In a groundbreaking 12-week trial, researchers discovered that a daily dose of fermented soy could sharpen memory in older adults, especially women over 70, hinting at a simple, diet-based way to support brain health with age.
Study: Effects of Fermented Soy on Cognition in Older Adults: Outcomes of a Randomized, Controlled Trial. Image credit: Garna Zarina/Shutterstock.com
A recent Nutrients study investigated the effects of fermented soy on cognitively healthy older adults. It found that fermented soy intake significantly improved memory in these adults.
Aging population and dementia
The increased life expectancy has contributed to an aging population, along with an overwhelming increase in dementia cases worldwide. A healthy diet and other lifestyle factors reduce the risk of cognitive decline.
Oxidative stress and neuroinflammation increase the risk of neuronal damage and age-related cognitive decline (ARCD). Several studies have highlighted the neuroprotective effects of plant-based foods due to the presence of high levels of antioxidants, n-3 polyunsaturated fatty acids, and anti-inflammatory phytonutrients, such as polyphenols. Phytonutrients reduce oxidative stress and neuroinflammation, promoting cognitive and cerebrovascular function.
Asian people commonly consume soy, which is rich in important secondary metabolites, such as phenolic flavonoids and isoflavones (daidzein and genistein). These metabolites possess antioxidant and estrogen-like properties, which benefit skeletal, cardiovascular, and cognitive health.
The available observational studies and clinical trials on soy and cognition in older adults have presented contradictory results, possibly due to the limited bioavailability of key isoflavones in their native glycoside forms. Previous studies have shown that fermented soy has an improved nutritional profile because, in this form, isoflavone glycosides are converted into aglycones, which are highly bioactive and are readily absorbed. Furthermore, fermentation enhances soy's antioxidant and anti-inflammatory properties, which are plausible mechanisms for improving its neuroprotective effects.
Most human-based research has assessed the cognitive benefits of fermented soy in people with mild cognitive impairment (MCI). For instance, a 12-week trial revealed the potential benefits of a probiotic fermented soybean powder on improving attention and memory composites. This treatment also enhanced brain-derived neurotrophic factor (BDNF) in older adults with MCI. Considering the benefits of fermented soy, it is essential to understand its effect on cognitively healthy older adults.
About the study
The current study performed a 12-week, triple-blind, placebo-controlled randomized controlled trial (RCT) to assess the cognitive effects of a non-probiotic, fermented soy product in cognitively healthy older adults. Healthy men and postmenopausal women 65 years and older were recruited from Loma Linda, USA. Any individuals with neurodegenerative disease and MCI, undergoing kidney dialysis and cancer treatment, and those who were intolerant or allergic to soy or dairy products were excluded.
Participants were advised to continue their usual physical activities, diet, and other lifestyle habits and refrain from taking any supplements that could affect cognition and immunity during the study period.
A total of 76 participants met the eligibility criteria, of whom 61 agreed to participate in this study. These candidates were randomized into either one of two groups: fermented soy (n = 33) and control (n = 28), stratified by sex. Household members were also randomized together into the same group. Participants consumed two pre-measured packets of Q-Can Plus® (fermented soy powder) or whey-based placebo powder each day for 12 weeks.
Q-Can Plus® is a non-probiotic fermented soy product, patented by BESO Biological Research Inc. The fermented soy powder contained 4.5g of fat, 8.4g of carbohydrates, 9.4g of protein, 5.6g of fiber, and 36.3mg of isoflavones per day. The placebo powder contained 15.6g of carbohydrate, 1.0g of fat, 8.5g of protein, 0g of fiber, and 0mg of isoflavones. Both fermented soy and placebo powders were flavored with cocoa and monk fruit sweetener.
Participants completed questionnaires on demographics, diet, stress, sleep, physical activity, and use of alcohol, tobacco, and caffeine. Participants’ height, body mass index (BMI), and body composition were measured at baseline. Every month, the participants met the study clinician and completed questionnaires about their experience with the intervention product. At baseline and after 12 weeks, all participants underwent a comprehensive battery of neuropsychological tests.
Study findings
The majority of the randomized participants were postmenopausal women 70 years and older. An individual assigned to the placebo group was removed because of a recent MCI diagnosis. The overall dropout rate was 22%, comprising five participants in the placebo group and eight in the fermented soy group. The reason for most dropouts was linked to the palatability of the intervention.
A total of 47 participants completed the study (fermented soy group: 25 and control: 22). The mean age of participants who completed the study was 74.0 years, and the mean age of participants who dropped out was 71.7 years. Interestingly, Hispanic participants exhibited a higher dropout rate compared to Whites and other racial groups.
The fermented soy and control groups did not significantly differ in participant characteristics or cognitive scores. Approximately 90% of participants adhered to the fermented soy and placebo interventions. After adjusting for baseline scores, the fermented soy group exhibited a modest yet statistically significant improvement limited to memory scores (p = 0.041) compared to the placebo group. No significant between-group differences were found in other cognitive domains or in overall global cognition.
Exploratory analyses revealed a more prominent effect among postmenopausal women who were 70 years and older. These post hoc analyses indicated that women in this subgroup experienced improvements in both memory and global cognition. However, the authors cautioned that these findings should be interpreted carefully due to the analyses' small sample size and exploratory nature. A mean improvement in memory scores of 8.47% was estimated for the fermented soy group, compared to 2.05% for the placebo group.
Conclusions
The current study suggests that fermented soy may support memory function in older adults. Modest improvements in memory, and exploratory evidence for global cognition, were observed among postmenopausal women 70 years and older. However, the authors emphasized that these results are hypothesis-generating and that causality cannot be inferred. Larger and longer-term studies are needed to confirm these preliminary findings.
Rather than recommending consumption outright, the researchers propose that fermented soy could be a promising dietary component to help maintain cognitive health and potentially delay cognitive decline when integrated into an overall healthy lifestyle.
Download your PDF copy now!
AI tool detects tiny brain lesions to improve epilepsy treatment in children