THE SCIENCE

We didn’t invent any of this.

We just brought it to golf.

Birdiegum is built on two ingredients: caffeine, the same thing in your morning coffee, just a smaller, cleaner dose, and L-theanine, a calming amino acid found naturally in green tea.

For nearly two decades, cognitive researchers have studied these two together, not separately. They figured out that when you pair them at the right ratio, something happens that neither ingredient does alone: focus sharpens, but the nerves settle. Calm shows up, but you stay sharp.

That combination has a name: the Focus Stack. It’s been validated across multiple peer-reviewed studies, in real journals, with real participants and real results. We didn’t discover it. We just took the formula that already works and put it in a piece of gum you can chew on the first tee.

If you’re the kind of person who wants to read the studies yourself, every one of them is below, with a link. No cherry-picking. No “studies show.” Just the actual research, so you can decide how legit this formula is.

What the science actually says

Here’s the short version, in plain English, before the citations.

  • Caffeine alone sharpens focus — but it also raises heart rate and can spike anxiety.
  • L-theanine alone calms the nervous system — but on its own, it does little for focus.
  • Combined at roughly a 1:2 ratio (one part caffeine, two parts L-theanine), they cancel each other’s downsides: the focus of caffeine without the jitters, the calm of L-theanine without the drowsiness.

For a golfer, that combination is the entire mental game: sharp enough to read the green, calm enough to make the putt.

The 1:2 ratio isn’t a guess

Across multiple peer-reviewed studies, one ratio kept showing up: two parts L-theanine to one part caffeine. We dosed birdiegum to match.

Same caffeine. Nearly identical L-theanine. The exact ratio scientists have been validating for nearly two decades.

The studies: read them below

2007  · Biological Psychology

Kimura, K., Ozeki, M., Juneja, L.R., Ohira, H. “L-theanine reduces psychological and physiological stress responses.”

Researchers measured what happened in people’s bodies during a stressful mental task. Participants who took L-theanine showed lower heart rate, lower physical stress markers, and less self-reported anxiety than those who took a placebo.

Why it matters for golf: the racing heart over a four-foot putt, the shaky hands on the first tee with people watching — that’s the exact stress response L-theanine reduced in this study.

Read the study on PubMed →

2008  · The Journal of Nutrition

Kelly, S.P., Gomez-Ramirez, M., Montesi, J.L., Foxe, J.J. “L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory Alpha-Band Activity and Attention Task Performance.”

Researchers measured brain activity during attention tasks. Caffeine alone increased alertness. L-theanine alone did little. But the two together shifted brain activity in a way that pointed to sharper, more focused attention — different from either ingredient on its own.

Why it matters for golf: this is the study that proved the combination behaves differently than the parts. You can’t replicate this with a cup of coffee.

Read the study on PubMed →

2008  · Nutritional Neuroscience

Owen, G.N., Parnell, H., De Bruin, E.A., Rycroft, J.A. “The combined effects of L-theanine and caffeine on cognitive performance and mood.”

Participants took 50 mg caffeine + 100 mg L-theanine — a clean 1:2 ratio. They were faster and more accurate on attention-switching tasks compared to caffeine alone, and better at ignoring distracting information during memory tasks.

Why it matters for golf: faster and more accurate, with less distraction, is the entire mental game in one sentence. This study uses the same 1:2 ratio birdiegum is built on.

Read the study on PubMed →

2010  · Nutritional Neuroscience

Giesbrecht, T., Rycroft, J.A., Rowson, M.J., De Bruin, E.A. “The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness.”

Researchers tested 40 mg caffeine + 97 mg L-theanine — nearly the exact dose in birdiegum. Participants showed significantly better accuracy on demanding mental tasks and reported feeling sharper and less tired.

Why it matters for golf: this is the study whose dosing is the closest match to birdiegum. The accuracy improvement on demanding mental tasks is the same skill you use reading a fast green or picking a club into the wind.

Read the study (Taylor & Francis) →

2016  · Medicine & Science in Sports & Exercise

Mumford, P.W., et al. (Auburn University). “Effect of Caffeine on Golf Performance and Fatigue during a Competitive Tournament.”

Auburn University tested skilled golfers (USGA handicaps 3–10) in a real 36-hole tournament. With caffeine, players averaged 2.5 strokes lower per round, hit more greens in regulation, drove the ball farther, and reported less fatigue than when they played the same tournament on a placebo.

Why it matters for golf: this isn’t a lab study with college kids doing computer tasks. This is real golfers, on real courses, in a real tournament — measurably shooting lower scores.

Read the study on PubMed →

So is focus gum a real thing?

Yes.

Five studies. Multiple research groups. Two decades. Two independent universities and three peer-reviewed journals. One consistent conclusion: caffeine and L-theanine, dosed together at roughly a 1:2 ratio, sharpen focus and steady nerves better than either ingredient alone.

We didn’t discover any of this. We took the formula that already worked and made it for golfers — so you can chew it on the first tee instead of taking a pill or drinking a third cup of coffee.

The science was settled. We just made it for golfers.

We picked the five clearest. There are dozens more.

The five studies above are the ones that translate most directly to a golfer’s experience — but they’re a fraction of the published research on this combination. Caffeine and L-theanine is one of the most-studied ingredient pairings in cognitive science. Below are the systematic reviews and meta-analyses — papers that each pool together dozens of individual trials. If you want to see how deep the well goes, start here.

Systematic reviews & meta-analyses

Each of these aggregates and statistically analyzes many separate studies. One review can represent 10–50 underlying trials.

Camfield et al. (2014), Nutrition Reviews — Meta-analysis of 11 randomized placebo-controlled trials on tea constituents (L-theanine, caffeine, EGCG); found moderate effect sizes favoring the caffeine + L-theanine combination for alertness and attention-switching accuracy in the first two hours.

Read on Oxford Academic →

Cureus (2021) — “The Cognitive-Enhancing Outcomes of Caffeine and L-theanine: A Systematic Review.” A PRISMA systematic review of clinical trials on the cognitive-enhancing effects of caffeine and L-theanine, individually and combined.

Read on PubMed Central →

Systematic review (2019), via the Alzheimer’s Drug Discovery Foundation research summary — A review of nine randomized controlled studies (270 participants total); L-theanine was associated with reductions in stress and anxiety symptoms under acute stress conditions.

See summary (Alzheimer’s Drug Discovery Foundation) →

Nutrition Reviews (2025) — Systematic review and meta-analysis of 50 randomized controlled trials on tea, L-theanine, and L-theanine plus caffeine; theanine plus caffeine conferred small-to-moderate improvements in attentional task performance and mood versus placebo.

Read on Oxford Academic →

Journal of Clinical Medicine (2025) — “The Effect of l-Theanine on Cognitive Performance: A Systematic Review and Meta-Analysis of Randomized Placebo-Controlled Clinical Trials” in healthy adults.

Read on MDPI →

Additional individual trials

Kahathuduwa et al. (2017), Nutritional Neuroscience — 200 mg L-theanine + 160 mg caffeine vs. black tea vs. placebo, five-way crossover in 20 healthy adults; the combination improved sustained attention and reduced mind-wandering (confirmed via fMRI).

Read on PubMed Central →

Hidese et al. (2019), Nutrients — Randomized, placebo-controlled, double-blind trial; four weeks of L-theanine (200 mg/day) reduced stress-related symptoms and improved sleep quality and verbal fluency in healthy adults.

Read on PubMed Central →

Neurology and Therapy (2021/2024) — Randomized, double-blind, placebo-controlled trials of AlphaWave® L-theanine; L-theanine was safe and efficacious during an acute stress challenge in healthy adults with moderate stress.

Read on PubMed Central →

There isn’t one study we’re leaning on. It’s a body of research nearly two decades deep, replicated by independent groups, pooled in multiple meta-analyses. We didn’t invent focus gum. We just read the research and made it for golfers.

A note on transparency

We’d rather you hear this from us than find it yourself. Several studies on this page disclosed industry funding: the Kelly (2008), Owen (2008), and Giesbrecht (2010) studies were supported by Unilever (which has commercial interests in tea), and the Auburn University golf study (Mumford, 2016) was funded by MusclePharm, a supplement company. Industry funding is common in nutrition research and does not by itself invalidate peer-reviewed findings — but you should know it. The most independent study cited here is Kimura (2007). More importantly, the L-theanine + caffeine effect has been replicated across many separate research groups and pooled in multiple independent meta-analyses, several of which are linked in the section above. We link every source so you can weigh the evidence yourself.

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