How to NOT get sick this winter - 3 foods to fight colds, beat flu & protect your immune system

Main Ideas

1. The immune system needs balance—not a “boost”

• The immune system includes specialized cells that move through blood and tissues, as well as ordinary body cells that can detect infection or damage and signal for help.
• Its job is not simply to react as strongly as possible. It must fight microbes without attacking healthy tissues. An overactive or misdirected response can contribute to allergies and autoimmune disease.
• Fever and a runny nose can be part of the body’s response to infection; they do not automatically mean the immune system has failed.
• The guests caution against products marketed as “immune boosters,” as their claims often go beyond the evidence. Correcting a genuine nutrient deficiency matters, but taking extra supplements when nutrient levels are normal has little evidence of preventing illness.

2. Why people respond differently

• People can have different symptoms and recovery times even after catching the same virus.
• Immune-system genes are highly diverse. There is no single “best” set: different genetic variants may help against one infection while offering less protection against another.
• Genes are only part of the picture. Previous infections, childhood exposure to microbes, environment, gut microbes, and changes in gene activity over time can also shape immune responses.
• In a study of twins discussed by Tim Spector, the frequency of colds had only a limited genetic component. The speakers also describe research suggesting that many genes change with age.
• Aging is associated with a modest rise in inflammatory signals, which may make it harder for the immune system to switch on appropriately and then return to a resting state.
• The speakers note differences between men and women in immune responses, while emphasizing that reactions vary considerably between individuals.

3. Why respiratory infections are more common in winter

• Winter brings several factors together: people spend more time indoors and in poorly ventilated spaces, and some viruses survive longer in cold conditions.
• Cold, dry air may also affect the nose and its defenses. Mucus is part of the body’s protection and contains molecules that can act against viruses.
• Simply getting cold or wet—such as going outside with wet hair—does not itself cause a cold. The discussion cites an old study in which people exposed to cold conditions did not commonly catch colds.
• Avoiding crowds can reduce exposure to germs, but the guests do not recommend withdrawing from normal social life.

4. Common claims about supplements and food

• Vitamin C: It does not prevent colds. High-dose use may be associated with slightly shorter colds, but the reported effect is small and does not establish that vitamin C is the cause.
• Vitamin D: The evidence discussed suggests, at most, a modest reduction in respiratory infections. The speakers mention UK winter guidance but do not present vitamin D as a strong shield against illness.
• Zinc and other nutrients: Supplements may matter when someone is deficient, but there is little evidence that extra amounts prevent infection in people who already have adequate levels.
• The guests criticize broad “immune support” claims on supplement labels, saying they can be permitted without strong evidence that a product improves real-world infection outcomes.
• When ill, staying hydrated is important. If appetite is low, the practical advice offered is to try to eat a little rather than force a large meal.

5. Gut health, diet, and immunity

• The gut and its microbes interact with immune cells in the intestinal lining. The relationship goes both ways, and food can influence the microbes involved.
• Some gut bacteria produce short-chain fatty acids, including butyrate. These can support regulatory T cells, which help prevent an immune response from attacking healthy tissues.
• The speakers describe a large COVID-era food-diary project in which healthier diets were associated with less severe illness, even after adjustments for other health factors. They report that the poorest diets were linked with a three- to five-times higher risk of severe COVID. This is an association from the project, not proof that diet alone caused the difference.
• Tim Spector’s three food recommendations are:
  • Eat a wide variety of plant foods, aiming for 30 different plants per week to increase fiber and plant diversity.
  • Aim for three servings of fermented foods per day.
  • Limit ultra-processed foods, which the speakers say can negatively affect the gut microbiome and immune health.

6. Five practical habits discussed

• Prioritize sleep. Sleep restriction has been linked in studies to weaker antibody responses after vaccination and changes in inflammatory markers. Tim Spector’s personal suggestions include making the bedroom dark and quiet, turning off devices before bed, and allowing more time for sleep. Individual sleep needs vary.
• Reduce prolonged stress where possible. The guests describe evidence that stress hormones such as cortisol can affect immune-cell function. Chronic stress is the concern; a brief stressful event does not mean someone will catch a cold. Mindfulness, tai chi, and walks in nature may help reduce stress, though direct experiments proving that they prevent infections are difficult.
• Eat for gut and overall health. Follow the plant-diversity, fermented-food, and ultra-processed-food guidance above.
• Exercise regularly at a manageable level. Exercise can affect immune signaling, and the greatest gains may come from people who are inactive starting to move more. The advice is to increase activity rather than push to extreme exertion; rest days may be useful. The discussion includes supportive animal research but notes that human evidence can be difficult to separate from other lifestyle factors.
• Avoid tobacco and be cautious with alcohol. The speakers describe tobacco as clearly harmful to immune function, especially in the lungs. Heavy alcohol consumption can also harm immunity; evidence about moderate consumption is less clear, and alcohol may disrupt sleep.

7. Overall takeaway

The strongest practical message is to support the immune system’s balance rather than try to “boost” it with products. Sleep, stress, diet, and exercise are useful areas to work on, but people should not blame themselves for getting sick or recovering slowly: immune responses differ naturally, and someone may be better equipped to fight one virus but not another.

The guests also recommend being skeptical of confident health claims and asking what evidence supports them.

Speakers and Sources Featured

• Unnamed host/interviewer of the ZOE episode.
• Professor Daniel Davis, immunologist at Imperial College London.
• Professor Tim Spector, epidemiologist at King’s College London and ZOE scientific co-founder.
• ZOE promotional segment: The host promotes Daily30, a ZOE product; this is advertising rather than independent expert advice.