Study identifies top-performing natural extracts for improving cognitive function

A new study published in Frontiers in Pharmacology suggests that some natural plant extracts may help improve cognitive function in healthy adults. Using a comprehensive comparison of 27 randomized controlled trials, researchers found that certain herbal supplements were associated with better performance in memory, executive functioning, and cognitive flexibility.

Among the top performers were extracts from Polygala tenuifolia, and a combination of Cistanche tubulosa and Ginkgo biloba. While these findings are promising, the authors emphasize the need for more high-quality research to confirm these benefits.

The study was driven by the growing popularity of natural supplements for brain health and the increasing interest in strategies to delay cognitive decline. As people live longer, maintaining mental sharpness into older age has become a priority. However, despite the widespread use of herbal supplements marketed for “brain boosting,” there is little clarity on which ones—if any—are actually effective.

The authors aimed to address this gap by using a technique called network meta-analysis. This method allows researchers to compare the effectiveness of multiple treatments, even if those treatments were not directly compared in individual studies. This approach helps establish a ranking of different interventions based on available evidence. The team focused specifically on healthy adults, excluding studies on people with dementia or other cognitive disorders, to assess whether natural extracts can offer benefits before major decline occurs.

To gather relevant studies, the researchers searched four major scientific databases—PubMed, Embase, the Cochrane Library, and Web of Science—up to September 2024. They included only randomized controlled trials that tested the effects of natural extracts on cognitive function in adults without diagnosed cognitive impairment. Interventions had to last at least four weeks and include placebo-controlled comparisons. They focused on five cognitive domains: global cognition, memory, attention, executive function, and cognitive flexibility.

After screening more than 5,000 articles, the researchers identified 27 qualifying studies, representing 2,334 participants in total. These trials investigated 19 different natural extract treatments. Examples included Ginkgo biloba, Bacopa monnieri, blueberry-derived polyphenols, rosmarinic acid from rosemary, and less familiar combinations like Cistanche tubulosa plus Ginkgo biloba. Most studies used standard cognitive assessments such as the Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), and computerized tests to evaluate outcomes.

Each treatment was ranked using a statistical tool called SUCRA (Surface Under the Cumulative Ranking curve), which estimates the probability that a given treatment is the best among all those studied. This helped the researchers identify which natural extracts showed the most consistent effects across different cognitive measures.

The most striking result was that the root extract of Polygala tenuifolia (RPTW) had the highest ranking for improving overall cognitive function, with a SUCRA value of 95.9%. This plant has traditionally been used in East Asian medicine for its calming and memory-enhancing properties. Evidence suggests that it improves brain glucose metabolism, inhibits enzymes that break down acetylcholine (a neurotransmitter involved in learning and memory), and reduces inflammation and oxidative stress—factors often implicated in age-related cognitive decline.

The combination of Cistanche tubulosa and Ginkgo biloba (referred to as CG) was especially effective for improving specific cognitive domains. CG ranked first for memory (SUCRA: 89.3%), executive function (SUCRA: 96.9%), and cognitive flexibility (SUCRA: 98.0%). These findings are consistent with earlier work showing that Ginkgo biloba improves antioxidant activity in the brain and that Cistanche may promote the growth of neurons and protect against cellular damage.

Attention was the one area where none of the natural extracts consistently outperformed placebo across the board. However, a specific combination of Polygonum odoratum and Morus alba (known collectively as MP) at a higher dose (1500 mg) ranked highest for attention improvement. Quercetin, a key compound in MP, is known for its anti-inflammatory and antioxidant properties, which may help explain the benefits seen in some studies.

The study also assessed the quality of the included trials. While most had low risk of bias in randomization and performance blinding, some had limitations such as unclear reporting of allocation procedures or dropouts. The researchers conducted sensitivity analyses to ensure these issues did not significantly affect the results. They also used funnel plots to check for publication bias and found no strong evidence suggesting that positive findings were more likely to be published than negative ones.

Although the results are promising, the authors caution against drawing strong conclusions based on the current data alone. Many of the studies included were small, with relatively short follow-up periods. There was also significant variation in how cognitive function was measured across trials, which can make it harder to compare outcomes directly. While natural extracts are generally perceived as safe, the current analysis did not include detailed information on potential side effects, which remains an important consideration.

The authors recommend several directions for future research. Longer-term studies are needed to assess whether the cognitive benefits of these extracts are sustained over time. Researchers should also explore optimal dosing strategies and investigate whether certain groups—such as older adults or people at risk of cognitive decline—benefit more than others. Standardizing assessment tools across studies would also help strengthen the evidence base. In addition, future research should report any adverse effects in detail, as even natural substances can pose risks under some conditions or when taken with other medications.

The study, “Effects of natural extracts in cognitive function of healthy adults: a systematic review and network meta-analysis,” was authored by Zhi-yuan Wang, Ya-lu Deng, Ting-yuan Zhou, Yi Liu, and Yu Cao.