Shahar S, Aziz AF, Ismail SNA, et al. The effect of Polygonum minus extract on cognitive and psychosocial parameters according to mood status among middle-aged women: a randomized, double-blind, placebo-controlled study. Clin Interv Aging. 2015;10:1505-1520.
In Malaysia, Polygonum minus (a synonym of Persicaria minor, Polygonaceae) leaf is commonly referred to as kesum. Kesum is rich in antioxidant compounds which have been reported to improve psychological well-being and cognitive function. A 2013 investigation of a combination product containing kesum found significant improvements in cognitive performance and mood; however, the psychological benefits of kesum alone have not been evaluated. Hence, the purpose of this randomized, placebo-controlled study was to evaluate the effect of kesum on cognitive function and psychosocial parameters in healthy, middle-aged, working women.
Healthy women (n=35; aged 35-55 years) with a body mass index of < 40 kg/m2 were recruited from 3 schools and a "governmental organization" in Klang Valley, central Malaysia. Excluded subjects had medical conditions (e.g., uncontrolled diabetes and kidney problems); a history of substance abuse, alcohol abuse, smoking, major depression, or bipolar disorder; or were pregnant or breastfeeding.
Subjects were randomly assigned to receive either placebo (100 mg maltodextrin) or 500 mg kesum (LineMinus™; Biotropics Malaysia Berhad; Selangor, Malaysia) daily for 6 weeks. The extract was "standardized based on quercetin 3-glucuronide [0.4%] and quercitrin [0.01%]…. The standardized extract was prepared by a water extraction with dried leaves of PM [Polygonum minus] to plant extract ratio (1:20)…."
The following neuropsychological tests were conducted at baseline, week 3, and week 6: Digit Span, Rey Auditory Verbal Learning Test (RAVLT), Comprehensive Trail-Making Test (CTMT), Wechsler Abbreviated Scale of Intelligence (WASI), and CNS Vital Sign (CNSVS). At baseline, week 3, and week 6, the Profile of Mood States (POMS) and 36-Item Short Form Health Survey (SF-36) questionnaires were completed. Blood was drawn at baseline and week 6 to evaluate serum glucose, lipid, renal function, and liver function biomarkers. Blood pressure and body weight were measured at baseline and week 6. Subjects received daily phone calls or messages to remind them to take their medication. Compliance was assessed by pill counts.
Sociodemographic profile and cognitive and psychological status were similar between groups at baseline. Of the 63 subjects screened, 43 were randomly assigned to treatment (n=22 in the placebo group and n=21 in the kesum group). One subject in each group was lost to follow-up, and 1 subject in the placebo group and 2 subjects in the kesum group withdrew due to health problems; therefore, 38 subjects completed the trial (n=20 in the placebo group and n=18 in the kesum group). The authors do not explain the exclusion of 2 Chinese subjects in the placebo group and 1 male subject in the kesum group from the data analysis.
In subjects with mood disturbances (POMS > 15; n=7 in the placebo group and n=13 in the kesum group), kesum had a significant treatment effect on mean Digit Span score (P=0.037) and percent change in mean Digit Span score (P=0.014) compared to placebo. In subjects with mood disturbances, the kesum group had a significant improvement over the placebo group in the social functioning domain of the SF-36 (P=0.024). Also in subjects with mood disturbances, there was a significant improvement in the POMS vigor domain in the placebo group compared with the kesum group (P=0.027).
In subjects without mood disturbances (POMS ≤ 15; n=11 in the placebo group and n=4 in the kesum group), kesum had a significant treatment effect on WASI verbal IQ score (P=0.016) and WASI full IQ score (P=0.004).
There were no significant changes in the scores for the other POMS domains, RAVLT, CTMT, or CNSVS test. There were no significant changes in liver function, kidney function, or other blood indices. Compliance was excellent (98.3%).
The authors conclude that kesum improved attention, short-term memory (Digit Span test), and quality of life for social functioning among middle-aged Malaysian women with disturbed mood, and improved verbal IQ and full IQ among women without mood disturbances. Kesum supplementation at a dose of 500 mg daily "is safe to be consumed for 6 weeks, with potential benefits to attention, short-term memory, improved quality of life, and mood, as well as IQ," the authors write. The authors did not discuss the fact that the initial improvements observed at week 3 did not increase (Digit Span, social functioning) or had declined slightly at week 6 (verbal IQ, full IQ). It is possible that the dose of kesum was not appropriate (the dose was extrapolated from safety data in rats). Future studies should include multiple doses, a larger population, and a longer treatment duration.
This study was limited by the small sample size and the significant imbalance in the number of subjects in the subgroups (mood disturbances and without mood disturbances). It was significantly underpowered to detect genuine treatment effects, and therefore, the results should be interpreted with caution. The quality of the reporting was very poor. The description of the results lacked clarity and included several numerical and grammatical errors. The blinding also seems to be questionable. The study was funded by Biotropics Malaysia Berhad, the manufacturer of the test product.—Heather S. Oliff, PhD