Carnosine supplementation improves delayed recall: a systematic review and meta‐analysis
Simon M Bell, Rohit Hariharan, Peter Laud, Arshad Majid, Barbora Courten- Psychiatry and Mental health
- Cellular and Molecular Neuroscience
- Geriatrics and Gerontology
- Neurology (clinical)
- Developmental Neuroscience
- Health Policy
- Epidemiology
Abstract
Background
Carnosine is a histidine‐containing dipeptide found in human muscle tissue and other organs like the brain. Data in rodents and humans indicate that administration of exogenous carnosine improved cognitive performance. However, RCTs results RCTs vary.
Methods
We searched OVID Medline, Medline, EBM Reviews, Embase, and Cumulative Index to Nursing and Allied Health Literature databases from 1/1/1965 to 1/6/2022 for all RCT of carnosine and other histidine‐containing dipeptides. 2653 abstracts were screened, identifying ninety‐four full‐text articles which were assessed for eligibility. 11 articles reporting use of carnosine supplementation were meta‐analysed. The random effects model has been applied using the DerSimonian‐Laird method.
Results
Carnosine treatment significantly increased performance on Wechsler Memory Scale (WMS) ‐2 Delayed recall (Z = 3.28, p<0.01). Treatment with carnosine had no effect on Alzheimer’s Disease Assessment Scale‐Cognitive (Weighted mean difference (WMD) (95% CI) = ‐0.2 (‐1.1, 0.7), P = 0.65, I2 = 0%), Mini‐Mental State Examination (WMD (95% CI) = 0.7 (‐0.2, 1.5), P = 0.14, I2 = 42%), The Wechsler Adult Intelligence Scale (WAIS) Digit span Backward (95% CI) = 0.1 (‐0.3, 0.5), P = 0.51, I2 = 0%), WAIS digit span Forward (WMD (95% CI) = 0.0 (‐0.3, 0.4), P = 0.85, I2 = 33%) and the WMS‐1 Immediate recall (WMD (95% CI) = 0.7 (‐0.2, 1.5), P = 0.11, I2 = 0%). The effect on delayed recall remained in subgroup meta‐analysis performed on studies of patients without mild cognitive impairment (MCI), and in those without MCI where average age in the study was above 65.
Conclusions
Carnosine supplementation improved scores on the Delayed recall examination, a neuropsychological test affected early in Alzheimer’s disease. Further studies are needed in people with early cognitive impairment with longer follow‐up duration and standardisation of carnosine doses to delineate the true effect.