How do I strengthen my weakening immune system?
Probiotics, reducing saturated fat and stress reduction have the best evidence base for supporting your immune system, although the level of certainty varies by approach and fully conclusive proof in humans is still lacking.
Probiotics (live bacteria such as lactic acid bacteria and bifidobacteria) are currently the best-supported daily intervention. They strengthen the gut barrier, alter the composition of the gut microbiome and activate immune receptors in the gut wall. Multiple studies show therapeutic potential, although the exact mechanisms in humans have not yet been fully worked out. The gut is closely connected to the immune system: a disrupted gut microbiome is associated with a poorer immune balance, though the strongest evidence for this comes from animal research.
Chronic stress is a concrete factor that undermines your immune defences. Mouse studies show that persistent stress throws the immune system off balance in a way that favours inflammation and weakens control over malignant cells. Whether psychological interventions also improve immune function in a clinically meaningful way has not been convincingly demonstrated in humans, but measurable immune changes during mental stress have been described.
Excess body weight and a high intake of saturated fats (in particular palmitic acid) cause a smouldering, low-grade inflammation that disrupts the healthy immune balance. This effect operates through multiple inflammatory pathways in immune cells and raises pro-inflammatory markers in the blood. A lean body weight and a lower intake of saturated fat in your diet help to keep this in check.
Short-term fasting (16 hours) enhanced the activation of tumour-targeting immune cells in both mice and a small group of cancer patients receiving immunotherapy. However, this result has only been studied in a cancer setting; what it means for normal immune function in healthy people is unknown. Do not yet translate this into a lifestyle recommendation for daily use.
The claims are based on one review article on probiotics (PMID 23037511), one study on the gut microbiome and neurology (PMID 40804450), one study on short-term fasting in cancer patients (PMID 41720105), one mouse study on chronic stress (PMID 39630109), one study on psychosocial factors and immunity (PMID 2657967) and one mechanistic study on palmitic acid in obesity (PMID 31363792). The maternal infection study (PMID 27540164) is not relevant to the question posed and has been excluded from consideration.