Additionally, when the established dietary patterns were applied to a further cohort of Japanese older adults, it was observed that cognition function was significantly impaired in the HC pattern in both the healthy and those with cognitive decline.
“These findings suggest that a balanced dietary pattern rich in protein, including legumes, meat, seafood, eggs, and vegetables, is beneficial for good cognitive function in Japanese older adults,” the researchers highlight.
“We created a model that classifies dietary patterns according to the intake of seven food groups, and observed differences in cognitive function between dietary patterns, suggesting that simply examining the intake of certain foods may be used to predict cognitive decline in older adults.”
Dementia is a highly prevalent disease of the modern day, mirroring a growing aging population. It has been recognised as the seventh leading cause of death worldwide in 2022, highlighting the significant socio-economic burden the disease poses.
With a lack of treatment to halt or reverse its progress, there has been substantial interest in the role of nutrition in its prevention, due to its established vital role in cognitive function. With the disease typically developing after the onset of mild cognitive impairment (MCI), this is highlighted as an important stage to target.
Nutrients such as unsaturated fatty acids, polyphenols, caffeine, and some probiotics have been noted to have beneficial effects on cognition, yet the importance of nutritional synergies have been recently emphasised. Therefore, the focus has shifted to encouraging rich nutritional diversity.
Dietary patterns such as the Mediterranean-DASH intervention of Neurodegenerative Delay (MIND) diet have been proposed as a significant potential intervention to slow cognitive decline. Yet, due to the MIND diet being developed in reference to western diets, a barrier to achieving established guidelines lies in the variation of dietary habits resulting from cultural differences, such as in Eastern countries like Japan. Therefore, there is a need to establish these variations and tailor dietary pattern interventions so that they are appropriate and effective for different populations.
Thus, the researchers sought to identify the dietary patterns of elderly Japanese individuals and observe their relationship with cognitive function. The behaviours were then modelled on a further Japanese cohort, to investigate whether dietary differences could predict cognitive decline.
The researchers recruited 150 adults aged 65 and over from Kashiwa city, Japan, to model the dietary pattern of the elderly Japanese population. Dietary patterns were established following cluster analysis of dietary patterns, collated using self-administered diet history questionnaires. Cognitive function was then measured using the Montreal Cognitive Assessment.
The dietary patterns identified included a high-carbohydrate (HC) diet, with high cereal intakes, and a protein-balanced (PB) diet, following high intakes of legumes, vegetables, eggs, meat, and seafood.
The researchers observed that scores for cognition were significantly higher in the PB group than the HC group. Furthermore, following the application of the classification model to a new cohort of elderly Japanese adults, scores for cognition were found to be significantly higher in the PB group.
The researchers stress, “this study has made a significant contribution to the goal of establishing a diet that reduces cognitive decline suitable for the elderly Japanese by demonstrating dietary patterns associated with cognitive function in the elderly Japanese.”
The study further emphasises the power of nutrition as a tool for AD prevention, particularly highlighting the importance of protein intake. It is highlighted that the legumes consumed by the studied cohort mostly consisted of soy products, which mirrors previous studies that suggest soy isoflavones may have neuroprotective effects. In addition, the high contents of carotenoids, flavonoids, and vitamin E in green leafy vegetables, as well as the rich PUFA content of fish, have also been shown to reduce cognitive decline.
With regards to the HC findings, the researchers explain: “Carbohydrates have a much greater effect on insulin secretion than proteins or fats, and low carbohydrate diets are effective in reducing weight loss, reducing risk factors for cardiovascular disease, and improving type 2 diabetes. Hyperinsulinemia and diabetes are significant risk factors for AD.”
The report concludes: “We are currently planning an intervention study to shift older adults with HC patterns to PB patterns to prove the causal relationship between dietary patterns and cognitive function found in this study. Validation with larger sample sizes and additional research on the role of individual nutrients is needed to establish a standard diet therapy for dementia in elderly Japanese individuals.”
“Protein-Balanced Dietary Habits Benefit Cognitive Function in Japanese Older Adults"
by Keisuke Sakurai, Erika Okada, Saya Anzai, Risako Tamura, Izumi Shiraishi, Noriko Inamura, Satoru Kobayashi, Mikako Sato, Takashi Matsumoto, Kazuyuki Kudo, Yukihiro Sugawara and Tatsuhiro Hisatsune