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Experts debunk winter immune-boosting myths and reveal what actually works
As winter approaches, the hunt for remedies to ward off colds and flu intensifies-from cold water swimming to fermented drinks-but immunologists warn most popular trends lack scientific backing.
Cold water swimming: adrenaline over immunity
Cold water swimming has gained traction as a supposed immune booster, with enthusiasts claiming it prevents seasonal illnesses. However, Professor Eleanor Riley, an immunologist, clarifies that while white blood cell levels temporarily spike post-swim-triggered by adrenaline and endorphins-this effect fades within hours. "Your body hasn't actually produced more cells," she told BBC Radio 4's Inside Health podcast.
Riley notes the real benefit may stem from social connection. "Feeling brighter, more alert, and connected has physiological effects," she says, though similar benefits could come from activities like running or dancing.
Fermented drinks and the microbiome: weak evidence
Kombucha and other fermented drinks are marketed as microbiome enhancers, but experts remain skeptical. Dr. Margaret McCartney, a GP, acknowledges theories linking microbiome diversity to immunity but stresses: "We lack strong real-world evidence to recommend kombucha." Professor John Tregoning, a vaccine immunologist, adds that while the microbiome shifts during infections, it typically reverts afterward.
Vitamins: limited impact, except for D
Vitamin C and multivitamins, often touted as winter essentials, show little proof of effectiveness. "They give you expensive urine," says McCartney. Vitamin D is an exception-theoretical evidence suggests it may reduce respiratory infections in deficient individuals with pre-existing conditions. Tregoning advises sunlight exposure and outdoor activity to naturally maintain levels.
Nasal sprays and trendy shots: no immune boost
Turmeric shots, ginger drinks, and fancy nasal sprays offer no proven immune benefits, per McCartney. Tregoning explains that saline sprays (salt and water) can ease congestion by thinning mucus but don't enhance immunity.
The only proven defense: vaccination
All three experts agree: vaccination is the sole intervention that reliably strengthens immunity. Riley recommends the flu jab, which takes 7-10 days to become effective. For general support, they advise avoiding smoking, maintaining a healthy weight, prioritizing sleep, and reducing stress-alongside handwashing and ventilation to cut infection risks.
"Suppressing stress, sleeping well, and not smoking-these are the foundations. The rest is mostly noise."
Professor Eleanor Riley, immunologist
