Immunosenescence refers to the progressive deterioration of immune function with age. It involves a reduction in the production of naive T cells from the thymus, reduced antibody diversity, impaired natural killer cell cytotoxicity, and a shift toward a pro-inflammatory immune phenotype characterised by chronic low-grade inflammation in the absence of specific pathogen exposure, a phenomenon called inflammageing. Diet cannot reverse these age-related changes, but it substantially determines their rate of progression and their functional consequences.
Nutritional Deficiencies That Accelerate Immune Decline
- Zinc: required for T cell development and function; deficiency is associated with impaired adaptive immune response; the most common micronutrient deficiency in older adults; eat pumpkin seeds, red meat, and legumes
- Vitamin D: modulates both innate and adaptive immunity; deficiency is associated with increased respiratory infection risk and impaired vaccine response; supplement 1,000 to 2,000 IU daily from October to March
- Selenium: required for selenoprotein enzymes that regulate immune cell function; two Brazil nuts daily provides the daily requirement
- Vitamin B12: required for DNA synthesis in rapidly dividing immune cells; declines with age due to reduced intrinsic factor production; supplement if over 65
Inflammageing and Diet
Inflammageing is driven by the accumulation of senescent cells that secrete inflammatory cytokines, chronic infection burden, gut microbiome dysbiosis, and dietary pro-inflammatory patterns. An anti-inflammatory dietary pattern directly addresses the dietary component of inflammageing by reducing the inflammatory substrate from food. Mediterranean diet adherence in older adults is consistently associated with lower levels of CRP, IL-6, and TNF-alpha, and with better maintenance of immune function markers.