Cistanche tubulosa and Ginkgo Biloba Extracts: Evidence for Cognition and Memory

Human randomized controlled trials have evaluated whether Cistanche tubulosa extract combined with Ginkgo biloba extract can improve cognition or memory. However, the evidence remains preliminary and has not been independently replicated.

The main takeaways are:

• Two randomized, placebo-controlled trials directly evaluated cognition or memory, randomizing 100 participants and 117 participants, respectively.
• Both trials reported improvements in some cognitive or memory measures. The principal doses studied were:
• About 300 mg/day of Cistanche tubulosa extract
• About 120 mg/day of Ginkgo biloba extract
• Neither trial included a Cistanche-only group or a ginkgo-only group, so synergy between the two ingredients has not been demonstrated, and it is not possible to determine which ingredient produced the effect.
• Both trials were closely connected to researchers at Amway/Nutrilite, which developed the combination product. No fully independent team has yet replicated the findings.
• There is no evidence that the combination prevents Alzheimer’s disease, lowers dementia incidence, or reverses diagnosed dementia.

A more accurate conclusion is:

This specific standardized combination may improve some test scores in middle-aged and older adults over 30 to 90 days, but it cannot yet be considered a well-established cognitive treatment.

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1. Direct cognition trials of Cistanche plus ginkgo

Trial 1: 2024 cognition study in middle-aged and older adults

The title of the thesis is:

《A randomized, double-blind, placebo-controlled study of Cistanche tubulosa and Ginkgo biloba extracts for the improvement of cognitive function in middle-aged and elderly people》

It was published in Phytotherapy Research in August 2024.

Basic design

The registration information shows that the study plans to recruit 100 people, with 50 in each group. The MMSE of the enrolled individuals should range from 24 to 29 points. That is to say, not all of these people have been clinically diagnosed as having mild cognitive impairment, but they are more like middle-aged and elderly people with "low normal cognition or cognitive risk".

Cognitive scoring results

Ninety days later, the compound group reported:

The abstract of the paper states that these changes were not only significant within the compound group but also superior to those in the placebo group. Indicators such as long-term memory and delayed memory in Cognitrax and the revised Wechsler Memory Scale have also improved.

Blood marker results

The study also reported a decrease in the following indicators in the compound group:

• Total tau protein
• Phosphorylated tau: pT181, pS199, pT231, pS396
• Thyroid stimulating hormone (TSH

Triiodothyronine T3 and free T3 increased.

But this part must be understood with caution:

1. The tau index in peripheral blood can be affected by measurement methods, physiological fluctuations and various diseases.
2. Changes in blood indicators do not necessarily mean that the pathology of Alzheimer's disease in the brain has been reversed.
3. The study did not use amyloid PET, tau-PET or cerebrospinal fluid, etc. to confirm disease changes;
4. The study lasted only 90 days and did not observe the future incidence of dementia.

Therefore, these are more suitable to be regarded asExploratory biomarker resultsIt cannot be regarded as evidence of "clearing tau protein in the brain".

How large was the effect?

Statistically speaking, both MMSE and MoCA have achieved significant differences, but their clinical significance remains uncertain:

• The increase of 0.6 points in MMSE is relatively small and may also be partly influenced by repeated tests and learning effects.
• The increase of 1.9 points in MoCA is more worthy of attention, but it is still necessary to observe whether it has improved practical functions such as daily work, financial management, medication, and driving.
• The study did not report whether it remained effective after long-term discontinuation.
• The available summaries do not provide complete effect sizes, confidence intervals, and details of the final number of completers for all major indicators.

Conflicts of interest

The authors of the paper are affiliated with Amway Shanghai Innovation & Science Co., LTD., Amway China R&D Center, and two hospitals. The corresponding author is also from Amway. In other words, this was not an experiment completed entirely by an independent academic team.

This does not mean that the experiment is necessarily invalid, but it will reduce the certainty of the evidence, especially requiring an independent team to repeat it.

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Trial 2: 2026 memory and MRI study in healthy adults

The study was published in March 2026 Frontiers in PharmacologyThe title is:

《Cistanche tubulosa-Ginkgo biloba combination enhances memory via cortico-cerebellar reorganization: a randomized controlled trial》

Basic design

A total of 117 people were included in the intention-to-treat analysis; Two people in the placebo group withdrew due to personal reasons. Eventually, approximately 59 people in the compound group and 56 people in the placebo group completed the process.

Precise dosage

Each tablet contains:

• Cistanche tubulosa extract150 mg
• The standardized echinacoside content was at least 28%
• That is, each tablet contained at least 42 mg of echinacoside
• Ginkgo biloba extract60 mg
• The total flavonoid glycosides shall not be less than 25%
• Terpene lactones should be no less than 6%
• That is, each tablet should contain at least 15 mg of flavonol glycosides and 3.6 mg of terpene lactones

Two tablets per day, so the total daily dosage is:

Memory test results

The clinical memory scales adopted include:

• Pointing to memory
• Associative learning
• Free memory of images
• Meaningless graphic recognition
• Recall of portrait features
• Total score
• Memory quotient

The average change after 30 days is:

The compound group also showed better changes in total score and memory quotient than the placebo group. It is worth noting that the "meaningless graphic recognition" actually declined in both groups, but the decline in the compound group was even smaller. It cannot be simply described as an absolute improvement in this ability.

MRI result

Researchers reported in a 15-person MRI subgroup:

• Changes in gray matter volume in the auxiliary motor area and the central anterior gyrus;
• The low-frequency amplitude of the left cerebellar lobe VI increases;
• Some changes in brain images are correlated with changes in memory tests.

However, there were only 15 people in the MRI subgroup, among whom only 6 received placebos, which was far from sufficient to stably prove that "the compound reorganized the brain network". Whether the reduction in brain region volume represents neural efficiency, measurement fluctuations or other factors cannot be determined from this study either.

Therefore, the mechanistic conclusion in the title of the paper that "memory is enhanced through the recombination of the cortex and cerebellum" is significantly stronger than what the data itself can support.

Important methodological issues

This study was actually conducted from February 2019 to December 2020, but the Chinese clinical trial registration page shows that the registration version was established in May 2024, meaning it was registered several years after the completion of the study. Post hoc registration increases the risk of selective reporting of results, as it is impossible for the outside world to confirm which primary endpoints were pre-specified before the study began.

In addition, the study measured multiple cognitive sub-items, overall scores, age subgroups, and various MRI indicators, but the statistical methods in the paper did not clearly show that adequate corrections were made for all multiple comparisons. This will increase the probability of occasional significant results.

Conflicts of interest

The paper states that there is no external research funding support, but many authors were employed by Amway Shanghai or Amway China, and the trial product was also developed by Nutrilite Health Research.

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2. Supporting evidence: the 2021 chronic fatigue syndrome trial

This study is not a strict cognitive enhancement experiment, but it still utilized Cistanche+Ginkgo biloba.

Design and scale

The Cistanche extract is standardized to at least 28%echinacoside; Ginkgo biloba extract contains 24% total flavonoid glycosides.

Converted daily active ingredients:

Result

The overall symptom response rate is:

• Placebo: 27.6%
• Low dose: 72.4%
• High dose: 81.4%

The item of "impaired memory or attention" in the questionnaire has also improved.

However, this cannot be regarded as strong cognitive evidence because:

• Cognition is merely a subjective item in the fatigue questionnaire.
• There is no complete and objective memory or executive function test;
• The study population consists of patients with chronic fatigue.
• The author himself admits that it is impossible to determine whether the effect comes from Cistanche, ginkgo or a combination, nor can he estimate whether the combination is more effective than individual components.

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3. The most important limitations of the evidence

1. Synergy has not been demonstrated

To prove that the two have a synergistic effect, an ideal test should have four groups:

1. Cistanche for single use;
2. Ginkgo biloba for single use;
3. The two are combined;
4. Placebo.

At present, the main trials are only the "combination group" and the "placebo group". Therefore, it can only be proved that:

This compound as a whole may be effective.

Cannot prove:

The combination of Cistanche and Ginkgo biloba is stronger than taking each one separately.

The use of "potential synergy effect" in the paper is a hypothesis and not a conclusion that has been experimentally verified.

2. The total sample remains small

A total of 217 people were randomly selected from two direct cognitive trials, and the populations were different:

• One category is middle-aged and elderly people aged 40 to 75 with cognitive risk.
• One category is healthy adults aged 30 to 65.

Compared with the hundreds to thousands of people, multi-center repetitive studies usually required in drug research, the current scale is not large enough to rule out chance, center effects and researcher bias.

3. The trials were too short

The current direct evidence is only:

• 30 days;
• 90 days.

I don't know

• Whether it is still effective after taking it for half a year or one year;
• Whether the effect disappears after deactivation;
• Is it safe for long-term continuous use?
• Whether it can reduce the risk of mild cognitive impairment developing into dementia.

4. The studies used the same type of commercial formula

Both experiments used standardized extracts instead of common medicinal powder, decocted Cistanche or randomly purchased Ginkgo biloba powder.

Therefore, the result cannot be extrapolated to:

• Soak Cistanche slices in water;
• Ordinary Cistanche fan;
• Ginkgo biloba Tea
• Ginkgo biloba products without indicating the content of flavonoids and terpene lactones;
• Other Cistanche varieties;
• Health products with different extraction processes.

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4. Which Cistanche species was actually studied?

The research uses:

Cistanche tubulosa, Cistanche tubulosa

Rather than any Cistanche in a general sense.

Products available on the market may use:

• Cistanche tubulosa;"
• Desert Cistanche, Cistanche deserticola;
• Mixtures of different varieties;
• Raw medicinal material powder;
• Water extract;
• Extracts with different concentration ratios and echinacoside contents.

Study results should be compared mainly by the daily echinacoside dose, rather than simply by the number of milligrams of Cistanche listed on the package.

For example:

• Three hundred milligrams of an extract standardized to 28% echinacoside can provide at least 84 mg of echinacoside.
• A product of 500mg, containing only 10%echinacoside, is only available at 50mg.
• For 1000 mg of common Cistanche powder, without standardized content, it is completely impossible to confirm whether it is equivalent to the test dose.

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5. Ginkgo extract must also be standardized

The studies did not use raw ginkgo leaves; they used standardized Ginkgo biloba extract.

The core logo components include:

• Flavonol glycosides
• Terpene lactones, including ginkgolide and ginkgolide;
• At the same time, potentially harmful components such as ginkgolic acid should also be restricted.

The standard for Ginkgo biloba extract in the 2026 trial is:

• 120 mg per day;
• Total flavonoid glycosides ≥25%, that is, ≥30 mg;
• Terpene lactone ≥6%, that is, ≥7.2 mg.

This is similar to the 24% flavonoids and 6% terpene lactones commonly used in standardized ginkgo biloba extracts in Europe. However, just because the specifications are similar, it cannot be assumed that the quality and absorption of all ginkgo biloba products are exactly the same.

In particular, do not steep raw ginkgo leaves or consume crude ginkgo plant material on your own. The U.S. NCCIH notes that Ginkgo biloba extract is not equivalent to fresh ginkgo seeds or crude plant material. Fresh seeds are toxic, and roasted seeds have also caused serious adverse reactions.

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6. Interpreting the “effective dose” in current trials

Dose closest to the direct cognition evidence

The current scheme with the highest degree of repetition is:

• Cistanche tubulosa extract:300 mg per day
• echinacoside: Approximately 72 to 84 mg per day
• Ginkgo biloba extract120 mg per day
• Ginkgo biloba flavonol glycosides: approximately 27 to 30 mg per day
• Ginkgo terpene lactone: approximately 6.5-7.2 mg per day
• Take it in 1 to 2 doses
• It has been studied for 30 to 90 days

The "highest degree of repetition" here only indicates that two studies used similar formulas and does not mean that it has become a medically recommended dosage.

Would a higher dose be more effective?

Chronic fatigue tests have studied:

• Cistanche450 mg;
• Ginkgo 180 mg
• At least 126 mg of echinacoside should be used daily.
• Flavonol glycosides are approximately 43.2 mg.

The overall fatigue response rate in the high-dose group was slightly higher, but that was not a specific cognitive test and did not prove that high doses were significantly superior to low doses in terms of memory. Therefore, there is currently no sufficient reason to upgrade to a high dose merely for the sake of cognition.

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7. Safety

Findings observed in human trials

The 2024 Cognitive Experiment

No treatment-related adverse events were reported within 90 days, and blood and urine routine tests remained stable.

Cognitive Experiment in 2026

Neither group voluntarily reported any adverse events within 30 days, and no one withdrew due to discomfort.

Chronic fatigue test in 2021

Seven mild adverse events were reported, including:

• Upper respiratory tract infection
• Diarrhea
• Transient abnormal urea nitrogen;
• Elevated ALT or AST.

The researchers determined that these events were not related to the product and there were no serious adverse events.

However, neither the sample size nor the course of treatment was sufficient to rule out rare or long-term adverse reactions.

Main risks of ginkgo

The common adverse reactions listed by the NCCIH in the United States include:

• Dizziness;
• Gastrointestinal discomfort;
• Headache.

Ginkgo biloba may also increase the risk of bleeding in people using anticoagulants such as warfarin and may interact with other drugs. Pregnancy may increase the risk of premature birth or bleeding during delivery, and there is insufficient safety data during lactation.

The following situations are not recommended to take the medicine on your own without an assessment by a doctor or pharmacist:

• Warfarin is being used.
• Anticoagulant drugs such as apixaban, rivaroxaban and dabigatran are currently being used.
• Clopidogrel is currently in use;
• Long-term or high-dose use of aspirin, ibuprofen, etc.
• Have bleeding disorders, thrombocytopenia or recurrent gastrointestinal bleeding;
• I'm preparing for surgery or tooth extraction in the near future.
• Pregnancy or preparing for pregnancy;
• Have epilepsy or are taking antiepileptic drugs;
• Taking multiple chronic disease medications simultaneously.

Unknown risks of Cistanche

The human safety database of Cistanche is much smaller than that of Ginkgo. Existing studies can at most indicate that the overall tolerance of specific standardized extracts is acceptable within approximately 1 to 3 months, and cannot draw the conclusion of "long-term absolute safety" or "no drug interactions".

Especially for those with abnormal liver and kidney functions, those who have been taking medication for a long time, pregnant women and lactating women, there is currently a lack of sufficient research.

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8. The evidence for ginkgo used alone matters

The cognitive evidence for ginkgo itself is not stable.

NCCIH concluded that:

• Ginkgo has not yet been proven to prevent or delay dementia.
• In the GEM study involving over 3,000 people aged 75 and above, after an average of about 6 years of use, there was no difference in the incidence of dementia between the ginkgo group and the placebo group.
• For those already suffering from dementia, higher doses of standardized Ginkgo biloba extract may offer mild assistance in terms of symptoms, but the research results are inconsistent.
• The cognitive enhancement effect on healthy individuals remains uncertain, and many studies are of low quality.

This means that it cannot be inferred that Ginkgo +Cistanche can protect the brain or prevent Alzheimer's disease in the long term just because the short-term test of the compound is positive.

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9. Overall evidence rating