Three of every five people worldwide will live in a city by 2030, according to a new report that aims to improve health by restoring nature into the urban jungle.

University College London and the Lancet Commission on Healthy Cities explored case studies in crowded metropolises such as London, Bogota, Accra and Toronto to see how planning projects affected the health of city dwellers, especially among the poor.

Toronto's 1,500 urban parks and 12 per cent of surface devoted to green space was cited as an example of how urban planning can deliver green infrastructure to support physical activity, social encounters and engagement with nature.

Type 2 diabetes rates in the city were reduced in areas with parks and other green spaces, but assessments showed less green infrastructure was provided in low-income areas and for the elderly, the report noted.

Michelle Andrews grew up in the natural wooded beauty of northern Ontario and now bikes through Toronto's High Park to go to and from work downtown.

"Instant calm," Andrews said of the slower pace of cycling through the park compared with the busy street portion of her commute. "I relax right away."

In a study published in the May issue of the Journal of Affective Disorders, Mark Berman, a post-doctoral researcher with the Rotman Research Institute at Baycrest in Toronto, found that 20 people with an average age of 26 who were diagnosed with clinical depression scored better on a series of tests of attention and short-term memory when they walked in a quiet nature setting compared with a noisy urban setting.

"There is so much distraction, so much stimulation that people have to process," in the hectic city, Berman said.

Beyond mood benefits

The brain's attention resources seem to get diverted, preventing it from relaxing and allowing the mind to wander the way it does when enjoying the chirps of birds and sun kissed leaves.

No one knows what features of nature lead to the benefits but a better mood alone doesn't explain it. Participants' moods also improved when walking through the city, Berman found.

Health impacts are a growing focus in urban planning, said David Harrison, chair of the Canadian Institute of Planners' Healthy Communities committee.

"People are starting to get it and I think that we'll see increased collaboration between the health and planning professions around our decision making," Harrison said from Dartmouth. "We need to look at all ways to resolve the incidence of chronic disease in Canada."

The London-based researchers said cities should focus on experimenting with health projects at the neighbourhood level, whether in slums in Mumbai or urban agriculture in developed countries.

Their other recommendations were:

  • City governments should build political alliances for urban health.
  • Governments need to identify the health inequalities in cities.
  • Urban planners should include health concerns in their plans, regulations, and decisions.

The report appears in Wednesday's issue of the Lancet.

With files from CBC's Kelly Crowe and Pauline Dakin