Nineteenth-century American essayist Ralph Waldo Emerson once said: “Nature always wears the colors of the spirit.” British actress Audrey Hepburn, who was a passionate, lifelong gardener, said: “To plant a garden is to believe in tomorrow.”
Both were on target.
Pregnant women who live in greener neighborhoods may have lower levels of long-term stress, according to a new study led by researchers from Bar-Ilan University’s Azrieli Faculty of Medicine in Safed.
Colleagues at Tel Aviv University, the Hebrew University of Jerusalem, the Helen Schneider Hospital for Women at the Rabin Medical Center-Beilinson Campus in Petah Tikva, and the Alfred Wegener Institute in Bremerhaven, Germany, collaborated on the research.
Grass, trees, plants linked to brain’s production of less cortisol, cortisone
They found that greater exposure to residential greenery during pregnancy was associated with lower levels of cortisol and cortisone – two key stress hormones that can affect both maternal and fetal health.
Their research has been published in the journal Environmental Epidemiology under the title “Satellite and ground-level residential greenness and hair steroid hormones during pregnancy.”
Unlike stress hormones measured in blood, saliva, or urine, which reflect stress over minutes or hours, hormones measured in hair provide a profile of stress hormones accumulated over several months.
By analyzing hair samples from hundreds of pregnant women, the researchers were able to assess chronic stress levels during the second trimester of pregnancy. Higher levels during pregnancy are linked with an increased risk of complications that negatively impact the health of the mother or the fetus.
The team found that women living in greener environments during their second trimester had significantly lower concentrations of cortisol and cortisone in their hair.
Their findings were consistent across several measures of residential greenery and across different distances near participants’ homes. “Our findings suggest that exposure to greenery around the home is associated with reduced chronic stress hormones during pregnancy,” said Sohini Bhattacharya, a doctoral candidate in her fourth year at medical school who comes from a green suburb of Calcutta, India.
“This is important because prolonged exposure to elevated stress hormones can negatively affect both the mother and the developing fetus.”
The current study builds on earlier research by the same team, which found an association between residential greenness and lower hair cortisol levels during the first trimester of pregnancy.
The new study expands those findings by examining additional hormones, later stages of pregnancy, and more detailed measures of greenery.
Researchers collected hair samples and analyzed hormone levels using advanced laboratory techniques from 385 pregnant women recruited from the Helen Schneider Hospital, who had no pregnancy complications in the past and lived in the Petah Tikva area.
Assuming an average hair growth of one centimeter per month, the hair representing the second trimester (14 to 27 weeks’ gestational age) was cut, weighed, cleaned, placed on aluminum foil, and kept in paper envelopes for analysis.
To estimate exposure to greenery, the team measured vegetation around participants’ homes using satellite imagery and the widely used Normalized Difference Vegetation Index.
They then applied a novel method based on Google Street View images. Both methods pointed to the same conclusion: women living in greener surroundings had lower long-term stress hormone levels.
Asked why the team’s study was based on both satellite images and Google Street View, Bhattacharya explained that “other studies were only satellite-based, so the researchers had only a bird’s-eye view from above. But we used the street view so we could see images in real time and identify various types of greenery.”
One of the study’s most unexpected findings emerged from the street-level analysis. Women living in areas with a higher percentage of grass around their homes had notably lower cortisol and cortisone levels than women living in less grassy environments.
The two stress hormones play important roles in regulating metabolism, immune function, sleep cycles, and maintaining pregnancy – but prolonged elevation of these hormones can be harmful.
Previous studies suggested that exposure to natural environments may reduce stress but mostly relied on self-reported measures or short-term biological indicators. Few studies have examined long-term stress using hair samples, and even fewer have focused specifically on pregnant women.
‘The more grass, the lower the women’s stress hormones’
“I saw there were a lot of influences on health in pregnant women, and I find greenness very interesting,” Bhattacharya told The Jerusalem Post in an interview.
Asked what surprised her among the results, she noted that the positive effect of seeing and walking near grass was not expected.
“The more grass, the lower the women’s stress hormones. It can also improve their sleep quality, so it’s holistic.”
The team measured both cortisol and cortisone rather than cortisol alone, because “during pregnancy, natural cortisol levels naturally increase to support fetal organ maturation and growth.
“The body actively converts much of this active cortisol into inactive cortisone to protect the developing baby from excessive stress hormone exposure. Too much is harmful to a fetus,” Bhattacharya explained.
Cortisol, which is biologically active and circulates in the mother’s blood, is converted into cortisone in a pregnant woman, and this is one of the most crucial mechanisms for protecting a developing baby – acting like a protective shield.
This cortisol is converted into cortisone, which is biologically inactive and prevents the cortisol from reaching the fetus in harmful amounts.
The team analyzed the women’s hair – a strand just three centimeters long – and not saliva, urine, or blood, because these samples reflect their hormonal status for just a few hours before they’re tested, but as hair grows for years, it reflects its chronic hormonal status, she continued.
If a pregnant woman lives in a neighborhood with little greenery, it’s recommended that she walk daily in a park or forest or at least see grass – or she can grow plants on her balcony.
Her physician should recommend this, noted Bhattacharya. But the study did not investigate the “ideal dose” – how many minutes per day or hours per week that pregnant women should be in green spaces.
“If city planners and local authorities seek cost-effective ways to improve public health and well-being, they should plant more green spaces – a task that is relatively inexpensive to carry out – to reduce stress,” she said.
The findings come at a time when many populations, including those in Israel, are experiencing increased stress due to ongoing conflict, climate change, and rapid urbanization.
The study’s lead researcher, Bar-Ilan University medical faculty member Prof. Keren Agay-Shay, concluded that their findings “support efforts to preserve and expand green spaces and greenness in residential neighborhoods.
“As cities continue to grow around the world, integrating trees, grass, and other vegetation into urban environments may provide a simple and accessible strategy for improving public health.”
The results “highlight the importance of integrating natural environments into public health strategies, particularly for vulnerable populations,” Agay-Shay added.
Source:
www.jpost.com
