Analysis does not find association between green space and oxidative stress is related to frequency of children's physical activity

Children who live and study near green spaces suffer less oxidative stress, study finds

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A study led by the Barcelona Institute for Global Health (ISGlobal), a centre supported by the "la Caixa" Foundation, has analysed for the first time the relationship between exposure to different green spaces and oxidative stress in children. The analysis concludes that greater exposure to vegetation is associated with lower levels of oxidative stress and that this association is observed regardless of the physical activity carried out by the children.

Oxygen is essential for a large number of biochemical reactions that keep us alive, but during its oxidation process harmful reactive substances are generated that the body cannot always neutralise quickly or whose damage it is unable to repair. This results in so-called oxidative stress, which causes us to age or even fall ill.

So far, several studies have shown that having green spaces at home has a positive effect on health, especially because they improve mental health and promote physical exercise, which reduces the risk of becoming overweight or obese. But the direct effects of this vegetation on biological processes, for example on inflammation and oxidative stress, have been less well studied. This is particularly important for understanding the role that green spaces can play in respiratory and allergic diseases.

A study with over 300 Italian children

In order to explore whether green spaces could be associated with lower levels of oxidative stress in children, and also whether physical activity played a role in this possible association, 323 healthy children aged 8-11 years enrolled in five primary schools in Asti, a small town in north-western Italy, were analysed.

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Parents completed a questionnaire that included information on how often their children were physically active. Oxidative stress was quantified in urine by measuring the concentration of the compound isoprostane. In addition, green and school spaces were defined using the Normalised Difference Vegetation Index (NDVI), and the vegetation portion was also estimated. Multi-site exposures were obtained by taking into account the NDVI of the home and school, and the time spent by the child at each site.

Possible explanations

Several biological mechanisms could explain this direct relationship between green areas and oxidative stress in children. Firstly, "increased exposure to these areas may contribute to children's immune development by bringing them into contact with organisms that often colonise natural environments", explains Judith Garcia-Aymerich, researcher and head of the Noncommunicable Diseases and Environment programme at ISGlobal, who is the last author of the study. In addition, being in contact with green spaces can increase vitamin D synthesis through ultraviolet radiation from the sun. This vitamin acts as an antioxidant that prevents the negative effects of oxidative stress and inflammation. Finally, vegetation improves air quality in urban areas.

Physical activity has no influence

Although proximity to green space has been associated with increased physical activity, which in turn affects oxidative stress, the study found no evidence that exercise was involved in the association between green space and oxidative stress.

Garcia-Aymerich says that "we do not know the short- and long-term effects that excess oxidative stress has on health, so we need to continue researching and supporting public health and urban strategies that favour green spaces".

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