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Proprietary Spearmint Extract Improves Working Memory in Subjects with Age-associated Memory Impairment
ISSUE:
Page:
36-37

Reviewed: Herrlinger KA, Nieman KM, Sanoshy KD, et al. Spearmint extract improves working memory in men and women with age-associated memory impairment. J Altern Complement Med. 2018;24(1):37-47. doi: 10.1089/acm.2016.0379.

Age-associated memory impairment (AAMI) is a normal part of aging, but slowing this decline can improve quality of life. Spearmint (Mentha spicata, Lamiaceae) aerial parts contain polyphenols such as rosmarinic acid and salvianolic acid, which have been shown to have anticholinesterase, antioxidant, and anti-inflammatory activities in neuronal cells. The authors hypothesized that a spearmint extract with high levels of polyphenols could improve cognitive performance.

Using traditional breeding techniques, chemotypes of spearmint that produce significantly higher levels of bioactive polyphenols have been developed. A proprietary dried aqueous extract of these spearmint chemotypes has been shown to improve learning and memory in a mouse model of aging.1 Additionally, in an open-label 30-day study of healthy, older adults with self-reported memory impairment, the polyphenol-rich extract was well-tolerated and improved cognitive performance.2 The purpose of this randomized, double-blind, placebo-controlled study was to evaluate the effects of this proprietary spearmint extract on cognitive performance, sleep, and mood in healthy, older subjects with AAMI.

Healthy subjects (N = 90) aged 50-70 years were recruited from Addison, Illinois, from August 2013 through January 2014. They were assessed to have AAMI according to National Institute of Mental Health criteria (scores of ≥ 25 on the Memory Assessment Clinic Scale Questionnaire [MAC-Q], ≤ 29 on the Verbal Paired Associates [VPA] I and/or ≤ 9 on VPA II of the Wechsler Memory Scale IV, and ≥ 24 on the Mini-Mental State Exam [MMSE]). Included subjects had body mass indices between 18.5 and 35.0 kg/m2, had at least a high school diploma, were willing to maintain their habitual diet and exercise routines, and were willing to maintain consistent sleep duration the evening before study visits.

Subjects were excluded for the following reasons: had clinically significant abnormal laboratory test results; had a history or presence of cancer (except non-melanoma skin cancer), or clinically significant cardiac, renal, hepatic, endocrine, pulmonary, biliary, gastrointestinal, pancreatic, or neurological disorders; had a history of alcohol or substance abuse within the previous 12 months; had a history of depression within the past 24 months or used psychotropic medications within one month of screening; had a history of heavy smoking (more than one pack per day) within the past three months; had heavy caffeinated beverage consumption (more than 400 mg of caffeine per day) within the past two weeks; were pregnant, lactating, planning to become pregnant during the study period, or of childbearing potential and unwilling to use a medically approved form of contraception; had an occupation that resulted in disruption of sleep-wake cycles; used medications or supplements known to alter cognitive function within the past two weeks; or had an inability to complete or understand the cognitive function practice tests.

Subjects were randomly assigned to take a placebo (cellulose) or 600 mg/day or 900 mg/day spearmint extract for 90 days. The proprietary spearmint extract (Kemin Industries, Inc.; Des Moines, Iowa) contained ≥ 14.5% rosmarinic acid and 24% total polyphenols. Cognition was assessed on days 0, 45, and 90 with the Cognitive Drug Research (CDR) System, which is a validated computerized testing instrument. Mood was assessed with the Profile of Mood States (POMS) questionnaire on days 0 and 90. Sleep was assessed with the Leeds Sleep Evaluation Questionnaire (LSEQ) on days 0 and 90. Before and during all test visits, subjects were instructed to avoid vigorous physical activity for 24 hours, alcoholic beverages for 24 hours, caffeine for 10-14 hours, and tobacco (Nicotiana tabacum, Solanaceae) use for one hour.

Compliance was excellent (≥ 98.1% for all groups). One subject in the placebo group and two subjects in the 600-mg spearmint group discontinued the study due to adverse effects (AEs). Only one AE (heartburn) was considered probably related to the 600-mg spearmint treatment.

At 90 days, participants in the spearmint groups showed improvements in working memory and spatial working memory. (According to the authors, “Working memory pertains to the ability to use and manipulate information stored within short-term memory.” Spatial working memory is working memory of visuospatial information.) Comparisons between active groups showed that subjects taking 900 mg spearmint had a significantly greater improvement (22%) in quality of working memory compared with a 5% improvement in the 600-mg spearmint group (P = .021) and 7% improvement in the placebo group (P = .047). Subjects taking 900 mg spearmint also had a significantly greater improvement (17%) in spatial working memory compared with a 3% improvement in the 600-mg spearmint group (P = .017) and 6% improvement in the placebo group (P = .046). There were no other significant improvements in cognitive performance.

Of the seven mood factors assessed, there were significant overall treatment effects for the vigor-activity factor (P = .039) and the composite total mood disturbance (TMD) (P = .037) after 90 days of spearmint supplementation. However, comparisons between groups for the vigor-activity factor showed a trend toward significance only for the 900-mg group versus placebo (P = .065). Similarly, for the TMD, comparison showed a trend toward significance only for the 900-mg group versus placebo (P = .083). There were no significant improvements in the other mood factors.

Significant overall treatment effects also were observed in subjective ratings of ease of getting to sleep (P = .017) and behavior following wakefulness (P = .042) for subjects supplemented with spearmint. Comparisons indicated that the 900-mg spearmint group had significantly improved ability to get to sleep compared with placebo (P = .005). Comparisons also showed a significant improvement in behavior following wakefulness in the 900-mg versus the 600-mg group (P = .014) but not versus placebo (P value not reported). There were no significant differences among groups in quality of sleep or ease of awakening from sleep.

In summary, subjects with AAMI who took 900 mg per day of the proprietary spearmint extract had significantly improved working memory, spatial working memory, and self-reported ability to get to sleep after 90 days. (It was not discussed whether the odor of the test capsule was detectable, which could have impacted blinding.) There were overall spearmint treatment effects for vigor-activity, TMD, and behavior after waking, with trends toward statistical significance compared to placebo. Also, 900 mg per day spearmint for 90 days was well-tolerated in this population. This study bears repeating with a longer duration (age-related cognitive impairment increases over time) and with additional measures of cognitive function, preferably assessed at additional time points throughout the study.

—Heather S. Oliff, PhD

References

  1. Farr SA, Niehoff ML, Ceddia MA, et al. Effect of botanical extracts containing carnosic acid or rosmarinic acid on learning and memory in SAMP8 mice. Physiol Behav. 2016;165:328-338.
  2. Nieman KM, Sanoshy KD, Bresciani L, et al. Tolerance, bioavailability, and potential cognitive health implications of a distinct aqueous spearmint extract. Functional Foods in Health and Disease. 2015;5(5):165-187.