STRESS
December 20, 2018

Nature's Healing Power, Written in Your Blood

When you're stressed, it shows in your blood. Those markers improve when you spend time in greenery.

Medicine doesn't have to come in a pill. Where you live — specifically, how much green space there is in your neighborhood — can have a profound effect on your heart's health.

Despite the large number of studies showing health benefits from greenery and green spaces, some researchers point out that many findings rely on self-reported information and few, if any, supply details on how green spaces might be responsible for better health.

The findings held true regardless of people's age, sex or ethnicity. They even held true for smokers.

A new study should help satisfy them. It used satellite imagery to quantify how green a location is and measurements of the biomolecules and cell types found in people's blood and urine as indicators of their heart health.

The results provide more evidence that green neighborhoods are good for the heart. They protect people from heart disease, apparently by reducing stress. The greener a neighborhood was, the researchers saw improvements in three significant markers of stress:

  • Urinary epinephrine (adrenaline) fell, indicating less general stress.
  • Another compound, urinary F2-isoprostane, also fell. This is an indicator of oxidative stress, which occurs when the body is unable to neutralize enough of the reactive compounds called free radicals which cause various types of cell damage when they are allowed to circulate in their reactive form.
  • Circulating angiogenic cells in the blood rose. These are cells derived from bone marrow that promote the growth of new blood vessels.
  • These findings held true regardless of people's age, sex or ethnicity. They even held true for smokers.

    Controlled studies of the effects of greenness on people's health are hard to do. That's why most studies on green spaces and health simply compare outcomes in green and less green places. They can suggest that the two are related, but they can't show greenery causes better health, though a famous study did find that people recovered faster in the hospital when they had a view with some greenery in it.

    “Our study shows that living in a neighborhood dense with trees, bushes and other green vegetation may be good for the health of your heart and blood vessels,” said the study's lead author, Aruni Bhatnagar, a professor of medicine at the University of Louisville. “Indeed, increasing the amount of vegetation in a neighborhood may be an unrecognized environmental influence on cardiovascular health and a potentially significant public health intervention.”

    For people who live in cities where green spaces are often few and far between, increasing the amount of vegetation may be difficult. For them, green spaces often mean parks, an amenity whose funding is always in jeopardy, despite their documented benefits. Hopefully, public officials will begin to see parks as a public health necessity rather than a luxury and fund them accordingly.

    The study appears in the Journal of the American Heart Association and is open access.

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