Human milk has evolved to promote survival and healthy development of the infant both through its nutritional composition and with non-nutritive bioactive factors such as hormones, growth factors, antibodies and human milk oligosaccharides (HMOs).
HMOs are strong candidates for having specific links with the residential green environment, due to the suggested role of environmental microbiota in their composition. HMOs are a group of more than 150 different complex carbohydrates that together constitute the third largest component in human milk. The total amount and composition varies largely between women, and is driven by genetics, nutrition and exercise, as well as environmental measures such as geographical areas and seasons.
HMOs have several important health-related functions for the infant including shaping the gut microbiota by promoting the growth of specific microbes, preventing pathogen invasion and attachment, and altering immune cell responses.
Researchers at the University of Turku and Turku University Hospital, in Finland, therefore aimed to investigate the associations between properties of the mother’s residential green environment (greenness, Vegetation Cover Diversity (VCDI) and Naturalness Index (NI)), and the composition of human milk oligosaccharides (HMOs) in their breastmilk (data from the STEPS Study, N = 795 mothers).
Low NI values represented mainly asphalt covered residential and industrial areas, while high NI values included non-built areas, e.g., natural bare surfaces, water bodies, wetlands and different types of forests.
The team hypothesised that the greater the diversity and proportion of the green environments, the greater are HMO diversity and HMO concentrations.
In line with their hypothesis, they found that HMO diversity increased and concentrations of several individual HMOs and HMO groups changed with increased VCDI and NI.
Specifically, one standard deviation higher NI was associated with increased HMO diversity, with NI associated with 11 individual HMO components, 2′FL, 3FL, 3′SL, LNFP I, LSTb, LSTc, DFLNT, DSLNT, FLNH, DFLNH, DSLNH.
Non-secretor mothers are capable of producing only small amounts of 2′FL and LNFP-I but their HMO profile differs from secretor mothers also by the amounts of several other HMO components. In this study, some significant differences were detected between secretor and non-secretor mothers and many of the associations with the residential green environment were stronger in non-secretor mothers (the non-secretor phenotype is more prevalent in Africa, Central Asia, Far East and Pacific regions possibly due to the need for protection against certain pathogens).
The topic of HMOs will be discussed during NutraIngredients' Probiota event taking place in Barcelona on February 6-8 2023.
Dr Lars Bode, PhD, Professor & Director, University of California, San Diego, will open the show by discussing opportunities for targeted pre-, pro- and synbiotics, within human milk oligosaccharides (HMOs).
Dr Bode is Professor of Pediatrics, Chair of Collaborative Human Milk Research, the founding Director of the Mother-Milk-Infant Center of Research Excellence (MOMI CORE), as well as the Human Milk Institute (HMI) at the University of California in San Diego. He has been working on human milk oligosaccharides (HMOs) for over 20 years.
The associations observed between NI and HMO composition suggests that not only green spaces but also other natural features, such as water areas and wetlands, may have an important role in HMO composition.
To the authors' knowledge, only one previous study has examined human milk composition in relation to the properties of the residential green environment, showing that human milk fungi were not associated with residential NDVI.
The impact on health
Higher gut microbiota diversity in early life has been associated with reduced risk of health concerns such as asthma and allergic diseases. Furthermore, higher HMO diversity and higher concentrations of HMOs have been connected directly to lower risks of several diseases in infancy.
Moreover, Lagström et al. 2020 found in this same study population that higher HMO diversity but lower concentrations of 2’FL were associated with lower height and weight in early childhood in Finland. These results thus suggest that higher HMO diversity and lower concentrations of 2′FL with higher VCDI and NI may protect from obesity development in children in this western population.
Although the team speculates that the residential green environment may be associated with HMO composition via environmental microbial diversity, there are other routes that could have led to these associations. For example, residential green environment may modify the HMO composition by increasing physical activity and relieving mental stress. They did not have information from mother’s physical activity levels at the time of milk collection but they tested associations between HMOs and residential socioeconomic disadvantage, which has previously been connected to increased risk of mental disorders, and found no clear evidence of a link between the two.
The authors also those they only had one milk sample from each mother so they could not investigate within mother variation in HMO composition in relation to changing residential location, which would have made the study stronger.
"Residential green environments are associated with human milk oligosaccharide diversity and composition"
Lahdenperä, M., Galante, L., Gonzales-Inca, C. et al.