Cognitive decline is a well-established phenomenon associated with aging, with older adults often exhibiting lower cognitive performances compared to their younger counterparts . This decline can significantly impact daily behaviors, leading to difficulties in activities such as shopping, banking, and cooking .
Nutritional Impact on Cognitive Health
Dietary patterns, such as the Mediterranean diet, have been linked to positive effects on cognitive functions, including memory and global cognition . Furthermore, systematic reviews indicate that increased intake of vegetables and fruits contributes to improved cognitive and brain functions in healthy older adults .
Spices and Herbs as Cognitive Enhancers
Recent studies have shed light on the health benefits of spices and herbs, demonstrating their positive impact on cognitive functions [6,7,8]. Notably, the intake of ginger and garlic has been associated with improved cognitive functions in older adults, both with and without dementia [8,9]. Given their widespread use in daily dishes for flavoring, masking, and coloring, exploring the cognitive benefits of spices and herbs has become an area of considerable interest [10,11].
Wasabi and its Bioactive Compound
Wasabi (Eutrema japonicum), a traditional Japanese spice, has gained popularity not only for its unique flavor but also for its potential health benefits. The main bioactive compound in wasabi is Hexaraphane (6 methylsulfinyl hexyl isothiocyanate: 6-MSITC), belonging to the isothiocyanate family . Research has highlighted the antioxidant and anti-inflammatory functions of 6-MSITC [13,14], both of which are recognized as crucial for cognitive health in older adults [15,16,17,18].
Limited Studies on 6-MSITC and Cognitive Functions
While the health benefits of 6-MSITC have been explored, only two studies have investigated its effects on cognitive functions [19,20]. These studies focused on middle-aged adults, revealing improvements in executive functions and processing speed in those with subjective memory complaints and chronic fatigue syndrome, respectively [19,20].
Study Objectives and Hypotheses
To address the gap in knowledge regarding the impact of 6-MSITC on cognitive functions in healthy older adults, this study aims to investigate the cognitive benefits of 12 weeks of 6-MSITC intake. Three main hypotheses were formulated:
- Episodic and Working Memory Improvement: Based on a previous study reporting improved brain fog symptoms with 6-MSITC , it is hypothesized that 6-MSITC will enhance both episodic and working memory performances in older adults.
- Inhibition Performance Enhancement: Drawing from a study on middle-aged adults with subjective memory complaints , the hypothesis suggests that 6-MSITC intake will improve inhibition performances.
- Processing Speed Improvement: Considering the positive effects of 6-MSITC on processing speed in middle-aged patients with chronic fatigue  and the broader evidence from studies on Sulforaphane [22,23], it is hypothesized that 6-MSITC will enhance processing speed performances in healthy older adults.
This study aimed to investigate the potential cognitive benefits of a 12-week intervention with 6-MSITC in healthy older adults. The findings revealed significant improvements in working memory capacity and episodic memory performances, supporting the first hypothesis. However, contrary to the second hypothesis, no significant changes were observed in inhibition performances. Additionally, there were no significant alterations in processing speed, contrary to the third and fourth hypotheses.
Working Memory Enhancement
The positive impact of 6-MSITC on working memory capacity, measured by DS-B, aligns with prior research involving Sulforaphane . While previous studies demonstrated improvements in working memory with combined interventions , our study uniquely highlights the efficacy of 6-MSITC alone in enhancing working memory in healthy older adults.
Episodic Memory Improvement
The study revealed improvements in episodic memory performances, measured by LM and FSN, consistent with a previous study on middle-aged patients with chronic fatigue . This expands our understanding of 6-MSITC’s potential benefits by demonstrating enhanced verbal episodic memory and face-name association in healthy older adults. The implications suggest that 6-MSITC intake could effectively enhance daily memory functioning in the aging population.
Inhibition and Processing Speed Performances
Contrary to expectations, no significant changes were observed in inhibition and processing speed performances after 6-MSITC intake in older adults. These results differ from a previous study demonstrating a positive effect of 6-MSITC on inhibition performance . Methodological variations, such as intervention period, cognitive complaints, and participant age, may contribute to these inconsistencies. Further studies are warranted to elucidate the potential benefits of 6-MSITC on inhibition and processing speed performances.
Mechanisms Underlying Cognitive Improvement
To understand the mechanisms underlying memory improvements, it is essential to consider 6-MSITC’s anti-oxidant and anti-inflammatory functions [13,14]. Given the critical role of the hippocampus in working and episodic memory, we hypothesize that 6-MSITC may reduce oxidant and inflammatory levels in the hippocampus, thereby protecting against brain damage and enhancing neural functions. This, in turn, could lead to improved memory functioning in older adults.
Several limitations should be acknowledged. Firstly, the study did not measure biomarkers of anti-oxidants or anti-inflammatories, hindering a comprehensive understanding of the biological mechanisms. Future research should incorporate biomarker assessments. Secondly, the study exclusively focused on healthy older adults, necessitating further investigations to determine the generalizability of 6-MSITC’s cognitive benefits to young adults and individuals with cognitive impairments. Lastly, the sex distribution imbalance in the participant sample, while controlled for in analyses, highlights the need for future randomized controlled trials with a balanced sex ratio.
In conclusion, this study contributes valuable insights into the cognitive benefits of 6-MSITC in healthy older adults, emphasizing improvements in working and episodic memory functions. The findings suggest the potential of 6-MSITC as a nutritional intervention for enhancing cognitive health in aging populations. However, further research is essential to explore its impact on inhibition and processing speed and to unravel the underlying biological mechanisms.