The Lovebug Effect: Is the human biophilic drive influenced by interactions between the host, the environment, and the microbiome?

A 15-day pilot biodiversity intervention with horses in a farm system leads to gut microbiome rewilding in 10 urban Italian children

To provide some glimpses on the possibility of shaping the human gut microbiome (GM) through probiotic exchange with natural ecosystems, here we explored the impact of 15 days of daily interaction with horses on the GM of 10 urban-living Italian children. Specifically, the children were in close contact with the horses in an "educational farm", where they spent almost 10 h/day interacting with the animals. The children's GM was assessed before and after the horse interaction using metabarcoding sequencing and shotgun metagenomics, along with the horses' skin, oral and fecal microbiomes. Targeted metabolomic analysis for GM-produced beneficial metabolites (i.e., short-chain fatty acids) in the children's feces was also performed. Interaction with horses facilitated the acquisition of health-related traits in the children's GM, such as increased diversity, enhanced butyrate production and an increase in several health-promoting species considered to be next-generation probiotics. Among these, the butyrate producers Facecalibacterium prausnitzii and F. duncaniae and a species belonging to the order Christensenellales. Interaction with horses was also associated with increased proportions of Eggerthella lenta, Gordonibacter pamelae and G. urolithinfaciens, GM components known to play a role in the bioconversion of dietary plant polyphenols into beneficial metabolites. Notably, no increase in potentially harmful traits, including toxin genes, was observed. Overall, our pilot study provides some insights on the existence of possible health-promoting exchanges between children and horses microbiomes. It lays the groundwork for an implemented and more systematic enrollment effort to explore the full complexity of human GM rewilding through exchange with natural ecosystems, aligning with the One Health approach.

Diversity and compositional differences of the airborne microbiome in a biophilic indoor environment

Biophilic design based on indoor planting plays an important role in human physical and mental well-being. To investigate and assess the effects of indoor planting on air quality, we sequenced 16S rRNA gene amplicons to compare the airborne bacterial microbiomes of three planting rooms before and after installing natural materials (plants, soil, water, etc.) with distinct biophilic attributes. Incorporation of indoor plantings significantly increased the taxonomic diversity of the airborne microbiome in each room, and we observed different microbiome compositions in each room. The proportional contribution of each bacterial source to the airborne microbiome in the indoor planting rooms was estimated by SourceTracker2. This analysis revealed that the proportion of airborne microbial sources (e.g., plants and soil) varied depending on the natural materials installed. Our results have important implications for indoor planting with biophilic design to control the indoor airborne microbiome.

Combined effects of heatwaves and air pollution, green space and blue space on the incidence of hypertension: A national cohort study

Extreme heat exposure has been associated with hypertension. However, its interactive influences with air pollution, green and blue spaces are unclear. This study aimed to explore the interaction between heatwaves, air pollution, green and blue spaces on hypertension. Cohort data enrolled 6448 Chinese older adults aged 65 years and over were derived from the Chinese Longitudinal Healthy Longevity Survey (CLHLS) between 2008 and 2018. Nine heatwave definitions, combining three heat thresholds (92.5th, 95th, and 97.5th percentiles of daily maximum temperature) and three durations (≥2, 3 and 4 days) were used as time-varying variables in the analysis and were the one-year exposure before survival events. Fine particulate matter (PM ≤2.5 μm in aerodynamic diameter (PM_2.5)), the Normalized Difference Vegetation Index (NDVI) and the average proportion of open water bodies were used to reflect the air pollution, green and blue space exposures, respectively. PM_2.5, green and blue space exposures were time-varying indicators and contemporaneous with heatwaves. Mixed Cox models with time-varying variables were fitted to assess the multiplicative and additive interaction of heatwaves, PM_2.5, and green and blue spaces on hypertension, measured by a traditional product term with the ratio of hazard ratio (HR) and relative risk due to interaction (RERI), respectively. A positive multiplicative (HRs >1) and additive interaction (RERIs >0) between heatwaves and higher PM_2.5 levels was observed. There was a synergistic effect between heatwaves and decreasing greenness levels on hypertension incidence on additive and multiplicative scales. No significant interaction between heatwaves and blue space was observed in the analysis. The combined effects of heatwaves, air pollution, green and blue space exposures on the risk of hypertension varied with age, gender, and educational attainment. This study's findings complemented the existing evidence and revealed synergistic harmful impacts for heatwaves with air pollution and lack of green space on hypertension incidence.

Psychobiotic Effects on Anxiety Are Modulated by Lifestyle Behaviors: A Randomized Placebo-Controlled Trial on Healthy Adults

Psychobiotics are modulators of the Microbiota-Gut-Brain Axis (MGBA) with promising benefits to mental health. Lifestyle behaviors are established modulators of both mental health and the MGBA. This randomized placebo-controlled clinical trial (NCT04823533) on healthy adults (N = 135) tested 4 weeks of probiotic supplementation (Lactobacillus helveticus R0052 and Bifidobacterium longum R0175). We assessed effects on wellbeing, quality of life, emotional regulation, anxiety, mindfulness and interoceptive awareness. We then analyzed if lifestyle behaviors modulated probiotic effectiveness. Results showed no significant effects of probiotic intake in whole sample outcomes. Correlational analyses revealed Healthy Behaviors were significantly correlated with wellbeing across scales. Moreover, the linear mixed-effects model showed that the interaction between high scores in Healthy Behaviors and probiotic intake was the single significant predictor of positive effects on anxiety, emotional regulation, and mindfulness in post-treatment outcomes. These findings highlight the relevance of controlling for lifestyle behaviors in psychobiotic and mental health research.

Beyond "bluespace" and "greenspace": A narrative review of possible health benefits from exposure to other natural landscapes

Numerous studies have highlighted the physical and mental health benefits of contact with nature, typically in landscapes characterized by plants (i.e., "greenspace") and water (i.e., "bluespace"). However, natural landscapes are not always green or blue, and the effects of other landscapes are worth attention. This narrative review attempts to overcome this limitation of past research. Rather than focusing on colors, we propose that natural landscapes are composed of at least one of three components: (1) plants (e.g., trees, flowering plants, grasses, sedges, mosses, ferns, and algae), (2) water (e.g., rivers, canals, lakes, and oceans), and/or (3) rocks and minerals, including soil. Landscapes not dominated by plants or liquid-state water include those with abundant solid-state water (e.g., polar spaces) and rocks or minerals (e.g., deserts and caves). Possible health benefits of solid-state water or rock/mineral dominated landscapes include both shorter-term (e.g., viewing images) and longer-term (e.g., living in these landscapes) exposure durations. Reported benefits span improved emotional and mental states and medical treatment resources for respiratory conditions and allergies. Mechanisms underlying the health benefits of exposure consist of commonly discussed theories in the "greenspace" and "bluespace" literature (i.e., instoration and restoration) as well as less discussed pathways in that literature (i.e., post-traumatic growth, self-determination, supportive environment theory, and place attachment). This is the first review to draw attention to the potential salutogenic value of natural landscapes beyond "greenspace" and "bluespace." It is also among the first to highlight the limitations and confusion that result from classifying natural landscapes using color. Since the extant literature on natural landscapes - beyond those with abundant plants or liquid-state water - is limited in regard to quantity and quality, additional research is needed to understand their restorative potential and therapeutic possibilities.

Perspectives on Inequity and Health Disparities in Chile and Their Relationship to Microbial Ecology

Among countries in the Organisation for Economic Cooperation and Development (OECD), Chile stands out as having important inequalities in income distribution, dietary quality, access to urban green spaces, and health outcomes. People in lower socioeconomic groups consistently show higher rates of noncommunicable chronic diseases and are being hit the hardest by the COVID-19 pandemic. These chronic conditions are increasingly considered to be shaped, or affected by, the human gut microbiome. Moreover, inequity as an overarching concept might also be associated with microbial patterns and if so, this may represent a novel pathway through which to address health and other disparities. Focusing on the case of Chile, our goal is to contribute to a critical discussion and motivate researchers and policymakers to consider the role of the microbiome in social equity in future endeavors.

An Analysis of Theoretical Perspectives in Research on Nature-Based Interventions and Pain

Chronic pain results from a complex series of biomechanical, inflammatory, neurological, psychological, social, and environmental mechanisms. Pain and pain-related diseases are the leading causes of disability and disease burden globally. Employing nature-based interventions for the treatment of pain is an emerging field. Current theory driving the suggested mechanism(s) linking the pain reducing effects of nature-based interventions is lacking. A two-step approach was taken to complete a theoretical review and analysis. First, a literature review was completed to gather a substantive amount of research related to theoretical frameworks on the topic of nature-based interventions and pain. Secondly, a theoretical analysis as proposed by Walker and Avant was completed to explore current theoretical frameworks accepted in the literature on nature-based interventions and pain. Stress reduction theory and attention restoration theory were the most common theoretical frameworks identified. Neither theoretical framework explicitly identifies, describes, or intends to adequately measure the concept of pain, revealing a limitation for their application in research with nature-based interventions and pain. Theoretical development is needed, as it pertains to nature-based interventions and pain. Without this development, research on nature-based interventions and pain will continue to use proxy concepts for measurement and may result in misrepresented findings.

Does Bird Diversity Affect Public Mental Health in Urban Mountain Parks?-A Case Study in Fuzhou City, China

Intensified urbanization has caused a linear decline in the quality of urban biodiversity and indirectly harms our current human settlement environment. Urban mountain parks provide a refuge for the animals and plants and play a vital role in satisfying residents’ lives. At present, few studies are focusing on the impact of biodiversity on human mental health benefits of urban mountain parks in high-density construction areas along the coast of the Eastern Hemisphere. Here, we examined the relationship between bird abundance, Shannon diversity, Simpson diversity, and Richness and momentary mental health (positive, negative, and anxiety) in urban mountain parks. The timed species counts method was used to conduct three surveys of birds in urban mountain parks, and linear regression was performed on the relationship between bird diversity and mental health among sites. According to the regression model results, we found no significant correlation in any disturbance levels. As urban mountain parks are an essential part of the human settlement environment, how to improve the biodiversity and mental health of urban mountain parks is one of the focuses of research on biodiversity well-being in the future. Urban planning authorities and public mental health researchers should pay attention to the importance of biodiversity in urban development and consider how to realize the beautiful vision of the harmonious coexistence of humans, animals, plants, and the environment in which we live.

Associations of greenness surrounding schools with blood pressure and hypertension: A nationwide cross-sectional study of 61,229 children and adolescents in China

BACKGROUND

Greenness exposure may lower blood pressure. However, few studies of this relationship have been conducted with children and adolescents, especially in low and middle-income countries.

OBJECTIVES

To evaluate associations between greenness around schools and blood pressure among children and adolescents across China.

METHODS

We recruited 61,229 Chinese citizens aged 6-18 years from 94 schools in a nationwide cross-sectional study in seven Chinese provinces/province-level municipalities. Participants' blood pressures and hypertension were assessed with standardized protocols. Greenness levels within 500 m and 1,000 m of each school were estimated with three satellite-based indices: vegetation continuous fields (VCF), normalized difference vegetation index (NDVI), and soil adjusted vegetation index (SAVI). Generalized linear mixed models were used to evaluate associations between greenness and blood pressure, greenness and prevalent hypertension, using coefficient and odds ratio respectively. Stratified analyses and mediation analyses were also performed.

RESULTS

One interquartile range increase in greenness was associated with a 17%-20% reduced prevalence of hypertension for all measures of greenness (odds ratios for VCF_500m = 20% (95% CI:18%, 23%); for NDVI_500m = 17% (95% CI:13%, 21%); and for SAVI_500m = 17% (95% CI: 13%, 20%). Increases in greenness were also associated with reductions in systolic blood pressure (0.48-0.58 mmHg) and diastolic blood pressure (0.26-0.52 mmHg). Older participants, boys, and urban dwellers showed stronger associations than their counterparts. No evidence of mediation was observed for air pollution (i.e., NO₂ and PM_2.5) and body mass index.

CONCLUSION

Higher greenness around schools may lower blood pressure levels and prevalent hypertension among Chinese children and adolescents, particularly in older subjects, boys, and those living in urban districts. Further studies, preferably longitudinal, are needed to examine causality.

Greenspace and human health: An umbrella review

Multiple systematic reviews on greenspace and health outcomes exist, but the overall evidence base remains unclear. Therefore, we performed an umbrella review to collect and appraise all relevant systematic reviews of epidemiological studies on greenness exposure and health. We searched PubMed, Embase, and Web of Science from inception to June 28, 2021, and screened references of relevant articles. Systematic reviews with or without meta-analyses of epidemiological studies that examined the associations of greenness with any health outcome were included. Two independent investigators performed study selection and data extraction. We also evaluated the methodological quality of the included systematic reviews using the “Assessing the Methodological Quality of Systematic Reviews 2” checklist. A total of 40 systematic reviews and meta-analyses were included, of which most were cross-sectional studies conducted in high-income countries. Greenspace exposure was estimated with various objective and subjective parameters. Beneficial associations of greenspace with all-cause and stroke-specific mortality, CVD morbidity, cardiometabolic factors, mental health, low birth weight, physical activity, sleep quality, and urban crime were observed. No consistent associations between greenspace and other health outcomes (e.g., cancers) were observed. Most of the included systematic reviews and meta-analyses had one or more limitations in methodology. Our findings provide supportive evidence regarding the beneficial effects of greenspace exposure on some aspects of human health. However, the credibility of such evidence was compromised by methodological limitations. Better performed systematic reviews and meta-analyses as well as longitudinal designed primary studies are needed to validate this conclusion.

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The evidence concerning greenspace and health outcomes remains unclear

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We performed an umbrella review of 40 systematic reviews on greenspace and health

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Greenspace exposure was estimated with various objective and subjective parameters

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Greenspace was beneficially associated with several aspects of human health

Biophilia as Evolutionary Adaptation: An Onto- and Phylogenetic Framework for Biophilic Design

Biophilia is a human personality trait described initially by Erich Fromm and later by E.O. Wilson, both of whom agree that biophilia has a biological basis and that it is fundamental to develop harmonious relationships between humans and the biosphere. This review aims at establishing a definition of biophilia as an evolutionary process. To this end, the most significant studies of evolutionary psychology were considered, to outline the fundamental characteristics of a hypothetical biophilic temperament/personality and to reconstruct a plausible history of biophilia as an evolutionary process. This process considers different typologies of Nature (wilderness, rural, and urban) and human cultures (Paleolithic, Neolithic, and Burg) and leads us to consider environmental preference and psycho-physiological recovery in relation to the threshold of time spent in contact with Nature. Unfortunately, modern people, especially children, lack direct and frequent contact with Nature and this can have negative consequences on their physical and mental health. Biophilic design, considering the evolutionary roots of this architectural approach, is an effective way of planning/designing interior and urban environments to stimulate the innate biophilia of the individual.

The potential of outdoor environments to supply beneficial butyrate-producing bacteria to humans

Butyrate is an important mediator of human health and disease. The mechanisms of action of butyrate are becoming increasingly well-known. Many commensal bacteria that inhabit the human gut can synthesise butyrate, which is then absorbed into the human host. Simultaneously, several immune- and inflammatory-mediated diseases are being linked to insufficient exposure to beneficial microbes from our environment, including butyrate-producing bacteria. However, the role of outdoor environmental exposure to butyrate-producing bacteria remains poorly understood. Here we review the literature on the human exposure pathways to butyrate-producing bacteria, with a particular focus on outdoor environmental sources (e.g. associated with plants, plant-based residues, and soil), and the health implications of exposure to them. Emerging evidence suggests that environmental butyrate-producers may help supplement the human gut microbiota and represent an important component of the Biodiversity and Old Friends hypotheses. Improving our understanding of potential sources, precursors, and exposure pathways of environmental butyrate-producers that influence the gut microbiota and butyrate production offers promise to advance multiple disciplines of health and environmental science. We outline research priorities to address knowledge gaps in the outdoor environment-butyrate-health nexus and build knowledge of the potential pathways to help optimise exposure to human-beneficial butyrate-producing bacteria from the outdoor environment during childhood and adulthood.

Germaphobia! Does Our Relationship With and Knowledge of Biodiversity Affect Our Attitudes Toward Microbes?

Germaphobia – a pathological aversion to microorganisms – could be contributing to an explosion in human immune-related disorders via mass sterilization of surfaces and reduced exposure to biodiversity. Loss of biodiversity and people’s weaker connection to nature, along with poor microbial literacy may be augmenting the negative consequences of germaphobia on ecosystem health. In this study, we created an online questionnaire to acquire data on attitudes toward, and knowledge of microbes. We collected data on nature connectedness and interactions with nature and explored the relationships between these variables. Although the study had an international reach (n = 1,184), the majority of responses came from England, United Kingdom (n = 993). We found a significant association between attitudes toward microbes and both duration and frequency of visits to natural environments. A higher frequency of visits to nature per week, and a longer duration spent in nature per visit, was significantly associated with positive attitudes toward microbes. We found no association between nature connectedness and attitudes toward microbes. We found a significant relationship between knowledge of “lesser known” microbial groups (e.g., identifying that fungi, algae, protozoa, and archaea are microbes) and positive attitudes toward microbes. However, we also found that people who identified viruses as being microbes expressed less positive views of microbes overall–this could potentially be attributed to a “COVID-19 effect.” Our results suggest that basic microbial literacy and nature engagement may be important in reducing/preventing germaphobia-associated attitudes. The results also suggest that a virus-centric phenomenon (e.g., COVID-19) could increase broader germaphobia-associated attitudes. As the rise of immune-related disorders and mental health conditions have been linked to germaphobia, reduced biodiversity, and non-targeted sterilization, our findings point to a feasible strategy to potentially help ameliorate these negative consequences. Further research is needed, but greater emphasis on microbial literacy and promoting time spent in nature could potentially be useful in promoting resilience in human health and more positive/constructive attitudes toward the foundations of our ecosystems—the microorganisms.

Increased plant species richness associates with greater soil bacterial diversity in urban green spaces

The vegetation and soil microbiome within urban green spaces is increasingly managed to help conserve biodiversity and improve human health concurrently. However, the effects of green space management on urban soil ecosystems is poorly understood, despite their importance. Across 40 urban green spaces in metropolitan Adelaide, South Australia, we show that soil bacterial communities are strongly affected by urban green space type (incl. sport fields, community gardens, parklands and revegetated areas), and that plant species richness is positively associated with soil bacterial diversity. Importantly, these microbiome trends were not affected by geographic proximity of sample sites. Our results provide early evidence that urban green space management can have predictable effects on the soil microbiome, at least from a diversity perspective, which could prove important to inform policy development if urban green spaces are to be managed to optimise population health benefits.

The Holobiont Blindspot: Relating Host-Microbiome Interactions to Cognitive Biases and the Concept of the "Umwelt"

Cognitive biases can lead to misinterpretations of human and non-human biology and behavior. The concept of the Umwelt describes phylogenetic contrasts in the sensory realms of different species and has important implications for evolutionary studies of cognition (including biases) and social behavior. It has recently been suggested that the microbiome (the diverse network of microorganisms in a given environment, including those within a host organism such as humans) has an influential role in host behavior and health. In this paper, we discuss the host’s microbiome in relation to cognitive biases and the concept of the Umwelt. Failing to consider the role of host–microbiome (collectively termed a “holobiont”) interactions in a given behavior, may underpin a potentially important cognitive bias – which we refer to as the Holobiont Blindspot. We also suggest that microbially mediated behavioral responses could augment our understanding of the Umwelt. For example, the potential role of the microbiome in perception and action could be an important component of the system that gives rise to the Umwelt. We also discuss whether microbial symbionts could be considered in System 1 thinking – that is, decisions driven by perception, intuition and associative memory. Recognizing Holobiont Blindspots and considering the microbiome as a key factor in the Umwelt and System 1 thinking has the potential to advance studies of cognition. Furthermore, investigating Holobiont Blindspots could have important implications for our understanding of social behaviors and mental health. Indeed, the way we think about how we think may need to be revisited.