Grandma was right: Why it's good for your health to be outdoors

Sure, there are treadmills at climate-controlled gyms and Nintendo's Wii is still going strong with indoor workouts like Zumba Fitness 2.

And yet, old-fashioned advice to "go outside and play" is still the best for your health, according to researchers the world over. In one study published by the NCBI, researchers found a decrease in both heart rate and cortisol levels when participants spent time in the forest instead of the city.

"Stressful states can be relieved by forest therapy," the researchers concluded.

The encouragement to "get outdoors" for health holds even in the face of the Asthma and Allergy Foundation of America's assertion that pollen seasons have gotten stronger and longer over the years. The workaround: the AAFA recommended limiting outdoor activities, but only on days when pollen is high for the trees or grasses you are allergic to.

Being outside delivers other health rewards, too, from sharp mental health benefits to improved memory and decreased inflammation.

Here are four of the most significant health benefits from spending time outdoors, according to Business Insider:

Walking in the woods can improve your short-term memory. "Nature walks have memory-promoting effects that other walks don't," BI noted, citing a study where participants who walked among trees did 20 percent better on a memory test than those who had taken in city sights.

Outdoor experiences can fight depression and anxiety. Time in nature may combat depression, anxiety and other mental health issues, especially when combined with exercise.

One study associated walks in the forest with decreased levels of anxiety and bad moods while another found outdoor walks could be "useful clinically as a supplement to existing treatments" for major depressive disorder, BI reported.

Being outdoors has a demonstrated de-stressing effect. One study published by NCBI found that students sent into the forest for two nights had lower levels of the stress marker cortisol than those who spent that time in a city.

Spending time outside reduces inflammation. Inflammation in overdrive is associated with ills that include autoimmune disorders, inflammatory bowel disease, depression and cancer. "Spending time in nature may be one way to help keep that in check," BI noted, referencing a study where students who spent time in the forest had lower levels of inflammation than those who spent time in the city.