Vitamin D

50–90% of US adults are deficient in vitamin D; deficiency associated with increased risk of diabetes, autoimmune diseases, and cardiovascular disease

Why It Matters for Longevity

50–90% of US adults are deficient in vitamin D; deficiency associated with increased risk of diabetes, autoimmune diseases, and cardiovascular disease Vitamin D is essential for immune modulation, calcium absorption, and cardiovascular health; acts as a steroid hormone affecting hundreds of gene expressions. Vitamin D is important for normal immune function and maintaining bone mineral density Regulates immune cell differentiation; essential cofactor for calcium absorption in bone. Deficiency in vitamin D has been implicated in brain aging and dementias Vitamin D receptors are present throughout the brain; vitamin D may have neuroprotective anti-inflammatory effects. Vitamin D supplementation reduces all-cause mortality in meta-analysis of 50 RCTs; strongest effect in those with baseline deficiency (PubMed) Low serum 25(OH)D levels independently associated with cognitive decline and Alzheimer's disease risk in longitudinal studies (PubMed)

How to Use It

Pairs well with fatty fish, egg yolk, fortified plant milk. Use as a nutrient in your daily meals according to the Longevity Diet guidelines.

What to Pair It With

Synergies

• Calcium (synergy): Vitamin D is required for intestinal calcium absorption; deficiency nullifies calcium supplementation - Zinc (synergy): Both vitamin D and zinc support immune function; often co-deficient - Multivitamin (complement): Book recommends taking vitamin D within a multivitamin every 2–3 days to avoid toxicity risk

Flavor Profile

Category: supplement.

The Science

• PubMed: Vitamin D supplementation reduces all-cause mortality in meta-analysis of 50 RCTs; strongest effect in those with baseline deficiency - PubMed: Low serum 25(OH)D levels independently associated with cognitive decline and Alzheimer's disease risk in longitudinal studies - Book claim (high confidence): 50–90% of US adults are deficient in vitamin D; deficiency associated with increased risk of diabetes, autoimmune diseas - Book claim (high confidence): Vitamin D is important for normal immune function and maintaining bone mineral density

Key Nutrients