Key Takeaways
L-theanine promotes calm alertness that may enhance focus without causing drowsiness.Pairing caffeine and L-theanine can boost attention and mental clarity while reducing the jittery edge often caused by coffee alone.The combo is safe for most healthy adults in moderation.
A new “biohacking” trend is circulating online: adding 200 milligrams of L-theanine to your coffee. The combination is supposed to improve focus, offer steady energy, and reduce caffeine crashes. Experts say there’s some truth to these claims.
How Does L-Theanine Affect Focus?
L-theanine, an amino acid found in green tea, affects the brain chemicals that promote a state of calm alertness rather than sedation, according to Luke Barr, MD, a board-certified neurologist and chief medical officer at SensIQ.
“In short, it enhances mental clarity and reduces anxiety without making you drowsy,” Barr told Verywell. “That can improve focus indirectly by reducing mental noise and tension.”
This effect can be especially beneficial under pressure.
“L-theanine supports focus by increasing brain wave activity associated with relaxed alertness,” said Oscar Coetzee, MS, DCN, senior director of clinical education at Designs for Health.
“It also influences dopamine and serotonin, supporting a balanced mood and reducing stress-induced distractions,” he added.
Together, these mechanisms may help clear mental fog and promote steady concentration, especially when you need to stay sharp without feeling overstimulated.
How Does Coffee Affect Attention Span?
Caffeine, the main active compound in coffee, helps you feel alert by blocking adenosine, a brain chemical that makes you sleepy. When caffeine steps in, your brain accelerates its activity and releases more “feel-good” chemicals like dopamine and norepinephrine.
That’s what gives you the familiar caffeine buzz—sharper focus, quicker thinking, and an overall energy lift.
Caffeine also stimulates the adrenal system, triggering a process called gluconeogenesis, which is the release of stored energy into the bloodstream. According to Coetzee, this fuels the brain with more glucose, which in turn boosts levels of key neurotransmitters like dopamine and norepinephrine.
“The result is improved alertness, reaction time, and mental energy,” he said
Still, caffeine’s benefits can come with trade-offs. “Caffeine’s effects can also increase heart rate and jitteriness, particularly in those who are sensitive or consume it on an empty stomach,” said Barr.
What Happens When You Mix Them Together?
Combining L-theanine and caffeine appears to create a synergistic effect, with each one enhancing the other’s benefits while minimizing the downsides.
Evidence supports this: Research shows that pairing 200 milligrams (mg) of L-theanine with 160 mg of caffeine, roughly the amount in a strong cup of coffee, improves attention-switching accuracy, reaction time, and sustained focus compared to caffeine alone.
“L-theanine can smooth out the overstimulating effects of caffeine by promoting relaxation without sedation,” said Coetzee. “This powerful combo often leads to what’s called calm focus, where you get clarity and alertness from caffeine, without the jittery edge.”
He added that this makes it easier to focus, switch between tasks, and maintain attention.
Are There Risks to Consider?
Combining L-theanine and caffeine is safe and well-tolerated for most healthy adults.
“There are no known adverse interactions,” says Coetzee. “However, individual responses can vary. Those who are highly sensitive to caffeine or L-theanine may experience mild gastrointestinal discomfort, headaches, or changes in blood pressure.”
According to Barr, people with low blood pressure should be cautious, as L-theanine may lower it further. “Individuals taking medications that affect serotonin, dopamine, or blood pressure should consult their physician before supplementing,” he said.
If you’re new to the combination, Coetzee recommends starting small: “Try a low dose (100 mg of L-theanine to match 100 mg of caffeine) to assess personal tolerance.”
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