The Longevity Nutrients Glossary: Every Key Micronutrient, What It Does, and Optimal Levels
A comprehensive reference guide to the micronutrients most relevant to longevity — their biological roles, optimal ranges, deficiency signs, best dietary sources, and supplementation guidance. This is the nutrition reference companion to the complete testing guide in article 1.9.
- Micronutrient insufficiency — nutritional status below optimal for longevity despite being above the clinical deficiency threshold — is pervasive in modern populations and rarely assessed. The most commonly insufficient micronutrients in health-conscious adults are vitamin D, magnesium, zinc, omega-3 fatty acids, vitamin K2, and B vitamins (particularly B12 in older adults and vegans).
- The distinction between RDA (designed to prevent deficiency in 97.5 percent of a healthy population) and optimal intake for longevity is critical. The RDA for vitamin D (600-800 IU/day) maintains 25-OH-D above 20 ng/mL in most people — but the optimal longevity range of 40-60 ng/mL requires 2-4x the RDA for most adults. Similar gaps exist for magnesium, zinc, and omega-3.
- Fat-soluble vitamins (A, D, E, K) require dietary fat for absorption and can accumulate to toxic levels with excessive supplementation — particularly vitamins A and D. Water-soluble B vitamins and vitamin C are generally self-limiting via renal excretion at high doses, with notable exceptions (B6 toxicity causes peripheral neuropathy at doses above 100-200 mg/day for extended periods).
- The synergistic micronutrient relationships most important for longevity: vitamin D and K2 (D promotes calcium absorption; K2 directs it to bone, not arteries); zinc and copper (competitive absorption requires balanced intake); magnesium and vitamin D (magnesium is required for vitamin D activation); folate and B12 (both required for homocysteine remethylation; B12 deficiency produces functional folate deficiency).
- Testing strategy: test before supplementing. 25-OH vitamin D, serum zinc, RBC magnesium, omega-3 index, homocysteine (as a functional folate and B12 marker), and serum B12 are the highest-yield micronutrient tests for longevity-oriented adults. Do not supplement without knowing baseline status — over-supplementation carries real risks for fat-soluble vitamins and some minerals.
Micronutrients — vitamins and minerals required in small amounts for specific biochemical functions — are the most overlooked component of nutritional longevity. While macronutrient debates (protein vs fat vs carbohydrate) generate the majority of nutrition discourse, the micronutrient gaps that impair enzymatic function, DNA repair, immune competence, and mitochondrial efficiency in a substantial fraction of adults receive relatively little attention. This glossary provides reference-quality information on the micronutrients most relevant to longevity.1
The Essential Longevity Micronutrients
Vitamin D (25-hydroxyvitamin D): Optimal: 40-60 ng/mL. Functions: calcium absorption, immune regulation, muscle function, gene expression regulation (via nuclear VDR receptor). Deficiency signs: fatigue, muscle weakness, frequent infections, bone pain. Primary sources: sun exposure, fatty fish, fortified foods. Supplementation: D3 (cholecalciferol) 1,000-4,000 IU/day with K2 co-supplementation above 2,000 IU. Test 3 months after starting supplementation to confirm adequate response.
Magnesium: Optimal: RBC magnesium in upper half of reference range; dietary intake 400-600 mg/day elemental. Functions: cofactor for 300+ enzymes, ATP synthesis, DNA repair, insulin receptor signaling, neuromuscular function. Deficiency signs: muscle cramps, poor sleep, anxiety, constipation, elevated blood pressure. Primary sources: leafy greens, nuts, seeds, legumes, dark chocolate. Supplementation: magnesium glycinate or malate 200-400 mg/day elemental. Note: serum magnesium is insensitive; RBC magnesium is preferred for functional status assessment.2
Zinc: Optimal: plasma zinc in upper half of reference range; dietary intake 11-15 mg/day. Functions: immune cell development, DNA synthesis, taste and smell, wound healing, testosterone synthesis, insulin storage. Deficiency signs: frequent infections, poor wound healing, taste disturbances, hair loss, diarrhea. Primary sources: oysters (highest), red meat, shellfish, legumes, nuts. Supplementation: zinc glycinate, acetate, or citrate 8-15 mg elemental/day; always include copper (1-2 mg/day) when supplementing zinc above 15 mg/day.
Vitamin K2 (Menaquinone-7, MK-7): Optimal: 100-200 mcg/day MK-7. Functions: carboxylation of osteocalcin (directing calcium into bone) and matrix Gla protein (preventing arterial calcium deposition). Deficiency signs: generally asymptomatic until measurable via functional tests (ucOC ratio). Primary sources: natto (highest), fermented cheese, some fermented vegetables. Supplementation: MK-7 form (trans-isomer, half-life 72 hours) 100-200 mcg/day with food. Essential co-supplement when taking vitamin D above 2,000 IU/day.
Omega-3 Fatty Acids (EPA and DHA): Optimal: omega-3 index above 8 percent. Functions: structural membrane lipids in brain and heart, precursors to anti-inflammatory eicosanoids and specialized pro-resolving mediators, retinal function (DHA). Deficiency signs: dry skin, poor concentration, mood disturbances. Primary sources: fatty fish (salmon, sardines, mackerel), algae oil (plant-based DHA). Supplementation: 1-3 g EPA+DHA/day from fish or algae oil; measure omega-3 index before and after supplementation to confirm adequate response.3
B12 (Cobalamin): Optimal: serum B12 above 400 pg/mL; homocysteine below 9 umol/L as functional marker. Functions: DNA synthesis, myelin formation, red blood cell production, homocysteine remethylation. Deficiency signs: fatigue, peripheral neuropathy, megaloblastic anemia, cognitive impairment, elevated homocysteine. At-risk populations: vegans and vegetarians (no dietary B12), adults over 60 (reduced intrinsic factor), metformin users (reduced B12 absorption), PPI users. Supplementation: methylcobalamin 500-1,000 mcg/day; sublingual or injectable forms bypass IF-dependent absorption in severe deficiency.
Folate (Vitamin B9): Optimal: RBC folate in upper normal range; plasma homocysteine below 9 umol/L. Functions: DNA synthesis, methylation cycle (via 5-MTHF), neural tube development. As covered in article 3.12, supplement with methylfolate (5-MTHF) rather than folic acid in people with MTHFR variants. Dietary sources: leafy greens (the name comes from folium, Latin for leaf), legumes, liver. Supplementation: 400-800 mcg/day of 5-MTHF form.
Selenium: Optimal: plasma selenium 120-150 ug/L. Functions: selenoprotein synthesis (glutathione peroxidase, thioredoxin reductase, deiodinases — the thyroid enzymes). Deficiency signs: muscle weakness, thyroid dysfunction, impaired immunity, elevated oxidative stress. Primary sources: Brazil nuts (highest and variable — 2 per day provides adequate selenium), seafood, meat. Supplementation: selenomethionine 100-200 mcg/day; avoid excessive supplementation (above 400 mcg/day) due to toxicity risk.4
Iodine: Optimal: urinary iodine excretion 100-200 ug/L (population measure; individual testing is urinary iodine concentration). Functions: thyroid hormone synthesis (T4 requires 4 iodine atoms; T3 requires 3). Deficiency: the most common cause of preventable intellectual disability worldwide; in developed countries, iodine deficiency can occur in people avoiding iodized salt and dairy. Primary sources: iodized salt, seafood, dairy. Supplementation: generally not needed if using iodized salt; kelp-based supplements can cause hyperthyroidism and are not recommended for routine supplementation.
References
- 1Ames BN. "Optimal micronutrients delay mitochondrial decay and age-associated diseases." Mechanisms of Ageing and Development. 2010;131(7-8):473-479. [PubMed]
- 2Rosanoff A, et al. "Suboptimal magnesium status in the United States: are the health consequences underestimated?" Nutrition Reviews. 2012;70(3):153-164. [PubMed]
- 3Harris WS. "The omega-3 index: clinical utility for therapeutic intervention." Current Cardiology Reports. 2010;12(6):503-508. [PubMed]
- 4Rayman MP. "The importance of selenium to human health." Lancet. 2000;356(9225):233-241. [PubMed]