Eating from the streets would be a recipe for disaster in most cosmopolitan capitals. Dirt, dust, pollution and filth are a breeding ground for disease. But professional forager Anna Nyman insists the natural bacteria thriving on herbs and wildflowers in Helsinki’s parklands are good for your gut.

“Everything in the supermarket has been sprayed,” says the gently spoken, impish Finn, who look as comfortable in the forest as Jamie Oliver does in his polished stainless steel kitchen. “But wild foods have so much life.”

All morning, we’ve been combing the coastal meadows and grassy, boulder-strewn slopes of Seurasaari island, an open-air museum of traditional log houses on a patch of peaceful land linked by a bridge to the mainland. Anna’s wicker basket is heaving with goodies: wild pansies to be frozen in ice cubes for decorative cocktails; ‘Slippery Jack’ mushrooms for a risotto; and wood sorrel, a delicious salad garnish with a bitter sherbet twang.

There aren’t many urban centres where you can pick edible herbs and mushrooms a short drive from downtown, but the Finnish capital is an exception. In a country where the right to forage and roam is ingrained in law, living from the land is a national pastime. Last month, the city scored fourth place in the world’s Global Destination Sustainability (GDS) Index. Ambitions don’t stop there; by 2030, Helsinki hopes to be carbon neutral.

Sustainability is a buzzword – and for good reason. But unconsciously it’s been a way of living for Finns for decades. This is still the most forested country in Europe (75% of the territory is covered with trees) and the population is around 5.5 million – less than half the number of people living in Greater London.

“We are forest people. It’s in our DNA to be hunter-gatherers,” says Anna, pouring a cup of chaga mushroom tea from a flask. The parasite sliced from the trunk of a birch tree, she tells me, is a prized superfood known for boosting immunity. A qualified biologist, who swapped a desk job for life outdoors, these days Anna regularly takes tourists and corporate groups on foraging tours, and enjoys watching any sense of hierarchy fade away at the forest boundaries. “Here, everyone loses their titles,” she says.

A natural contender for Europe’s most wholesome city break, Helsinki makes sustainable living look easy. At Restaurant Skörd (skö in the city’s central Design District, co-founder Janne Kylmämaa proudly tells me that everything – “except the salt” – is sourced from Finland. In a climate where little grows for three-quarters of the year, creating a gourmet menu is challenging.

“It gives room to innovate with ingredients and what’s available on the day,” says Janne, serving me with a starter of parsley root with hollandaise sauce and yarrow, in his small, simple brick-walled dining room. Mallard heart with horse radish, deer with raspberry-dusted lovage, and porcini ice cream are among the surprising highlights.

Most unexpected of all, however, are the wines, all made from berries – including a white berry wine that could easily masquerade as a Chilean sauvignon blanc. Made by a handful of enthusiasts, the wine scene is slowly growing and earlier this year the first grape wine made with grapes grown in Finland was produced – both an impressive feat and an alarming indication of climate change.

Making the most of available resources is key to living in harmony with nature – an approach adopted by circular fashion franchise Relove, who’ve transformed thrift store shopping into a boutique experience. The brainchild of former radio presenter and model Noora Hautakangas, their latest store opened in the departure lounge of Helsinki-Vantaa this summer, making it the world’s first second-hand store in an airport.

I browse rails at a concession within the Stockmann department store in Helsinki’s city centre, all rented by sellers but neatly arranged by staff. Second-hand finds from international brands like Isabel Marant and Chanel can be found alongside local champions such as Gauhar and Paola Suhonen, who only makes limited edition runs of her clothing to avoid waste.

One thing I don’t fail to do is make a trip to a sauna before leaving; it’s a Finnish tradition and one of the best ways to spend an early autumn evening. On Lonna, a tiny island in the 330-strong Helsinki archipelago, once used by the Russian navy to store mines, I visit a eco-friendly sauna and organic restaurant that belongs to Visit Finland’s Sustainable Travel Finland (STF) programme.

Later that night, on the 10-minute ferry ride back to the Market Square, I finally get a sense of what makes this understated, clean-living city so joyful. It starts with a few fingers drumming on a beer can, followed by a group of friends humming, and finally a girl climbing onto one of the leather banquettes to sing Pharrell Williams’ hit ‘Happy’. Impromptu and uplifting, it’s pure fun. And yes, I do clap along because, as the lyrics suggest, that’s what I want to do.