Kenneth Glad
Everyday health advice often promises simple answers. The reality is more measured, more personal and still developing.
Large doses of vitamin C are unlikely to stop someone catching a cold, Professor Daniel M. Davis argues in a column published in the Daily Express.
His wider point is not that immune health is unimportant, but that it is often described too simply. The language of “boosting” immunity can be misleading because a stronger immune reaction is not always the same as a better one.
The immune system has to make fine judgments constantly. It must respond to harmful viruses, bacteria and fungi, while leaving harmless food, useful gut microbes and the body’s own healthy cells untouched.
Immune advice can mislead
Davis describes immune health as a question of balance and precision. Too little protection leaves people vulnerable, but too much activity can create a different kind of danger.
That is why immune-related illness is not only about catching infections. In conditions such as multiple sclerosis, rheumatoid arthritis, lupus and type 1 diabetes, the immune system mistakenly targets healthy tissue.
Davis also referred to David Vetter, known as the boy in the bubble, as a rare but powerful example of severe immune failure.
Vetter lived in isolation because of a serious immune disorder and died aged 12 from cancer linked to a virus.
Some habits deserve attention
The professor’s warning on vitamin C cuts against a familiar household belief. He states that the nutrient is essential for health, but the claim that heavy dosing can prevent colds has little support.
Davis connected the idea’s popularity to Linus Pauling, whose public advocacy helped make vitamin C a cultural symbol of cold prevention.
The lesson, according to Davis, is that even famous scientific voices should not be treated as proof on their own.
The same caution applies to probiotics. Gut microbes can influence immunity, and probiotics can affect the microbiome, but researchers have not yet settled what a “healthy” microbiome should look like.
Lifestyle is not one-size-fits-all
Weight, movement, stress and sleep all belong in the immune discussion, but none offers a universal formula.
According to Davis, an infection risk can rise when someone is underweight as well as overweight.
Body fat is not just stored energy. It can interact with immune cells and contribute to inflammation, which helps explain why obesity may affect immune health.
Exercise is also complicated. Moderate activity appears beneficial, while extreme exertion may strain immune function in the short term, even if it can bring longer-term advantages.
Stress adds another layer. Chronic pressure can raise cortisol, a hormone that tends to quiet some immune responses.
Sleep and immunity also influence each other, making rest more than a lifestyle slogan.
New treatments focus on precision
The more promising future, in Davis’s view, lies in targeted science rather than supplement shortcuts.
He points to CAR T-cell therapy, which can involve removing a patient’s immune cells, genetically modifying them to recognize cancer, and returning them to the body.
That treatment is already used for some children with acute lymphoblastic leukaemia.
Davis says that similar immune-based approaches may later be explored for autoimmune disease.
The message is not that people can ignore everyday health. It is that immune health cannot be reduced to one pill, one food or one trend.
Source: Daily Express column by Professor Daniel M. Davis, June 1, 2026.
