Operation brief freeze

From blood sugar control to mental health and brain cell benefits, research suggests an icy plunge may be a fad that floats.

- JANE CLIFTON

Historians can't pinpoint when humans first learnt to swim, but 100,000 years since the possible first buoyant immersion, scientists are now toiling to determine whether a bracing dip is a magic bullet for human health.

Though sceptics deride the social-media rebranding of swimming in the sea, lakes and rivers as "wild" or "cold", more and more research suggests the growing trend for cold water immersion (CWI) triggers a set of extremely beneficial reactions in the body.

At the very least, CWI can slash one's power bills. Dougal Dunlop, 70, can chart how his daily swims in Wellington's never-temperate Oriental Bay have over the years have made him near-immune to the cold. "I don't need to turn the heater on," he says, and laughs at the idea of wearing a wetsuit for swimming, even in midwinter.

Rachel Averill, his friend in the Washing Machines sea swimming group he leads, agrees. "I'll be in short sleeves in the office when everyone else thinks it's freezing."

The growing popularity of wild swimming could also reduce New Zealand's alarming incidence of drowning. With fewer schools having access to pools to teach children swimming, the growing availability of well-organised local sea swimming groups might be able to close the gap. Washing Machines welcomes children, who swim under the supervision of grown-ups, including Dunlop, who is a professional swimming coach.

But it's the metabolic and other physical effects of CWI that have turbocharged its popularity. Pure logic suggests swimming is a healthy activity and demonstrably makes people feel good. But a recent deep dive into the known science of mammalian thermal adaptation by respected science authorities has generated extra excitement that CWI could be a fearsome weapon against diabetes, heart disease, depression, auto-immune conditions, menopause symptoms, inflammation and much else.