Healthy Adults vs Clinical Groups: Why Brain Supplement Results Do Not Transfer
Why a memory or focus result in one group, such as healthy adults, older adults, mild cognitive impairment or deficiency, cannot be assumed to apply to another.
Content last updated . This page has not been medically reviewed.
Why groups matter
Four things differ between groups.- Starting point. A group with a lack of a nutrient can change when the lack is corrected. A well-fed group has less room to change. The NCCIH digest says a multivitamin or high amounts of single vitamins "doesn’t have any clear benefits for cognition in well-nourished people". [1]
- Outcome. A trial may measure a lab task, a diagnosis of dementia, or daily function. These answer different questions, as the tests page explains.
- Time. Some trials last hours or weeks. Others follow people for years.
- Form and amount. An extract, a vitamin form and an amount each count as a separate test. Amounts below are study amounts, not advice.
What named studies found, by group
| Group studied | Study and amount (study amount only) | What it found | Label |
|---|---|---|---|
| Older adults with normal thinking or MCI (age 75 and over) | GEM trial: ginkgo extract, 120 mg twice a day, median follow-up 6.1 years; 3,069 volunteers, 2,587 with normal cognition and 482 with MCI [2] | Not effective in reducing dementia or Alzheimer's incidence overall, and no effect on progression to dementia in the MCI subgroup [2] | No good evidence of benefit |
| Adults 70 and over with memory complaints | GuidAge: ginkgo extract, 120 mg twice a day, up to 5 years [3] | Did not reduce the risk of progression to Alzheimer's disease compared with placebo [3] | No good evidence of benefit |
| Adults with amnestic MCI | Vitamin E, 2000 IU a day, for three years, against donepezil (a prescription medicine) and placebo [4] | "Vitamin E had no benefit in patients with mild cognitive impairment." [4] | No good evidence of benefit |
| People with MCI or Alzheimer's disease | Cochrane review of vitamin E (alpha-tocopherol), two trials usable [1] | No evidence it prevents progression to dementia in MCI [1] | No good evidence of benefit |
| Healthy adults under 60 | Systematic review of ginkgo extract trials [5] | No convincing evidence of a robust positive effect on any aspect of cognitive function [5] | No good evidence of benefit |
| Healthy adults, nine marketed ingredients | Systematic review [6] | Low certainty in the science; studies inconsistent, imprecise and often flawed [6] | Insufficient evidence |
| Older adults (average age 73) | COSMOS-Mind: a daily multivitamin-mineral, three years, telephone testing [7] | A small statistical benefit on a combined score. The authors say more work is needed in a more diverse group [7] | Promising but limited |
The multivitamin result shows how careful reading matters. COSMOS-Mind's cocoa extract showed no benefit. [7] The multivitamin result came from older adults, so it should not be carried over to students or to people with MCI. The National Institute on Aging (NIA) still says no vitamin or supplement is recommended for preventing Alzheimer’s or cognitive decline. [8] A separate analysis of a clinic subgroup of the wider COSMOS trial (adults aged 60 and over) found a modest benefit on global cognition over two years. [9] The full picture is on the multivitamin and memory trials page.
Deficiency is a different situation
Vitamin B12 or folate deficiency can cause problems with memory, understanding and judgement, and the NHS says some of those problems can be irreversible. [10] The NHS tells people who think they may have such a deficiency to see a GP. [10] Fixing a confirmed deficiency is medical care. It is not evidence that the same nutrient helps people who are not deficient. The vitamins and minerals for memory page goes deeper.Other groups
- Sleep-deprived people. One night of restricted sleep can worsen sustained attention in the lab. [11] A trial in that group answers a different question from a trial in rested people. See supplements for mental fatigue and sleep loss.
- People with ADHD. A separate group again. See supplements for ADHD.
- Repeated testing. In 29 healthy young adults, practice effects appeared on every task tested, so scores rose with repetition alone. [12]
Frequently asked questions
Can I use a result from a trial in healthy people if I have memory problems?
No. A result applies to the group studied. Memory problems can have treatable causes, and the NHS says to see a GP rather than self-diagnose. [13]
Did any large trial show a supplement prevents dementia?
Not among the trials named here. Ginkgo extract did not reduce dementia incidence in GEM or Alzheimer's progression in GuidAge, and vitamin E did not help in MCI. [2][3][4]
Why does a multivitamin trial in older adults not apply to students?
It tested older adults (average age 73), assessed by telephone over three years. [7] Nothing in it tests students, and the authors call for confirmation in more diverse groups. [7]
Does deficiency treatment count as a brain supplement?
No. Treating a confirmed deficiency is medical care, and some deficiency damage cannot be undone. [10]
Where can I learn how to talk about supplements with my clinician?
See talking with a health professional. The FDA advises talking to a doctor or pharmacist before using a supplement. [15]
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.
How to read the evidence labels
Labels used on this page: established role or deficiency treatment, evidence in adequately nourished people, promising but limited, no good evidence of benefit, insufficient evidence.
Safety and who should ask first
- Memory changes. The NHS says not to self-diagnose the cause of memory loss and to see a GP. [13] The NIA lists signs worth a doctor's visit, such as asking the same questions over and over. [14]
- Medicines. Some data suggest ginkgo can increase bleeding risk, and vitamin E supplements have the potential to interact with blood thinners such as anticoagulant and antiplatelet medicines. [1] Check medication interactions and tell your clinician and pharmacist about every supplement. Also see supplements before surgery.
- Pregnancy, breastfeeding, children, kidney or liver conditions. None of the studies described here was designed to answer these questions, so no result above applies to them. Ask a clinician or pharmacist. See pregnancy and breastfeeding.
- Product quality. The systematic review above notes that people do not always know what is in a supplement. [6] See quality testing.
References
- NCCIH Clinical Digest: Dietary Supplements and Cognitive Function, Dementia, and Alzheimer's Disease (July 2022). Read 2026-10-22.
- DeKosky et al. 2008, JAMA: Ginkgo biloba for prevention of dementia (GEM trial, PubMed). Read 2026-10-22.
- Vellas et al. 2012, Lancet Neurol: GuidAge ginkgo trial (PubMed). Read 2026-10-22.
- Petersen et al. 2005, N Engl J Med: Vitamin E and donepezil for mild cognitive impairment (PubMed). Read 2026-10-22.
- Canter and Ernst 2007, Hum Psychopharmacol: Ginkgo biloba in healthy people under 60 (PubMed). Read 2026-10-22.
- Crawford et al. 2021, J Altern Complement Med: Supplement ingredients and cognitive performance in healthy adults (PubMed). Read 2026-10-22.
- Baker et al. 2023, Alzheimers Dement: COSMOS-Mind cocoa extract and multivitamin trial (PubMed). Read 2026-10-22.
- NIA: Cognitive Health and Older Adults. Read 2026-10-22.
- Yeung et al. 2024, Am J Clin Nutr: Multivitamin-mineral and cognition, COSMOS-Clinic and meta-analysis (PubMed). Read 2026-10-22.
- NHS: Vitamin B12 or folate deficiency anaemia. Read 2026-10-22.
- Wüst et al. 2024, Sleep Med Rev: One night of sleep restriction, sleepiness and cognition (PubMed). Read 2026-10-22.
- Bell et al. 2018, Nutr Healthy Aging: Practice effects in nutrition intervention studies with repeated cognitive testing (PubMed). Read 2026-10-22.
- NHS: Memory loss (amnesia). Read 2026-10-22.
- NIA: Memory Problems, Forgetfulness, and Aging. Read 2026-10-22.
- FDA: Information for Consumers on Using Dietary Supplements. Read 2026-10-22.