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VITAMINS & SUPPLEMENTS · GUIDE

Nootropic Evidence by Outcome: Alertness, Attention, Memory, Mental Fatigue and Older-Adult Cognition

A plain overview of what reviews and trials found for alertness, attention, memory, mental fatigue, brain fog, ADHD and older-adult thinking, with links to a deeper page on each.

Content last updated . This page has not been medically reviewed.

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Quick answer
A useful question about any brain supplement is "for which outcome, in whom, compared with what?" This page sorts research by outcome instead of by product, and each outcome has a deeper page. A systematic review of nine ingredients marketed for thinking in healthy adults concluded that certainty was low, and that studies were "inconsistent and imprecise, and many are methodologically flawed." [1] The same review noted that people often cannot be sure what is in a supplement product. [1] This page is information only and is not medical advice.

How to read the labels in the tables: evidence in adequately nourished people means short-term trials in healthy people; promising but limited means some positive trials with small size, short length or high uncertainty; mixed means results point in different directions; insufficient evidence means too little or too weak to say. Where we looked and found nothing usable, we write "Proper evidence not found." Results do not transfer between groups: healthy young adults, older adults, people with mild cognitive impairment (MCI), dementia or ADHD are different questions. See why results do not transfer.

Alertness and attention in healthy adults

IngredientWhat the source foundLabel
CaffeineA meta-analysis of 31 trials (1,455 rested, healthy adults) found a small acute improvement in reaction time and accuracy. [2]Evidence in adequately nourished people (short term)
L-theanineA 31-trial meta-analysis found a single-dose improvement in choice reaction time and no significant effect on fatigue; one author founded a supplement company. [3]Promising but limited
BacopaA meta-analysis of nine trials reported a shorter choice reaction time. [4]Promising but limited
GinsengA 2024 meta-analysis found no positive effect on attention. [5]Insufficient evidence

Details: focus and concentration in healthy adults. Caffeine can also disturb sleep when taken too close to bedtime. [6]

Memory

IngredientWhat the source foundLabel
CreatineIn a meta-analysis, memory improved mainly in adults aged 66 to 76; the younger group (11 to 31 years) showed almost no difference. [7]Promising but limited
BacopaSix trials of 12 weeks: better free recall on 9 of 17 tests, little evidence for other abilities. [8]Promising but limited
AshwagandhaA 2026 meta-analysis of 20 trials (1,249 adults) reported better memory. [9]Promising but limited
Many over-the-counter ingredientsA review of common memory-product ingredients found no compelling evidence for several, mixed results for others. [10]Mixed

Details: memory in healthy adults.

Mental fatigue and sleep loss

Caffeine is the most studied option after sleep loss: a review of 45 publications concluded it is an effective counter-measure to the cognitive impairments linked with sleep loss. [11] Other ingredients have thinner evidence. Details: mental fatigue, alertness and sleep loss.

Brain fog

"Brain fog" is a description, not a diagnosis. NHS pages list it among the symptoms of long COVID and of menopause. [12][13] Proper evidence not found for a supplement shown to treat it in general; see brain fog and supplements and Brain Fog: Causes and When to Check.

Older-adult cognition and dementia

6 findings · 2 mixed · 4 limited or unclearThe colour follows the evidence label on each card.

  1. Ginkgo to prevent dementia

    Insufficient evidence

    In 3,069 adults aged 75 or older, ginkgo extract was not effective in reducing dementia or Alzheimer's incidence. [14]

  2. Ginkgo in MCI

    Insufficient evidence

    A 2026 Cochrane review: probably little or no effect at six months. [15]

  3. Omega-3 in healthy older people

    Insufficient evidence

    A Cochrane review found no benefit on thinking in cognitively healthy older people. [16]

  4. Vitamin E in MCI

    Insufficient evidence

    NCCIH's summary: no evidence it prevents progression to dementia. [17]

  5. Citicoline in older people with chronic brain conditions

    Mixed

    A 2005 Cochrane review: no benefit on attention, some evidence for memory and behavior, in short studies. [18]

  6. Supplements in Alzheimer's or MCI

    Mixed

    A 2026 network meta-analysis of 29 trials found gains on one scale and none on another (ADAS-Cog). [19]

The National Institute on Aging advises checking with a doctor before trying any pill or supplement that promises to prevent Alzheimer's. [20] Details for older adults: multivitamin trials such as COSMOS and ginkgo and large trials.

ADHD

ADHD is a medical condition. NCCIH states that conventional treatment is proven to reduce symptoms in most children and adults, and that many complementary-approach studies are mixed or have not shown improvement. [21] Supplements are not a replacement for assessment or treatment; see what trials found for ADHD and ADHD in adults.

Frequently asked questions

What is the best supplement for focus?

No supplement has been shown to be best. Caffeine has the most consistent short-term evidence for attention in rested healthy adults; others are less certain. [2][1]

What supplements help memory?

Creatine, bacopa and ashwagandha show promising but limited results on memory tests, and certainty is low. [7][8][9]

Do supplements help brain fog?

Proper evidence not found for brain fog in general. Brain fog has many possible causes, so a clinician is the right first step. [12][13]

Do supplements prevent dementia?

No supplement has been proven to. [20]

Do supplements treat ADHD?

NCCIH says results for complementary approaches are mixed or unproven, and that conventional treatment is proven to reduce symptoms in most people. [21]

More details: evidence, limits and cautions

The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.

Safety
Supplements can interact with medicines and with each other; read how interactions work and product quality. Ginkgo may raise bleeding risk, which matters before surgery. [17] A clinician or pharmacist can check a personal medicine list. For overall caution see safety and claim checks.
References
  1. Crawford C et al. J Altern Complement Med 2021. Dietary Supplement Ingredients for Optimizing Cognitive Performance Among Healthy Adults: A Systematic Review. Read 2026-10-23.
  2. Kløve K, Petersen A. Psychopharmacology 2025. A systematic review and meta-analysis of the acute effect of caffeine on attention. Read 2026-10-23.
  3. Gerolymos C et al. Mol Psychiatry 2026. Cognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials. Read 2026-10-23.
  4. Kongkeaw C et al. J Ethnopharmacol 2014. Meta-analysis of randomized controlled trials on cognitive effects of Bacopa monnieri extract. Read 2026-10-23.
  5. Zeng M et al. Phytother Res 2024. Effects of Ginseng on Cognitive Function: A Systematic Review and Meta-Analysis. Read 2026-10-23.
  6. Bagheri Davisaraei Y et al. Prog Brain Res 2024. Coffee and sleep: Benefits and risks. Read 2026-10-23.
  7. Prokopidis K et al. Nutr Rev 2023. Effects of creatine supplementation on memory in healthy individuals: a systematic review and meta-analysis of randomized controlled trials. Read 2026-10-23.
  8. Pase MP et al. J Altern Complement Med 2012. The cognitive-enhancing effects of Bacopa monnieri: a systematic review of randomized, controlled human clinical trials. Read 2026-10-23.
  9. Zhu X et al. Front Pharmacol 2026. Effects of Withania somnifera (L.) Dunal (Ashwagandha) on cognitive and physical function in adults. Read 2026-10-23.
  10. Hersant H et al. CNS Drugs 2023. Over the Counter Supplements for Memory: A Review of Available Evidence. Read 2026-10-23.
  11. Irwin C et al. Neurosci Biobehav Rev 2020. Effects of acute caffeine consumption following sleep loss on cognitive, physical, occupational and driving performance: A systematic review and meta-analysis. Read 2026-10-23.
  12. NHS (UK), Long-term effects of COVID-19 (long COVID) (page last reviewed 19 August 2025). Read 2026-10-23.
  13. NHS (UK), Menopause: symptoms (page last reviewed 19 May 2026). Read 2026-10-23.
  14. DeKosky ST et al. JAMA 2008 (Ginkgo Evaluation of Memory study). Ginkgo biloba for prevention of dementia: a randomized controlled trial. Read 2026-10-23.
  15. Wieland LS et al. Cochrane Database Syst Rev 2026. Ginkgo biloba for cognitive impairment and dementia. Read 2026-10-23.
  16. Sydenham E et al. Cochrane Database Syst Rev 2012. Omega 3 fatty acid for the prevention of cognitive decline and dementia. Read 2026-10-23.
  17. NCCIH, Dietary Supplements and Cognitive Function, Dementia, and Alzheimer's Disease: What the Science Says (July 2022; NCCIH Clinical Digest for health professionals). Read 2026-10-23.
  18. Fioravanti M, Yanagi M. Cochrane Database Syst Rev 2005. Cytidinediphosphocholine (CDP-choline) for cognitive and behavioural disturbances associated with chronic cerebral disorders in the elderly. Read 2026-10-23.
  19. Li Y et al. Nutr Neurosci 2026. The impact of supplements on cognitive function for Alzheimer's disease or mild cognitive impairment: a systematic review and network meta-analysis. Read 2026-10-23.
  20. National Institute on Aging, Preventing Alzheimer's Disease: What Do We Know? (content reviewed October 10, 2023). Read 2026-10-23.
  21. NCCIH, Attention-Deficit Hyperactivity Disorder at a Glance (page last updated May 2019). Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.