On a brisk winter morning in London, I find myself at the edge of a reservoir, feeling both insane and underdressed in swim shorts. The water temperature is a biting 3.9°C, and seasoned swimmers inform me this isn’t just cold water swimming—it’s “ice” swimming. How did I get here? I’ve been captivated by the notion of boosting the immune system.

Our immune systems are already impressive in their defense against viruses and bacteria. However, the market is flooded with supposed “immune-boosting” foods and supplements. Can these really augment our body’s defenses? Regular exercise might be the key. While studies on cold-water swimming are inconclusive, moderate exercise has been linked to fewer viral infections. Though robust clinical trials are pending, regular activity likely helps maintain a youthful immune system.

The efficacy of vitamins is debated. While a deficiency in vitamin C might harm immunity, extra intake offers little for most people. Multivitamins are often deemed needless, though some research suggests potential vitamin D benefits for those with respiratory conditions.

Your immune system is most active in the morning, becoming less so by late afternoon. Maintaining a regular daily rhythm might help enhance its effectiveness. Conversely, smoking and obesity can undermine immune health by increasing bodily inflammation, rendering us more susceptible to infections.

Stress, the underrated saboteur, elevates cortisol, which weakens the immune defense. Thus, engaging in stress-relieving activities, like socializing or even cold-water swimming, could confer benefits.

Ultimately, are there ways to supercharge our immunity beyond a healthy lifestyle? The evidence is scant. Vaccinations remain our best bet to bolster our defenses. Perhaps instead of chasing every immune-boosting trend, we should focus on preventing infections in the first place.