Partially-hydrolysed guar gum supplementation shown to improve visual memory in elderly – 12-week RCT

Visual memory assesses the extent to which individuals could accurately and swiftly memorise and re-recognise visual information.

Writing in Nutrients, ​researchers from Taiyo Kagaku, Kyoto Prefectural University of Medicine, and Medical Corporation Seishinkai said that improving visual memory was important because it was considered a critical function for elderly to live independently.

Improvements in this area could also prevent cognitive frailty in the elderly.  

“This capability is associated with the ability to remember seen information and recall it later, which is deeply involved in many aspects of daily life, such as remembering graphic instructions, navigating, operating machines, recalling images, and/or remember a calendar of events. ​

“These abilities are considered critical functions for individuals to live independently in their daily lives. The improvement of this function through the intake of PHGG is expected to contribute to the prevention of cognitive frailty in the elderly,” ​they said.

The 12-week randomised, double-blind, placebo-controlled, and parallel-group study was conducted between December 2022 and March 2023.

Sixty-six healthy elderly over 60 years old and with normal cognitive abilities were randomised to consume either five grams of PHGG or the placebo daily.

A water-soluble dietary fibre and also considered as a prebiotic, PHGG is derived from guar beans grown in arid regions, such as India and Pakistan.

Previous clinical trial findings published in 2023​ showed that taking five grams of PHGG daily was effective in enhancing gut health and promoting mental well-being, including improvements in aspects such as sleep and motivation.

The test materials, including the PHGG extract marketed as Sunfiber, were provided by Taiyo Kagaku which also funded the study.  

The participants’ cognitive functions, sleep quality, and subjective mood were evaluated at baseline and after 8 and 12 weeks of the trial.

Findings showed that at week 12, the intervention group had a significantly higher visual memory scores as compared to the placebo group.

For example, at week 12, their visual memory scores were 99.6 ± 15.8, improving by 3.1 ± 16.7 from the baseline. In contrast, that of the placebo had dropped from the baseline of 90.5 ± 15.4 by 2.7 ± 17.3.

During the test, the participants were initially presented with 15 types of figures on the screen. They were then required to identify the same figures from a new set of 15 types displayed subsequently.

The test evaluates how accurately and swiftly they can memorise and re-recognise visual information.

Higher scores indicate a better performance, with scores above 109 considered “above average”, 90–109 as “average”, 80–89 as “low average”, 70–79 as “below average”, and below 70 as “low”.

“Although the average values for both groups remained within the “average” range before and after the intervention, only in the PHGG group did the intervention bring the scores closer to the average for their age group, suggesting that the intake of PHGG improves visual memory,” ​said the researchers.

Sleep quality ​

Significant improvements in sleep quality were also observed in the intervention group.

Sleep quality is assessed using a questionnaire known as “Oguri–Shirakawa–Azumi Sleep Inventory, Middle-Aged version” (OSA-MA).

It is a four-step questionnaire comprising of 16 questions that are categorised into five subdomains, namely “sleepiness on rising”, “initiation and maintenance of sleep”, “frequent dreaming”, “refreshing”, and “sleep length”.

A higher score indicates a better sleep state.

In the intervention group, there was significant improvement from the baseline in their scores for “sleepiness on rising” and “initiation and maintenance of sleep”.

“Sleepiness on rising” also showing a significant improvement as compared to the placebo group. This is a composite measure that combines the scores for concentration, stress relief, mental clarity, and effortlessness.

For example, the intervention group’s “sleepiness on rising” scores at week eight were significantly higher than the placebo at 20.1 ± 4.4 versus 19.6 ± 6.0.

The intervention group also saw a significant increase in the “sleepiness on rising” scores by 1.8 ± 3.6, while that of the placebo had decreased by 0.6 ± 3.9 from baseline.

“It can be inferred that the consumption of PHGG resulted in an improvement in sleepiness on rising characterised by enhanced mental clarity, reduced stress levels, decreased irritability, and improved ability to concentrate,”​ said the researchers.

Japan’s ageing situation, rise in cognitive decline​

According to Japan’s Ministry of Internal Affairs and Communications Statistics Bureau, the country’s elderly population stood at 29.1 per cent as of September 2022.​

It is estimated that by 2025, approximately 20 per cent of the elderly population, or one in every five individuals, will develop dementia.

“Alongside this demographic trend, cognitive decline, primarily attributed to ageing, has emerged as a significant societal issue,”​ the researchers pointed out.

They said that while the detailed mechanisms behind the onset of cognitive decline remained unclear, some of the causes could include oxidative stress, inflammation, alterations in neurotransmitters, and phosphorylation of β-amyloid and tau proteins in the brain.

Obesity and lifestyle-related diseases could also raise the risk of developing dementia.

With greater knowledge on the gut-brain axis, the researchers said that pre/probiotics could play a role in influencing brain function.

“Intestinal bacteria produce various metabolites such as short-chain fatty acids (SCFAs), secondary bile acids, amino acid metabolites, and neurotransmitters, which can influence brain function through their effects on the nervous and immune systems.​

“Short-chain fatty acids are recognised as crucial factors in the gut–brain axis, suggesting that the improvements in sleep quality, vigour, and cognitive function associated with PHGG intake may be influenced by the promotion of intestinal SCFA production by PHGG.”​

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Source: Nutrients ​

Effectiveness of Partially Hydrolyzed Guar Gum on Cognitive Function and Sleep Efficiency in Healthy Elderly Subjects in a Randomized, Double-Blind, Placebo-Controlled, and Parallel-Group Study. ​

DOI: 10.3390/nu16081211.

Authors: Abe A, Kapoor MP, Morishima S, Ozeki M, Sato N, Takara T, Naito Y.