Winter brings shorter days, lower temperatures, more time indoors in close proximity to others — and significantly more infections. Giving your immune system optimal nutritional support can mean the difference between staying well and spending weeks fighting colds. Here’s what the evidence actually supports.

Why We Get More Ill in Winter

It’s not just the cold. Vitamin D levels plummet with reduced sunlight — and Vitamin D is critical for immune function. Indoor heating lowers humidity, drying out the mucous membranes that form our first line of defence against respiratory viruses. We spend more time in enclosed spaces with other people. And certain respiratory viruses (influenza, RSV, coronavirus) survive longer and transmit more easily in cold, dry air.

Vitamin D: The Winter Priority

Public Health England recommends that all UK adults take 10mcg (400IU) of Vitamin D daily from October to April. Research (including a landmark 2017 BMJ meta-analysis of 25 randomised trials) confirms that Vitamin D supplementation reduces the risk of acute respiratory infections — particularly in those who are deficient. Most UK adults are significantly deficient by January. Higher doses (25–50mcg) may be warranted for those at greater risk. Vitamin D3 (cholecalciferol) is more effective than D2.

Zinc

Zinc is required for the development and function of virtually every immune cell. Even marginal zinc deficiency — which is common — measurably impairs both innate and adaptive immunity. 15–25mg daily (as zinc gluconate, citrate or picolinate) during winter months is sensible. Don’t take on an empty stomach. Don’t exceed 25mg daily long-term (copper absorption is affected).

Vitamin C

While Vitamin C doesn’t prevent colds in the general population, it may modestly reduce duration, and it supports multiple aspects of immune function. 200–500mg daily is sufficient — megadosing above 1000mg/day offers diminishing returns and may cause GI upset.

Selenium

UK soils are selenium-depleted, meaning UK dietary intake is consistently below recommended levels. Selenium is a cofactor for antioxidant enzymes and has been shown to support both innate and adaptive immunity. 55–100mcg daily from selenium-rich foods or supplements.

Sleep: The Highest-Yield Immune Intervention

A now-classic study (Cohen et al.) found that people sleeping less than 6 hours per night were 4.2 times more likely to catch a cold than those sleeping 7+ hours. Sleep is when the immune system consolidates its “memory” of previous infections and repairs itself. Consistent 7–9 hours per night is more effective than any supplement.

Stress Management

Cortisol (the stress hormone) is immunosuppressive at chronically elevated levels. Sustained psychological stress significantly impairs immune response. Mindfulness, regular exercise, adequate social connection, and limiting news intake all support healthier stress responses — and healthier immune systems.

Shop Immunity Supplements at Chemist 2 Customer. Related: Vitamins for Immunity, Cold & Flu Guide.