In a recent study published in the journal Scientific Reports, researchers explore the association between the consumption of spicy food and cognitive function related to Alzheimer’s disease (AD) patients with low physical activity.
Study: Spicy food intake predicts Alzheimer-related cognitive decline in older adults with low physical activity. Image Credit: New Africa / Shutterstock.com
Spicy food, physical activity, and cognition
Spicy food leads to a sensation of heat due to the stimulation of pain receptors on the tongue.
The link between certain tastes, cognitive decline, and AD has been widely studied. For example, one 15-year longitudinal population-based cohort study reported that consuming greater amounts of spicy food correlated with lower cognitive scores.
Similarly, numerous preclinical studies have demonstrated that increased capsaicin consumption can lead to denervation of the sensory nerves. Nevertheless, it remains unclear whether the consumption of spicy food is associated with cognitive decline or AD.
Physical activity has neuroprotective effects on the brain through different mechanisms. In one in vivo study on mice, researchers found that physical activity reduces excessive glutamate levels in the brain, thereby increasing mitochondrial glutamate oxidation and limiting its toxic effects. Furthermore, physical activity has been correlated with better cognitive function, reduced cognitive decline, as well as a lower incidence of dementia and AD.
About the study
The current study included 196 adults between 65 to 90 years of age without dementia, 113 of whom were cognitively normal (CN) and 83 with mild cognitive impairment (MCI). The study participants were recruited from a dementia screening program held at the memory clinic in Hallym University Dongtan Sacred Heart Hospital in Hwaseong, Republic of Korea.
The CN group included individuals with a Clinical Dementia Rating score of zero and were not diagnosed with dementia or MCI. Study participants diagnosed with MCI reported a Clinical Dementia Rating score of 0.5.
At least one of the four episodic memory tests in the Korean edition of the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) neuropsychological battery showed an age-, sex-, and education-adjusted z-score of less than one in the CN cohort. These included word list memory, word list recognition, word list recall, and constructional recall tests.
Researchers conducted systematic interviews with participants regarding their consumption of spicy foods. Participants who consumed spicy food at least once a week in the past year were asked to report the age at which they started eating spicy food and their preferred level of spiciness to evaluate the strength of their spicy food intake.
Trained researchers evaluated the potency of spicy foods using internationally recognized scales such as part-per-million (ppm) of capsaicin, Scoville heat units (SHU), and Gochujang hot taste units (GHU) for the spiciness of Korean gochujang or red chili paste.
The participants received clinical assessments from experienced psychiatrists using a standardized protocol that included the CERAD clinical and neuropsychological battery. Additionally, all study participants underwent a neuropsychological assessment protocol that included the CERAD neuropsychological battery, which was administered by trained neuropsychologists.
Researchers evaluated the cognitive domain connected to AD by assessing episodic memory, which is the earliest cognitive alteration noted in AD. Non-memory cognition was also evaluated for comparison.
Results
Ninety-three of the study participants belonged to the ‘not spicy’ group, 58 to ‘low spiciness,’ and 45 to ‘high spiciness.’ A significant difference in spiciness level was observed between groups based on their memory score.
No significant differences were found between groups in terms of spiciness level, regardless of age, sex, apolipoprotein E ε4 allele (APOE4)-positivity, education, clinical diagnosis, depression, vascular risk score (VRS), annual income, smoking, alcohol intake, physical activity, dietary styles, blood markers, or other cognitive performances.
The global cognitive score, as measured by total score (TS), varied significantly across different levels of spicy strength. Lower TS was significantly associated with high spiciness level, but not with low spiciness level.
A significant difference in memory scores was observed among the different levels of spicy strength; however, no significant difference in non-memory scores were correlated with spice intake. Lower memory scores were significantly associated with high spiciness levels, but not with low spiciness levels.
Physical activity was found to moderate the relationship between spicy food consumption and global and memory cognition, as indicated by the significant interaction between the two factors on memory and TS scores.
More specifically, a high spiciness level was linked to lower TS and memory scores in individuals with low physical activity. However, this association was not observed in those with high physical activity.
No significant statistical interactions were found between spicy level and age, APOE4-positivity, sex, VRS, and body mass index (BMI).
Conclusions
Consuming spicy food was linked to cognitive decline related to AD, specifically episodic memory, with this association influenced by the impact of physical activity. Thus, clinicians should monitor the intake of spicy foods and physical activity in older adults to prevent cognitive decline or AD.
Journal reference:
- Hwang, J., Choe, Y. M., Suh, G., et al. (2023). Spicy food intake predicts Alzheimer-related cognitive decline in older adults with low physical activity. Scientific Reports 13(1); 1-11. doi:10.1038/s41598-023-35234-0
