because of its L-theanine content) may indirectly be able to affect testosterone synthesis, through a general effect that lowers the stress response and initiates an environment more conducive to normal hormonal balance. 

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Wang, L., Brennan, M., Li, S., Zhao, H., Lange, K.W. and Brennan, C. 2022. How does the tea L-theanine buffer stress and anxiety? Food Science and Human Wellness. 11(3): 467-475

About Robert Barrington

Robert Barrington is a writer, nutritionist, lecturer and philosopher.
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