"Clinically studied ingredients" can mean an eighteen-month randomised trial or a cell-culture study from decades ago. This page states, for each ingredient with published human research, exactly what was tested — dose, duration, who took part and what was measured.
Ginkgo Biloba — Free Recall, Six Weeks
Design: placebo-controlled and randomised, reported in Phytomedicine in 2011.
Who took part: 188 healthy volunteers, ages 45 through 56.
What they took: 240 mg of standardised extract each day for six weeks.
What came out: participants recalled more of their appointments without being prompted — p=0.038 immediately, p=0.008 after a delay. A separate recognition task involving a driving route showed no such advantage.
We include that second finding deliberately. The effect landed on unprompted retrieval and nowhere else, and a result with visible boundaries is more credible than one without.
Source: Kaschel R. Phytomedicine 2011 (PMID 21802920)
Lutein and Zeaxanthin — Attention, Twelve Months
Design: double-masked and placebo-controlled, published in Frontiers in Aging Neuroscience in 2017.
Who took part: 51 older adults living independently, averaging 73.7 years.
What they took: 12 mg of lutein and zeaxanthin together, daily, across twelve months.
What came out: macular pigment density rose measurably (p<0.03), and so did performance on complex attention (p<0.02) and cognitive flexibility (p<0.04). The authors' verdict was that supplementation "improved cognitive function in community-dwelling, older men and women."
Source: Hammond BR Jr et al. Front Aging Neurosci 2017;9:254
Curcumin — Memory and Attention, Eighteen Months
Design: double-blind and placebo-controlled, run at UCLA and reported in the American Journal of Geriatric Psychiatry in 2018.
Who took part: 40 adults between 51 and 84, none with a dementia diagnosis.
What they took: 90 mg of bioavailable curcumin, twice a day, for a year and a half.
What came out: the team concluded that daily curcumin "may lead to improved memory and attention in nondemented adults." PET scans pointed the same way, with shifts in areas governing mood and memory.
Two things sit side by side here. Eighteen months is far longer than most supplement studies manage, which strengthens it. Forty participants is a small group, which limits it.
Source: Small GW et al. Am J Geriatr Psychiatry 2018
L-Theanine — Reaction Time and Accuracy
Design: double-blind crossover, placebo-controlled, in Biological Psychology, 2008.
What was compared: L-theanine on its own, caffeine on its own, and the two in combination — which is how they already occur in a tea leaf.
What came out: the pairing quickened simple reaction time and numeric working-memory responses, lifted sentence-verification accuracy, and left participants reporting less fatigue. Theanine by itself fared worse on several measures, which is precisely why the natural combination is the one worth noting.
Source: Haskell CF et al. Biol Psychol 2008 (PMID 18006208)
Bamboo Extract and D-Glucosamine
No section, because we found no comparable human cognitive trials for either, and writing a paragraph of mechanism to fill the gap would defeat the purpose of this page. Bamboo Extract is a rich plant source of silica; D-Glucosamine is a naturally occurring amino sugar best known in joint nutrition. Both are reasonable inclusions. Neither is a memory ingredient.
How to Check Any Supplement's Research Page
- Does the dose match? A trial using 240 mg says little about a product containing 20 mg.
- Does the population match? Results in people with a diagnosis do not transfer to healthy adults, or the reverse.
- How long did it run? A six-week benefit is not evidence of a three-day benefit.
- Was it human research? Cell and rodent findings are a starting point, not an outcome.
- Was the finished product tested? Usually not. Pages that blur this are telling you something.
Apply all five here as readily as anywhere else. That is why the numbers are on the page.