5 Things Science Says Happen to Your Body When You Spend Time in Nature

Spending time in nature is linked to measurable changes in the body, and researchers have tracked them using saliva samples, blood pressure readings and sleep measurements. Many of the effects appear after modest amounts of time outdoors, although a few come from studies of longer trips, and the research on each is still growing.

1. Stress Hormone Levels Drop

Time among trees is associated with lower levels of cortisol and adrenaline , the body's main stress hormones. A University of Michigan study of city residents found the steepest cortisol drop came after roughly 20 to 30 minutes of sitting or walking somewhere that felt like nature, and the benefit kept growing at a slower rate after that. That drop came on top of cortisol's normal daily decline. Participants didn't need a trail or a forest, since yards and neighborhood parks counted, and walking or sitting worked equally well.

2. Mood Improves

Time outdoors is tied to better mental health , and in a 2022 study, walking in an urban park improved mood compared with walking in a built-up setting. Even a 15-minute walk through woods helped relieve stress in one 2019 study, so a short walk during a lunch break or around the neighborhood is enough to try.

3. Heart Rate and Blood Pressure Come Down

Qing Li's studies in Japan found lower pulse rates and blood pressure after forest visits than on city days, and a 2022 study found that a walk in a forest park affected cardiovascular function more than a walk in a city park did. Forest bathing researchers recommend slow walking and sitting among trees rather than strenuous exercise, since heavy exertion raises stress hormones and can cancel out the benefit.

4. Immune Cell Activity Rises

Li's research also measured natural killer cells, a type of white blood cell involved in responding to infected and abnormal cells. After long forest walks, participants showed higher activity from these cells, and in one study the increase lasted at least seven days. Li links part of the effect to phytoncides, chemicals released by trees. The number of studies is still limited, so these results are best treated as promising rather than settled.

5. Your Body Clock Adjusts

In one Colorado study, a weekend camping trip moved participants' internal clocks earlier, while people who stayed home drifted later over the same weekend. Natural light seems to drive the effect, because campers were exposed to far more of it than they normally get, and melatonin, the hormone that rises at night, began climbing sooner as a result. Spending more daytime hours outside, and dimming screens and bright lights at night, may support the same pattern at home.

None of these effects depend on a wilderness trip, since short daily visits to a park or yard add up and a longer outing on a weekend can add more. Try spending 20 minutes outside this week, without a phone if you can, and notice how you feel afterward, then lengthen the visit if it helps.

by a T.Smaltsar, Editor.