Writing in The Journals of Gerontology: Series A, Chinese scientists report that older adults with higher intakes of dietary microbes from foods, including unpasteurized fermented foods, probiotic supplements, and unpeeled fresh fruits and vegetables, had significantly better cognitive scores across a range of tests, compared to people with the lowest intakes.
In addition, intake of prebiotic supplements was associated with better cognitive scores, compared to non-consumers of the supplements.
The study, which shows correlation and not causation, also noted that the potential brain health benefits were observed for people with diseases such as cardiovascular disease (prebiotics) and people with type-2 diabetes or hypertension (probiotics).
“While individual studies have examined the effects of prebiotics and probiotics on metabolism and behavior in mouse models of metabolic syndrome and chronic inflammation, there are relatively few studies that have investigated the association between live microbes, non-dietary prebiotic/probiotic, and cognitive function in humans, particularly across different disease subgroups and interactions,” wrote scientists from Shantou University Medical College in China.
“Our subgroup analysis suggests that the intake of live microbes may have a greater positive impact on cognitive function in older adults with specific disease states.”
Microbiota-gut-brain axis
The study adds to the ever-growing body of science supporting the role of the microbiota-gut-brain axis for cognitive function. The microbiota-gut-brain axis is a bidirectional interaction between the GI tract and the nervous system and implicates the ability of specific strains to produce key neurotransmitters like GABA (Gamma Aminobutyric Acid), serotonin and dopamine.
Consumer awareness of the axis is growing, with a 2021 survey by FMCG Gurus revealing that 45% of consumers associated probiotics with cognitive health.
Probiotic products on the market are already making stress or anxiety-related claims, with data from Lumina showing that the US is the leading market for such products, followed by Italy and then Australia.
Study details
The researchers used the NHANES 2011-2014, which provided data on 1,704 people with an average age of 69. The dataset also included results from three cognitive function tests: the Consortium to Establish a Registry for Alzheimer’s Disease Word Learning subtest (CERAD W-L, including immediate [CERAD-IRT] and delayed [CERAD-DRT] memory), the Animal Fluency Test (AFT), and the Digit Symbol Substitution Test (DSST).
The participants were divided into three groups, based on their estimated dietary live microbe intakes. These groups were previously defined by Marco et al. in The Journal of Nutrition (2022).
Correlating these intakes with the cognitive test scores showed that highest dietary live microbes group had significantly better cognitive function scores than people with the lowest intakes.
Similar results were obtained for non-dietary probiotic/prebiotic supplements, said the researchers.
“In this study, the rigorous quality control procedures employed by NHANES for data collection, along with its complex sampling design, enabled us to evaluate the association of the live microbes and non-dietary prebiotic/probiotic intake with cognitive function in a large representative sample of older adults in the United States,” stated the researchers.
"However, further longitudinal studies are required,” they concluded.
Recommended daily intake of dietary microbes
The study adds to the momentum behind attempts to achieve recommendations for daily intakes of dietary microbes from fermented foods. Such a recommendation may follow the already existing fiber daily intake recommendations.
Source: The Journals of Gerontology: Series A
Published online ahead of print, doi: 10.1093/gerona/glad175
“Association of Dietary Live Microbes and Non-Dietary Prebiotic/Probiotic Intake with Cognitive Function in Older Adults: Evidence from NHANES”
Authors: H. Tang, et al.