Long-term consumption of virgin coconut (Cocos nucifera) oil diet impairs learning and memory in CD1 mice

OBJECTIVE: Virgin coconut oil (VCO) has been used in the management of dementia in Alzheimer’s disease (AD). Therefore, this research investigated the effect of long-term consumption of VCO diet on learning and memory in CD1 mice. METHODS: Thirty male CD1 mice (divided into three groups, n = 10) were fed with standard rodent chow (control), 5% and 20% VCO diets (respectively) for 28 d. The Morris Water Maze (MWM) test was used to test the effect of VCO on visuo-spatial learning and memory, while the Novel Object Recognition Test (NORT) was used to measure short- and long-term recognition memory. RESULTS: Learning performance of mice did not differ in the MWM. During the probe trial, duration in the retention quadrant and annulus crossings were lower (P < 0.05) in the 5% and 20% VCO diet groups compared to the control diet group, showing that VCO impaired visuo-spatial memory. During the NORT, mice showed more total approaches in the 20% VCO diet group (P < 0.05) compared to control and the 5% VCO diet groups during the short-term memory test. During the long-term memory retention test, the total approaches were also higher in the 20% VCO group compared to control and 5% VCO group (P > 0.05). The discrimination index was also lower in the 20% VCO group compared to control and 5% VCO diet groups indicating impaired long-term cognitive memory in mice given 20% VCO diet. Histological examination of brains showed damage within the CA1 pyramidal cell layer of the hippocampus in the 20% VCO diet group, in line with the behavioural observations. CONCLUSION: Long-term consumption of virgin coconut oil diet impairs memory in mice.