Micronutrients are fundamental to the immune system because they support barrier integrity, cellular development, signaling, and antioxidant defenses. Authoritative reviews and fact sheets from the Office of Dietary Supplements National Institutes of Health describe how specific vitamins and minerals contribute to innate and adaptive immunity and why maintaining adequate status matters for infection resistance and recovery.
Key micronutrients and supporting evidence
Vitamin D regulates antimicrobial peptide production and modulates inflammatory responses. Adrian R. Martineau Queen Mary University of London led a large meta-analysis published in the BMJ showing that vitamin D supplementation reduced the risk of acute respiratory infections, with the strongest benefit in people who were deficient at baseline. Vitamin C participates in leukocyte function and antioxidant protection; Harri Hemilä University of Helsinki has summarized randomized trial evidence that vitamin C can shorten the duration of common colds and may reduce incidence in physically stressed populations, particularly when dietary intake is low. Zinc is required for lymphocyte development and innate antiviral responses; the Office of Dietary Supplements National Institutes of Health explains that zinc deficiency impairs immune cell function and that short-term therapeutic zinc can reduce the duration of some viral illnesses when started early. Selenium supports selenoproteins that protect cells from oxidative damage and influence viral pathogenicity; Margaret P. Rayman University of Surrey has published reviews linking low selenium status to poorer immune responses and worse outcomes in certain infections.
Other essential micronutrients include vitamin A, which maintains mucosal barriers; B6, B12, and folate, which are involved in lymphocyte proliferation and signaling; and iron and copper, which are required for cellular respiration and pathogen-killing mechanisms. The Office of Dietary Supplements National Institutes of Health provides nutrient-specific summaries outlining these physiological roles and the consequences of deficiency.
Causes of deficiency, consequences, and practical considerations
Deficiencies arise from limited dietary diversity, malabsorption, chronic disease, age-related changes, pregnancy, and environmental factors. For example, vitamin D deficiency is more common at high latitudes, in people with darker skin, and among those with minimal sun exposure. Selenium status reflects soil concentrations, creating geographic differences in population intake that affect local health risks. Nutrient shortfalls can lead to increased susceptibility to infections, slower recovery, and in severe cases, higher morbidity—vitamin A deficiency remains a leading factor in childhood blindness and increased infectious mortality in some low-income regions.
Supplementation can correct deficiency and improve immune outcomes in specific contexts, but excess intake carries risks. Hypervitaminosis A or D can be toxic, and chronic high-dose zinc can cause copper deficiency; these risks are emphasized by guidance from the Office of Dietary Supplements National Institutes of Health. Clinical decisions about testing and supplementation are best made with healthcare providers who can consider age, pregnancy, comorbidities, diet, and local environmental factors. Cultural foodways and territorial resources influence both risk and strategy: community-level interventions, fortification programs, and dietary counseling tailored to regional diets often achieve better, more sustainable improvements in micronutrient status than isolated supplement use.