The Most Important Thing to Know
Sleep is the single most important factor for cognitive performance, followed by regular exercise. No supplement comes close to compensating for poor sleep or a sedentary lifestyle. If you're experiencing brain fog or difficulty focusing, the most productive first steps are optimizing sleep hygiene, increasing physical activity, and ruling out medical causes (thyroid dysfunction, depression, sleep apnea, nutrient deficiencies). Supplements are, at best, a distant third.
Evidence Summary
| Supplement | Evidence | Key Finding | Dosage |
|---|---|---|---|
| Creatine | Strong (cognitive) | SMD=0.29 overall; 0.88 in elderly aged 66-76 (p=0.009). No effect in young adults. 10 RCTs.[1] | 3-5g/day |
| Lion's Mane | Limited | MMSE +1.17 weighted mean increase. Improved depression, anxiety, sleep. 26 studies (5 RCTs).[2] | 0.5-3g/day |
| Citicoline | Limited | SMD 0.56-1.57 for cognition but poor study quality.[3] | 500-2000mg/day |
| Omega-3/DHA | Moderate | DHA important for brain structure; some evidence for cognitive maintenance in elderly.[4] | 1-2g/day |
| Caffeine + L-Theanine | Moderate | Combined improves attention and alertness. Caffeine is the main driver.[5] | 100mg caffeine + 200mg theanine |
| B12 | Insufficient | Only helps if deficient. No cognitive benefit in non-deficient.[6] | N/A |
| Ashwagandha | Limited | Small studies suggest improved reaction time and attention.[7] | 300-600mg/day |
Creatine: The Underappreciated Brain Supplement
Most people associate creatine with muscle and gym performance, but the brain is one of the most metabolically active organs in the body — and it relies heavily on the phosphocreatine energy system. A meta-analysis of 10 RCTs found creatine supplementation improved memory overall (SMD=0.29, p=0.02), but the standout finding was in older adults.[1]
In adults aged 66-76, the effect size jumped to SMD=0.88 (p=0.009) — a large and clinically meaningful improvement. By contrast, young adults showed essentially no benefit (SMD=0.03). This suggests creatine's cognitive benefits may be most relevant when the brain's energy metabolism is already declining with age.
Creatine has an excellent safety profile at 3-5g/day, is inexpensive, and has decades of research behind it. For older adults concerned about cognitive maintenance, it may be one of the more evidence-supported options available — though it's worth noting that even the strongest finding here comes from a relatively small number of studies, and more research in elderly populations specifically would strengthen the case.
Lion's Mane: Promising but Preliminary
Lion's mane (Hericium erinaceus) has generated significant interest for its potential neurotrophic properties — it contains compounds (hericenones and erinacines) that may stimulate nerve growth factor (NGF) synthesis. A 2025 review of 26 studies (including 5 RCTs) found supplementation was associated with a weighted mean MMSE increase of 1.17 points, along with improvements in depression, anxiety, and sleep quality.[2]
However, several important caveats apply. Most studies are small and short-term. The MMSE (Mini-Mental State Examination) is a screening tool, not a sensitive measure of cognitive enhancement in healthy people. Many studies used different preparations, dosages, and extraction methods, making comparisons difficult. And only 5 of the 26 studies were RCTs — the gold standard for establishing causation.
Lion's mane is likely safe at typical doses (0.5-3g/day), but the evidence is not yet strong enough to make confident claims about cognitive enhancement. It falls into the "interesting but needs more rigorous research" category.
Caffeine + L-Theanine: The Familiar Combination
The caffeine and L-theanine combination is one of the more studied "nootropic" pairings. Caffeine is well-established as a cognitive enhancer — it improves alertness, attention, and reaction time. L-theanine, an amino acid found in tea, is thought to smooth out caffeine's jittery effects while preserving its cognitive benefits.[5]
The honest assessment: caffeine is doing most of the work here. L-theanine may modestly reduce caffeine's anxiogenic effects, but the cognitive enhancement is primarily from caffeine itself. If you already drink coffee or tea, you're already getting this combination — a supplement is unlikely to add meaningful benefit.
What Doesn't Work for Brain
Vitamin B12 in non-deficient people. A meta-analysis of 18 articles (2,015 participants) found no significant effect of B vitamin supplementation on cognitive function or mood in people who weren't deficient.[6] B12 deficiency does cause cognitive symptoms — but if your levels are normal, supplementing more won't sharpen your thinking.
Most nootropic stacks. The supplement industry sells countless "brain formula" products combining 10-20 ingredients at sub-therapeutic doses. These products rarely have any clinical testing as a complete formulation. Individual ingredients may have some evidence at full doses, but combining small amounts of many compounds doesn't create a synergistic effect — it creates an untested, underdosed mixture. Be skeptical of any product claiming to be a comprehensive cognitive enhancer.
What to Consider
- Sleep is #1 for cognition. Even one night of poor sleep causes measurable cognitive decline. No supplement compensates for chronic sleep deprivation. If focus is your goal, start with optimizing sleep.
- Exercise is #2. Regular aerobic exercise has stronger evidence for long-term cognitive health than any supplement. It increases BDNF, improves cerebral blood flow, and reduces dementia risk.
- Supplements are a distant third. Even the strongest evidence here (creatine in elderly, SMD=0.88) is modest compared to the effects of sleep optimization and regular exercise.
- Creatine is the most evidence-supported option — particularly for adults over 60. At 3-5g/day with a strong safety profile and low cost, it's reasonable to consider for cognitive maintenance.
- Rule out deficiencies. If you're experiencing brain fog, check B12, iron, vitamin D, and thyroid levels before reaching for nootropics.
Frequently Asked Questions
Does creatine help brain function?
Yes, particularly in older adults. A meta-analysis of 10 RCTs found creatine improved memory overall (SMD=0.29), with a much larger effect in adults aged 66-76 (SMD=0.88, p=0.009). However, no significant effect was found in young adults. Creatine supports brain ATP levels during cognitive demand at a dose of 3-5g/day.
Is lion's mane good for focus?
The evidence is promising but still preliminary. A review of 26 studies (including 5 RCTs) found lion's mane improved MMSE scores by a weighted mean of 1.17 points and showed benefits for depression, anxiety, and sleep quality. However, most studies are small and short-term, and more rigorous trials are needed before strong conclusions can be drawn.
References
- Prokopidis K, et al. "Effects of creatine supplementation on memory in healthy individuals: a systematic review and meta-analysis of randomized controlled trials." Nutr Rev. 2023. 10 RCTs. PubMed
- Clinical review. "Hericium erinaceus (lion's mane) and cognitive function: systematic review." 2025. 26 studies (5 RCTs). PubMed
- Jasielski P, et al. "Citicoline for cognition: systematic review and meta-analysis." Nutrients. 2023. PubMed
- Dyall SC. "Long-chain omega-3 fatty acids and the brain: a review of the independent and shared effects of EPA, DPA and DHA." Front Aging Neurosci. 2015.
- Camfield DA, et al. "Acute effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood." Nutr Rev. 2014.
- Young LM, et al. "A systematic review and meta-analysis of B vitamin supplementation on depressive symptoms, anxiety, and stress." Nutrients. 2019. 18 articles, 2,015 participants. PubMed
- Choudhary D, et al. "A systematic review of the clinical use of Withania somnifera (Ashwagandha) to ameliorate cognitive dysfunction." J Diet Suppl. 2020. PubMed