I get asked about focus more than almost anything else, usually by someone holding a can of MAC Energy or a goBHB® shot and wondering if the brain claims on the label hold up. The best new answer on ketones and cognition came out this spring: a systematic review and meta-analysis in Frontiers in Nutrition that pooled the randomized trials on exogenous ketones and mental performance.
The short version is that ketones did improve cognitive test scores on average, the effect was modest, and the individual studies were all over the place. Below I’ll go through what the review found, two trials I think are worth knowing, what that means for the goBHB products on shelves, and where I think the evidence actually stands.
What the 2026 Meta-Analysis Found on Ketones and Cognition
Bonnechère, Stephens, Boileau, Ducker and Stubbs published the review on March 25, 2026. They searched PubMed, Web of Science and Embase through October 2025 for randomized controlled trials of exogenous ketones that measured cognition. The review covered 1,602 participants, and 29 trial protocols with 1,117 people went into the pooled analysis. The study was registered in advance with PROSPERO (CRD42023471727).
The products were a mixed bag: ketone esters, BHB salts like goBHB, MCT oils and even coconut oil. The people were mixed too. Some trials studied healthy adults and athletes, some studied people under acute stress like hard exercise or low oxygen, and others investigated people with mild cognitive impairment, Alzheimer’s disease, Parkinson’s disease, multiple sclerosis or type 1 or 2 diabetes.
Pooled together, exogenous ketones improved cognitive performance compared with placebo, with a standardized mean difference of 0.29 (95% CI 0.16 to 0.41, p < 0.001). The authors called that modest, and I agree. By the usual rule of thumb, 0.2 is a small effect and 0.5 is medium, so this sits at the low end.
Dose looked like it mattered
The most useful finding for anyone formulating a product is the meta-regression. Higher daily doses of exogenous ketones were associated with bigger improvements in cognition. The review didn’t find statistically significant differences between supplement types, trial lengths, healthy vs. clinical populations, or whether people were under a stressor. With the trials available so far, those factors can’t be told apart.
Quality was decent, results were uneven
The average trial quality score was 7.9 out of 10 on the PEDro scale, which is respectable for supplement research. Individual results still varied a lot. One trial of AC-1204 (Henderson 2020), a caprylic triglyceride product, found no cognitive benefit in mild-to-moderate Alzheimer’s disease, and a 2019 ketone ester trial found no benefit in endurance-trained athletes. The authors concluded that larger, longer trials are needed to sort out dose, formulation and who benefits. The authors’ affiliations include the University of Hasselt, the Buck Institute for Research on Aging and Component Health Ltd., and I didn’t see a funding statement in the paper.
How big is the effect?
Pooled effect of exogenous ketones on cognition vs. common effect-size benchmarks (standardized mean difference).
Data: Bonnechère et al., Front Nutr 2026. Benchmarks are Cohen’s conventions. Bar width = value / 0.80.
Two Trials Worth Knowing
Ketones after mental fatigue
Quinones and colleagues (Nutrients, 2022) gave nine recreationally active men 25 g of a ketone monoester or a placebo, had them do a 40-minute Stroop task to wear them out mentally, then ran them through a 45-minute simulated soccer match. On a choice reaction test, the ketone group lost 1.3% of its accuracy vs. 3.4% on placebo (p = 0.02). Reaction time and Stroop scores didn’t differ. The study had no external funding, and the ester was supplied by TdeltaS Global. It’s a small ester study, but I like the design because it tests the situation most people care about: staying sharp when you’re already tired.
Accuracy lost after mental fatigue and exercise
Drop in choice reaction test accuracy, % (lower is better).
Data: Quinones et al., Nutrients 2022 (n = 9). Bar width = value / 3.4.
A BHB salt dose test in runners
Prins and colleagues (Nutrition & Metabolism, 2020) tested a BHB salt plus MCT supplement in 13 recreational male distance runners. One serving had about 7 g of racemic BHB salt and 7 g of MCT, and the high dose was two servings, taken 60 minutes before a 5 km time trial. The higher dose raised blood BHB more and did slightly better than the lower dose on one Stroop accuracy measure before the run, but most cognitive measures showed no treatment effect, and 5 km times didn’t change. The paper doesn’t state its funding source. I include it because it’s one of the few salt studies, and it shows how mixed the salt data is.
What This Means for goBHB Products
The review doesn’t single out any goBHB finished product, so I won’t pretend it tested one. What the review does support is that exogenous ketone supplements modestly improved cognitive test scores on average, and higher daily doses were associated with bigger improvements. This is how two products we supply line up.
MAC Energy
MAC Energy, Conor McGregor’s drink, has 2,000 mg of goBHB, 200 mg of caffeine from Purcaf® and 250 mg of Cognizin® citicoline in each 12 oz can. That’s a stacked approach: caffeine for alertness, plus goBHB. Our own cell-culture work on BHB and caffeine is covered in our caffeine crash study write-up; it’s unpublished in vitro work, not a human trial. You can read more about the formula in Inside MAC Energy.
CleanForm goBHB Energy Shot
If you want ketones without caffeine, CleanForm’s goBHB Energy Shot uses L-goBHB with zero caffeine and zero sugar in a 2 oz shot, sold in 6-packs in Blue Raspberry, Wild Berry and Sour Apple. It’s TruShield Certified, tested for more than 480 banned substances. Most of the human cognition data is on D-BHB, esters or D/L blends, so the L form is the least studied here; we cover the difference in L-BHB vs. D-BHB.
Safety notes: 200 mg of caffeine is a real dose, so skip MAC Energy if you’re under 18, caffeine-sensitive, pregnant, or already near your daily limit. BHB salts carry minerals, so count the sodium if you watch your blood pressure, and check with your doctor if you have kidney issues or take medication.
Where the Evidence Stands
My grade: a well-run 2026 meta-analysis of randomized trials says exogenous ketones produce a small, statistically significant improvement in cognitive test performance, and more ketones per day tends to mean more effect. The trials mix esters, salts and MCTs, so you can’t pull out a clean number for BHB salts. The salt-specific studies are few, small and mixed. None of these products are meant to treat or prevent any disease, and the clinical studies in the review describe research, not product uses. We’re planning a large trial comparing 2 g and 5 g doses of D-BHB and L-BHB against placebo on attention, memory and mood, and I’ll report what it finds either way.
FAQ
Do ketones improve focus and cognition?
On average, a little. A 2026 meta-analysis of 29 trial protocols found a small improvement in cognitive performance with exogenous ketones vs. placebo (SMD 0.29). Results varied a lot between individual studies.
Are BHB salts as good as ketone esters for the brain?
The review didn’t find a statistically significant difference by supplement type, though dose appeared to matter. There are far fewer cognition trials on salts, so we don’t know yet.
How much BHB do I need for mental performance?
There’s no established dose. The review linked higher daily doses to bigger effects, and studies used anything from single doses to daily protocols. Start with the label serving and see how you respond.
Can I take BHB with caffeine?
Many products combine them, including MAC Energy. Count your total caffeine for the day, and if you’re sensitive to it, a caffeine-free option like the CleanForm shot is the simpler choice.
The Bottom Line
The 2026 meta-analysis is the best summary we have on ketones and cognition, and it says the effect is modest, with higher daily doses associated with bigger effects. That’s a more useful finding than hype, because it tells you what to look for: enough ketones per serving, and realistic expectations. If you want the full list of products and doses, start with our 2026 goBHB products guide.
Sources: Bonnechère B, Stephens EB, Boileau AC, Ducker M, Stubbs BJ. The effect of exogenous ketone bodies on cognition across health and disease: a systematic review and meta-analysis. Front Nutr. 2026;13:1802531. Quinones MD, et al. Ketone Ester Supplementation Improves Some Aspects of Cognitive Function during a Simulated Soccer Match after Induced Mental Fatigue. Nutrients. 2022;14(20):4376. Prins PJ, et al. Dose response of a novel exogenous ketone supplement on physiological, perceptual and performance parameters. Nutr Metab. 2020. Product details from drinkmac.com and cleanformnutrition.com.