How 20 minutes of nature can boost your health

If you've ever felt calmer after a walk in the park or a stroll through the woods, it's not your imagination - it's biology.

Being outdoors can trigger measurable changes inside your body from lowering stress hormones, easing blood pressure and even improving your gut health.

You don't have to hike for hours to feel these benefits as maximum impact happens after just 20 minutes, so even a lunchtime walk to the park and a sandwich on a bench a few times a week can benefit your body and mind.

Here are four ways that being among nature can help improve your health.

Smelling nature is just as powerful as seeing and hearing it.

The scent of trees and soil is full of organic compounds released by plants and "when you breathe them in, some molecules pass into the bloodstream."

Willis says pine is a good example of this as the smell of a pine forest can make you calmer within just 90 seconds and that effect lasts for about 10 minutes.

You may think that the relaxing effect of nature is all in your mind, but another study found that even very young babies with no memory associated with particular smells, still calmed down when another scent associated with calming, limonene was puffed into the room they were in.

As well as soothing your mind, nature can also help boost your microbiome as soil and plants are full of good bacteria.

"They're the same kinds of good bacteria we pay for in probiotics or drinks," Willis explains.

Prof Ming Kuo has studied the effect on factors such as infection susceptibility as well as mental health and says breathing in certain ones have the potential to boost your mood; and the antimicrobial chemicals released by plants – called phytoncides – could help fight disease.

Dr Chris van Tulleken says as an infection scientist he sees nature as a positively challenging environment that "tickles your immune system".

He gets his children to play with dirt in the forest which then enters their system through the nose or mouth.

Of course, not everyone can head into the woods on a whim but the good news is, you don't have to.

Even small touches of nature at home can make a difference, according to Willis.

Visually, flowers such as white or yellow roses have been shown to create the greatest calming effect on brain activity.

When it comes to smell, use a diffuser with essential oils like pinene which can help you feel calm.

And if all else fails, even a photo of a forest can help.

Research shows that looking at pictures of nature on your laptop or simply gazing out at something green can trigger the same calming brainwave changes and reduce stress.

"Every bit seems to help," says Prof Ming Kuo.