Snow fungus (TF; Tremella fuciformis, Tremellaceae) is a mushroom with a long history of use in traditional Chinese medicine. It is used for enhancing cognition, promoting healthy brain aging, and preventing neurodegenerative disorders. The bioactive polysaccharides in TF have demonstrated antioxidant, anti-inflammatory, immunomodulating, lipid-lowering, and hypoglycemic effects. According to the authors, TF has not been studied clinically for improving cognition. Subjective cognitive impairment (SCI) is defined as having a self-perceived cognitive problem, despite cognitive test measurements within a normal range. This population is thought to be a target for early intervention to prevent future development of neurodegenerative disorders including Alzheimer’s disease. The authors conducted a randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of oral TF in participants with SCI.
Participants (n=75, aged 40-65 years) were recruited through local advertisements in Seoul, Korea. Included participants had ≥12 years of education and SCI, but no clinical impairments (confirmed with physical and neurological examinations and blood tests). Excluded participants had suspected or diagnosed with mild cognitive impairment (MCI) with a Mini-Mental Status Examination (MMSE) score ≤24 or Clinical Dementia Rating Scale ≥0.5; axis I mental disorders; lifetime substance use; severe major illness that required treatment; history of loss of consciousness or seizure caused by head trauma; use of central nervous system medications within the last three months; intelligence quotient ≤ 80; or contraindications to magnetic resonance imaging (MRI). Participants received either 600 mg daily of TF (low dose), 1200 mg daily of TF (high dose), or placebo daily for eight weeks. The manufacturer or brand of TF was not reported. The participants were told to discontinue any nutritional supplements.
The primary outcome measured was changed in the Subjective Memory Complaints Questionnaire (SMCQ) score, which measures self-reported cognitive impairment and is a validated questionnaire for SCI. The secondary outcomes measured were (1) changes in performance on the Cambridge Neuropsychological Test Automated Battery (CANTAB) which assesses short-term memory; (2) changes in performance on the Wisconsin Card Sorting Test (WCST) which assesses executive function; and (3) changes in gray matter brain volume assessed via MRI. Safety and tolerability were measured with the Udvalg for Kliniske Undersogelser (UKU) Side Effect Rating Scale. Adverse events (AEs) were collected. Blood was collected for routine laboratory examinations. Assessments were made at baseline, week four, and week eight.
A total of 69 participants completed the study. There was no difference among groups in completion rates. Demographics and baseline measures were similar among groups. The compliance rate was high (>90%) and not significantly different between groups. On the SMCQ, the low dose TF group had a significant 3.97% improvement and the high dose TF group had a significant 9.18% improvement compared with placebo which had a 1.02% worsening (P=0.002 and P=0.007, respectively). On the CANTAB, both the low dose and high dose TF groups had a significant improvement compared with placebo (P=0.001 for both). On the WCST, only the high dose TF group had a significant improvement compared with placebo (P=0.02). There were no significant differences between the low and high dose TF groups in the rate of cognitive improvement on the CANTAB or WCST. Both the low and high dose TF groups had significant increases in gray matter volume in all clusters measured compared with placebo (P<0.05 for both). There was a significant correlation between TF intake and an increase in gray matter volume in the dorsolateral prefrontal cluster (P=0.02). The frequency of AEs was similar among groups. There were no serious AEs. The most frequently reported AE in the TF groups was weight gain, but there was no significant difference among groups on body mass index. The laboratory values were similar among groups.
The authors conclude that oral TF improved subjective memory complaints and cognitive performance (short-term memory and executive performance) in participants with SCI and was associated with increased gray matter volume. These findings support previous nonclinical research and traditional uses of TF. The authors hypothesize TF-induced improvements in cognition will improve quality-of-life. The safety of TF is supported by its use as a commonly consumed food in East Asia, but the authors acknowledge that additional studies are needed to confirm its safety. A limitation of the study is that they did not report the product used so an exact replication of the study will be difficult.
These findings of efficacy will require substantial confirmation. The authors report no conflicts of interest.
Ban S, Lee SL, Jeong HS, et al. Efficacy and safety of Tremella fuciformis in individuals with subjective cognitive impairment: a randomized controlled trial. J Med Food. April 2018;21(4):400-407. doi: 10.1089/jmf.2017.4063.