Vitamin D as a Shield against Aging

“

TL;DR

This narrative review examines how vitamin D acts as a geroprotective agent by counteracting immunosenescence and inflammaging through multi-target molecular mechanisms, including regulation of NF-kB signaling, modulation of T cell subsets (Th17/Treg balance), and enhancement of antimicrobial peptide production. The paper highlights that vitamin D deficiency is a pandemic condition particularly detrimental in the elderly, where it accelerates age-related declines in immune function, skeletal muscle, and cardiac tissue. The clinical significance lies in the potential for vitamin D supplementation to improve quality of life in aging populations, though the authors note that standardized guidelines for assessment and supplementation remain lacking.

Full summary

4,375 CHARS

**Background:** The aging process involves gradual functional decline at cellular and molecular levels, including mitochondrial dysfunction, epigenetic alterations, telomere shortening, and aberrant intracellular signaling. Two key drivers of aging are immunosenescence (decline in immune function) and inflammaging (chronic low-grade inflammation). Vitamin D, a steroid hormone with pleiotropic effects beyond bone metabolism, is recognized as a nutrient capable of modulating these aging processes. This narrative review aims to provide an overview of the cellular biomechanisms and biomolecules engaged in immunosenescence and inflammaging as biotargets for vitamin D interventions.

**Methods:** This is a narrative review synthesizing evidence from in vitro studies, animal models, and human clinical investigations on vitamin D's effects on immune function, cellular senescence, and age-related tissue dysfunction. The review focuses on molecular pathways including NF-kB signaling, vitamin D receptor (VDR) interactions, and effects on immune cells (T cells, B cells, dendritic cells, macrophages, monocytes) and non-immune cells (cardiomyocytes, skeletal muscle cells).

**Key Results:** The paper reports that vitamin D exerts geroprotective effects through multiple mechanisms: (1) It strengthens host defense by inducing antimicrobial proteins (AMPs) such as cathelicidin (LL-37/hCAP-18), defensins, and hepcidin, with clinical studies on tuberculosis, sepsis, viral infection, peritonitis, and pneumonia documenting that vitamin D supplementation increases serum cathelicidin and correlates with improved clinical outcomes. (2) Vitamin D counteracts inflammation by inhibiting TLR2, 4, and 9 expression and signaling, reducing production of TNF-α, IL-6, IL-23, and IL-1, and repressing T cell-recruiting chemokines. (3) It inhibits CD4+ and CD8+ T cell proliferation, particularly Th1 cells, counteracting release of IL-2, IFNγ, IL-6, IL-8, IL-12, and TNFα. (4) Vitamin D downregulates the proinflammatory Th17 cell subset while enhancing Treg cells and anti-inflammatory cytokines IL-4, IL-5, IL-10, and CCL2. (5) At the molecular level, vitamin D/VDR signaling targets NF-kB through physical interaction between VDR and IKKβ, enhanced by vitamin D, resulting in IκBα stabilization and impaired p65/p50 nuclear translocation. (6) Vitamin D delays cellular senescence through longer telomere lengths, increased antioxidant effects via Nrf2 transcriptional regulation, decreased oxidative stress and DNA damage, downregulation of p16, p53, and p21, and upregulation of Bmi1. (7) In cardiac cells, vitamin D/VDR signaling acts as a negative regulator of NLRP3 inflammasome oligomerization/activation and IL-1β release, inhibiting pyroptosis. (8) In skeletal muscle, vitamin D counteracts atrophy by interfering with Src/ERK1/2/Akt/FOXO3 signaling, limiting oxidative stress and ROS generation, and activating the Nrf2-Keap1 antioxidant pathway.

The paper notes that vitamin D deficiency (below 25 nmol/L) is common among community-dwelling elderly and very common among institutionalized elderly. It also cautions that overcorrection of vitamin D status may negatively impact skeletal muscle cell metabolism, similar to antioxidant overdose.

**Clinical Implications:** The authors recommend supplementation of about 20 µg vitamin D (800 IU) per day for people over 70, with 50 µg/day as the safe upper level, and 600 IU for those aged 1-70 years. Supplementation with 20 µg vitamin D and 1000-1200 mg calcium increases vitamin D levels, suppresses secondary hyperparathyroidism, and improves bone and muscle strength. However, the paper identifies critical gaps: lack of universally accepted standards for vitamin D assessment, variability in measurement methods, absence of clarity in vitamin D status definitions based on standardized reference ranges, and insufficient translation of research into clinical practice. The ongoing DO-HEALTH multicenter clinical trial (2157 community-dwelling European adults aged 70+) combining vitamin D (2000 IU/day) with omega-3 fatty acids (1000 mg/day) and physical activity (30 min, 3 times/week) is expected to help implement clinical practice. The authors conclude that more accurate basic and clinical human research is necessary to approach vitamin D status determination and develop personalized treatment strategies.