Over the past decade, research has reported that diet and gut health could affect anxiety symptoms through changes in the intestinal microbiota.
To examine the effect of prebiotic and probiotic foods consumption on anxiety, a nationwide population-based cohort study was conducted by Korean researchers.
The study was supported by a grant funded by the country’s Ministry of Health and Welfare.
Data sets from the Korean National Health and Nutrition Examination Survey (KNHANES VII-3, 2019-2021) were analysed. A total of 4,317 individuals aged between 19 and 64 years were included.
A food frequency questionnaire was used to evaluate prebiotic and probiotic food consumption.
Prebiotic foods comprised fruits (excluding jams, sweetened fruits and juices) and raw vegetables, while probiotic foods included fermented vegetables such as pickles, kimchi, and sauerkraut.
Participants were divided into three groups according to the reported frequency of consuming prebiotic and probiotic foods — Q1 being the lowest tertile, Q2 the middle tertile, Q3 the highest tertile.
The severity of anxiety symptoms was assessed by the Generalized Anxiety Disorder 7-item (GAD-7) scale. Total scores range from 8 to 40, with higher scores indicating higher levels of anxiety. Scores of 10 and 15 or greater suggest moderate and severe anxiety respectively.
Based on their total GAD-7 scores, the participants were classified into either the high anxiety (HA) group (15%) or the low anxiety (LA) group (85%).
Those in the HA group were significantly younger, with an average age of 49.2 years, and included 432 females (66.9%) and 214 males (33.1%).
Results from the analysis showed that anxiety symptom severity was significantly lower in the Q3 tertile of prebiotic food consumption, compared to Q1 and Q2 tertiles.
When adjusted for age and sex, the association between prebiotic food consumption and anxiety remained significant statistically (p < 0.05).
Additionally, the Q3 tertile of prebiotic and probiotic food consumption also had significantly lower anxiety symptom severity, suggesting that the odds ratio of anxiety decreases as the intake of prebiotic and probiotic foods increases.
Differences between men and women
A subgroup analysis found differences in the link between prebiotic and probiotic food consumption and anxiety symptoms among men and women.
While the consumption of prebiotic food was significantly associated with lower odds of anxiety among both men and women, probiotic food had a significant beneficial effect on lowering anxiety symptoms in men but not in women.
“Sex-related differences are well-established in anxiety disorders. Although these differences may be attributed to psychological and cultural factors, biological factors have also been identified to play an important role.
“These include genetic predisposition, brain circuitry, and fluctuating levels of gonadal steroids (sex hormones) in women across the menstrual cycle,” the researchers wrote.
In particular, sex hormones play a pivotal role in the gut microbiota composition, which may increase pro-inflammatory mediators and adverse psychological responses.
For example, women are reported to have lower Bacteroides abundance in their gut microbiome compared to men. Notably, significant reduction in Bacteroides has been shown in the faecal microbiota of individuals with psychological distress.
Furthermore, previous studies have indicated that male and female gut microbiota respond differently to dietary manipulation, and that the male microbiota may be more affected by dietary intake than females.
“Sex disparities in the association between dietary intake and anxiety status could be attributed to the differences in microbial composition.
“However, further multidisciplinary research is needed to obtain a deeper understanding of how the mechanism of gut microbiota may relate to gender differences, and to support the observed relationship between prebiotics, probiotics, and anxiety.”
Microbiota-gut-brain axis
The rising number of anxiety disorder diagnoses globally is partly due to greater disease awareness, as well as modern past-paced life and shifts in dietary patterns.
There is growing evidence that anxiety symptoms could be regulated by nutritional interventions through gut microbiome alterations and reducing inflammation.
Touted as “psychobiotics”, prebiotics and probiotics have been highlighted in several studies not only for their cognitive and systemic effects, but also their promise as anxiolytic agents.
For instance, probiotics have demonstrated their ability to modulate proteins and neurotransmitters, including gamma-aminobutyric acid (GABA), glutamate, histamine, serotonin, and brain-derived neurotrophic factor (BDNF), via the gut-brain axis.
These neurotransmitters are essential for managing neural excitatory-inhibitory balance, mood, and anxiety.
Another potential mechanism of action of probiotics is their anti-inflammatory properties. They have been found to reduce inflammatory cytokines, such as plasma IL-10, and oxidative stress markers.
Notably, Koreans consume a relatively large amount of fermented vegetables, with kimchi accounting for 40 to 45% of the daily total vegetable consumption of the population.
Kimchi is known as a source of diverse lactic acid bacteria. Among them, Lactobacillus plantarum, which has been widely examined for its antibacterial and immune-regulatory characteristics, is said to be responsible for the late stage of kimchi fermentation.
In the present study, fermented probiotic foods, including kimchi, showed a significant positive effect in lowering anxiety symptoms.
“Probiotic organisms are crucial for maintaining intestinal microbiota balance, and prebiotics may be utilised to support the beneficial effects. Thus, proper selection of probiotic strains and prebiotics supplementation may contribute to improving overall effect of probiotics in the gastrointestinal tract, which may in turn confer a beneficial impact on mental health.”
Source: Frontiers in Nutrition
https://doi.org/10.3389/fnut.2024.1385518
“The effect of prebiotic and probiotic food consumption on anxiety severity: a nationwide study in Korea”
Authors: Hyejin Tae and Tae-Suk Kim
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