◈ Nootpedia

This page describes pharmacological agents that may have legal restrictions, side effects, and drug interactions in your jurisdiction. Information is for educational research only — consult a clinician before considering any compound.

Compact view
Research pass: thorough Compound PRIMARY-PICK HIGH

Vitamin D3

Extended Research
◈ Extended Research ◈

Our depth — beyond the mirror

Deeper analysis, verdict reasoning, and per-archetype recommendations from our research team.

▸ Editor's verdict PRIMARY-PICK HIGH

"Massive evidence base; deficiency is widespread (especially in night-owls with limited UV exposure) and clearly impairs immune function, bone density, mood, and athletic performance/recovery. For a 20yo MMA athlete training indoors, supplementation is essentially mandatory. Pair with K2-MK7 and adequate magnesium. Test serum 25(OH)D first; target 40-60 ng/mL."

Research pass: thorough
▸ Decision matrix by user profile Per-archetype
  • | Profile | Verdict | Dose target | Confidence | Notes | |---|---|---|---|---| | Dylan — 20yo MMA + business owner, indoor training, night-owl (this archetype) | PRIMARY-PICK | 5,000 IU/day + 100-180 mcg K2-MK7 + 200-400 mg Mg, titrated to 40-60 ng/mL | HIGH | Near-mandatory
    —

    indoor MMA training + late-chronotype = minimal UVB. Bone-density support for impact sport, testosterone-deficient-correction signal, immune resilience for training-illness avoidance, sleep/mood adjuncts. Test 25(OH)D quarterly until in-target, then twice yearly. Lock with V4 Mg + add K2-MK7 if not already in stack. | | Athletic male 18-35 (general) | PRIMARY-PICK | 2,000-5,000 IU/day + K2 + Mg | HIGH | Same logic, slightly less acute deficiency risk if outdoor training. Test once, titrate. | | Cognitive-focused user (deskbound, indoor) | STRONG ADD | 2,000-5,000 IU/day + K2 + Mg | HIGH | Mood/sleep/immune benefits real for the indoor user; cognitive-direct benefit is weak. Don't oversell as nootropic. | | Longevity user (40+) | STRONG ADD | 2,000-5,000 IU/day + K2-MK7 + Mg | MEDIUM-HIGH | Bone density, immune resilience, secondary signals on colorectal cancer mortality and possibly all-cause mortality (D3 sub-analyses). Pair with calcium only if dietary intake is low. K2 becomes more important with age + arterial calcification risk. | | Indoor worker / night-shift worker | PRIMARY-PICK | 5,000 IU/day + K2 + Mg | HIGH | Same as Dylan — limited UVB regardless of latitude. Cognitive + sleep signals strongest in this group. | | Dark-skinned user at >40° latitude | PRIMARY-PICK | 5,000-10,000 IU/day + K2 + Mg | HIGH | Melanin acts as a natural sunscreen, requires 5-10× longer UVB exposure for equivalent synthesis. Endemic deficiency in this group at high latitudes — supplementation essentially mandatory. | | Latitudes >40° (any skin tone) | PRIMARY-PICK Oct-April; STRONG ADD May-Sept | 5,000 IU winter, 2,000-3,000 IU summer | HIGH | Winter UVB at >40° latitude is effectively zero for D synthesis. | | Sarcoidosis / active TB / primary hyperparathyroidism | SKIP | n/a | HIGH | Hard contraindication: extra-renal CYP27B1 activity causes hypercalcemia. | | History of CYP24A1 mutation / idiopathic infantile hypercalcemia | SKIP / monitor only | <1,000 IU only with endocrinology oversight | HIGH | Inadequate inactivation = toxicity at low doses. | | History of kidney stones (calcium oxalate) | PROCEED-WITH-CARE | 1,000-2,000 IU + K2 + Mg + hydration; monitor 24-hr urinary Ca | MEDIUM | Avoid co-supplementing high calcium. Hydrate generously. | | WADA-tested athlete | PRIMARY-PICK | 5,000 IU + K2 + Mg | HIGH | Not on prohibited list; standard part of sports nutrition. |

▸ Subjective experience (deep)

Most users feel nothing acute from D3 — this is not a same-day-effect supplement. The bioactive metabolite calcitriol turns over in hours, but 25(OH)D stores rebuild over 6-12 weeks, and subjective effects (if any) follow that timecourse. Expect:

  • Weeks 1-2: Nothing perceptible.
  • Weeks 2-6: In starting-deficient users (which is most indoor-training night-owls), some report better sleep quality, less afternoon fatigue, fewer winter colds, mood lift, easier morning starts. These map roughly to the deficiency → repletion gradient.
  • Months 2-3: Subtle but real changes in immune resilience — fewer minor URTI cycles, faster recovery from training-induced micro-illness. Bone-density changes operate on a years timescale and won't be felt.
  • The unmasking phenomenon: Some users at higher doses report transient insomnia, anxiety, leg cramps, palpitations, headache — these are almost always magnesium deficiency being unmasked by rising D-dependent enzymatic demand on Mg, not toxicity. Adding magnesium glycinate 200-400 mg/day usually fixes it within days.

Dylan-specific: as a 20-year-old indoor MMA athlete who's almost certainly insufficient at baseline, the realistic effect profile is "imperceptible until week 4-8, then quiet immune + sleep gains rather than a felt boost." Don't expect modafinil-grade subjective signal. The decision to supplement is biomarker- and risk-driven, not experiential.

▸ Tolerance + cycling deep dive
  • Tolerance does not develop. D3 is a hormone-replacement pattern, not a CNS-receptor pharmacology — there's no down-regulation cycle to worry about.
  • Cycling is unnecessary and counterproductive. Serum 25(OH)D rises slowly (8-12 weeks to steady-state) and falls slowly when discontinued. "Pulse" cycling (e.g., on 3 months / off 3 months) actively dampens benefit by keeping the user in a deficiency-replete oscillation.
  • Seasonal adjustment (sensible): Northern-latitude users may safely lower the dose 1,000-2,000 IU between May and September (when UVB synthesis covers more of the requirement) and raise it back October-April. Sun-exposed equatorial users often need none. Use lab data, not the calendar, to confirm.
  • Reset / discontinuation: If discontinued, 25(OH)D falls by ~50% over 4-8 weeks. To restart, retest then resume at prior maintenance dose.
▸ Stacking deep dive

Synergistic with

  • Vitamin K2 (MK-7 form preferred; MK-4 secondary): Mandatory co-supplement at any chronic dose >2,000 IU/day D3 in this analyst's framework. K2 activates osteocalcin (carboxylated osteocalcin routes Ca to bone) and matrix Gla protein (active MGP inhibits arterial calcification). Rotterdam Study epidemiology shows highest-tertile K2 intake associated with 52% lower aortic calcification and 57% lower CV mortality vs lowest tertile. Practical dose: MK-7 90-180 mcg/day with D3.
  • Magnesium (glycinate, threonate, malate, or citrate): Cofactor for every enzyme in the D cascade. 200-400 mg/day elemental Mg. Dylan's V4 stack already contains Mg — confirm dose is in this range.
  • Boron: Modest evidence boron upregulates VDR sensitivity and reduces inflammatory cytokines in low-D states. 3-10 mg/day.
  • Omega-3 (EPA/DHA): Synergistic for inflammation modulation, sleep, mood; both fat-soluble so absorption is mutually aided when taken with fatty meal.
  • Zinc: Cofactor for VDR; modest synergy at 10-20 mg/day.
  • Vitamin A (retinol, not megadose): VDR-RXR heterodimerizes; retinol balance is real. Don't megadose A; standard dietary intake or 5,000-10,000 IU/day is fine.

Avoid stacking with

  • High-dose calcium supplements: Unnecessary in users with reasonable dairy/leafy intake; combined high-dose Ca + D without K2 raises the (controversial) cardiovascular calcification concern. If calcium supplementation is needed (e.g., post-menopausal bone-loss context, not Dylan), keep elemental Ca ≤500 mg/dose split twice daily, with K2.
  • Thiazide diuretics (without monitoring): thiazides reduce urinary calcium → raise serum Ca → potentiate hypercalcemia risk on D3.
  • Digoxin (monitor): hypercalcemia potentiates digoxin toxicity.

Neutral / safe co-administration

  • All standard biohacker stack: NAC, citicoline, alpha-GPC, creatine, beta-alanine, electrolytes, modafinil, rhodiola, ashwagandha, theanine — no interactions known.
  • Peptides (BPC-157, TB-500, Selank, Semax) — neutral.
  • Most pharma except those listed above — neutral; specifically, no interactions with SSRIs, beta-blockers, ACE inhibitors, metformin, statins.
▸ Drug interactions deep dive
  • CYP-mediated effects on D3 metabolism:
    • CYP3A4 inducers (rifampin, phenytoin, phenobarbital, carbamazepine, St. John's Wort, chronic glucocorticoids): accelerate 25(OH)D and 1,25(OH)2D inactivation via CYP24A1 upregulation. Result: faster D-depletion; users on chronic antiepileptics or glucocorticoids may need 2-3× higher D3 dosing.
    • Statins: mild theoretical concern (shared cholesterol pathway upstream of D synthesis); clinically negligible.
  • Drugs that potentiate D-toxicity / hypercalcemia risk:
    • Thiazide diuretics: reduce calciuria, raise serum Ca.
    • Calcium-channel blockers: mild theoretical effect on Ca handling.
    • Lithium: can affect Ca/PTH axis; monitor if combined.
  • Drugs whose effect changes with D status:
    • Digoxin: hypercalcemia + digoxin = arrhythmia risk.
    • Bile-acid sequestrants (cholestyramine, colestipol), orlistat: reduce fat-soluble vitamin absorption — separate by 4 hours.
    • Mineral oil, sucralfate: reduce absorption — separate by 2-4 hours.
  • No CYP induction or inhibition by D3 itself at physiological replacement doses.
  • Hormonal contraceptives: may slightly raise serum 25(OH)D via DBP elevation; no clinically meaningful interaction.
  • For Dylan specifically: no current drug interactions of concern; modafinil (V5 plan) does not interact meaningfully with D3.
▸ Pharmacogenomics

The 23andMe data Dylan will have post-June will let him interrogate several VDR and metabolism polymorphisms that meaningfully shape D-response. The 2022 Usategui-Martín meta-analysis (PMID 35057541) of 8 RCTs / 1,038 subjects nailed down two main signals:

  • FokI (rs2228570): FF genotype responds significantly better to D supplementation than Ff/ff. The F allele encodes a 3-amino-acid-shorter, more transcriptionally active VDR. Functional consequence: FF users hit target 25(OH)D on lower doses; Ff/ff users may need higher doses for equivalent biological response.
  • TaqI (rs731236): Tt+tt (variant) genotype responds better than TT.
  • BsmI (rs1544410) and ApaI (rs7975232): no significant modification of supplementation response in the meta-analysis, contradicting some older single-trial claims.

Other relevant variants:

  • CYP2R1 polymorphisms (rs10741657, rs12794714): affect baseline 25(OH)D level (slow hydroxylation = lower steady-state); large GWAS confirmed.
  • CYP24A1 polymorphisms: affect inactivation rate. Loss-of-function mutations (idiopathic infantile hypercalcemia) make standard doses dangerous; routine biohacker dosing is safe.
  • GC (DBP) polymorphisms (rs2282679): affect free vs bound 25(OH)D ratio.
  • VDR Cdx2 (rs11568820): intestinal Ca absorption efficiency.

Practical translation: Once Dylan's 23andMe data lands (June 2026), run it through Promethease or a similar interpreter to extract FokI and TaqI genotypes — these alone can move his target dose by ~30-50%. Don't wait for the genotype; start at 5,000 IU/day pre-genotype, and adjust based on the 8-12-week 25(OH)D lab, not genotype guesses.

▸ Sourcing deep dive
Path Vendor Cost Reliability Notes
Combo D3 + K2-MK7 capsules (preferred) NOW Foods, Sports Research, Thorne, Life Extension, Pure Encapsulations $0.05-0.15/day High Combo bottles standard. Dose: 5,000 IU D3 + 100-180 mcg MK-7 commonly available.
D3-only softgels (for stack-flexibility) NOW Foods, Doctor's Best, Solgar $0.03-0.08/day High Pair with separately bought MK-7 + Mg if Dylan prefers granular control.
Vegan D3 (lichen-derived) NOW Foods Plant-Based D3, Garden of Life $0.10-0.20/day High Required only if lanolin source is an issue (rare for Dylan).
Liquid D3 drops Thorne, Sports Research, Carlson $0.05-0.10/day High Useful if Dylan wants fast dose-titration without buying multiple SKUs.
Rx 50,000 IU D2 (ergocalciferol) US pharmacy, $5-15/month w/ Rx Cheap Medium D2 is less effective per IU than D3; only use if Rx-loading is preferred. Tripkovic meta says D3 superior.
iHerb / Amazon bulk Standard biohacker outlets $5-25 / 3-6 month supply High Dylan's V4 stack already sourced through iHerb. Add D3+K2 SKU at refill.

Brand-by-brand notes:

  • Sports Research D3+K2 5,000 IU + 100 mcg MK-7 — clean label, third-party tested, ~$0.10/day at refill cadence. Often Dylan's V-stack default.
  • Thorne D3+K2 liquid drops 1,000 IU + 200 mcg MK-4 — clean but uses MK-4 (shorter t½ than MK-7); preferable for users wanting micro-titration.
  • NOW Foods D3+K2 5,000 IU + 45 mcg MK-7 — cheapest tier, lower MK-7 dose may be sub-therapeutic for arterial-protection target.
  • Life Extension Super K + D3 capsule — highest-K2 tier (180 mcg MK-7 + MK-4 + K1), good for users prioritizing arterial calcification protection.

Quality flags:

  • IU labeling drift is real — third-party testing (NSF, USP, ConsumerLab) is worth it for chronic supplementation.
  • Lanolin-derived D3 (most products) is bioidentical to skin-synthesized D3 — no quality difference vs lichen-derived.
  • Avoid mega-dose 50,000 IU OTC SKUs for daily use; reserve for weekly-loading protocols if used at all.

Cost projection for Dylan's protocol: 5,000 IU D3 + 100-180 mcg MK-7 + Mg glycinate 200-400 mg = roughly $0.20-0.40/day all-in, or $75-150/year. Trivially cheap relative to peptides and Rx Modafinil in the V5 plan.

▸ Biomarkers to track (deep)
Marker When Target Rationale
Serum 25(OH)D Baseline; 8-12 weeks post-start; then quarterly until in-target; then 2×/year 40-60 ng/mL (100-150 nmol/L) — analyst-preferred; alternative bands 30-50 (Endocrine Society 2024) or 50-80 (Functional Medicine) The only direct marker of D status. Forms the backbone of titration.
Serum calcium (total + ionized) Baseline; annually 8.5-10.2 mg/dL (total) / 4.5-5.3 mg/dL (ionized) Catches hypercalcemia early — primary toxicity signal.
Parathyroid hormone (PTH) Baseline; if 25(OH)D persistently <30 or >80 ng/mL 15-50 pg/mL Elevated PTH suggests functional deficiency even if 25(OH)D borderline. Low PTH + high Ca suggests over-supplementation.
Serum phosphate Annually 2.5-4.5 mg/dL Routine; abnormalities at toxicity.
Serum magnesium (RBC Mg preferred) Baseline; annually RBC Mg 5.5-6.5 mg/dL Serum Mg is poor; RBC Mg or ionized Mg detects functional deficiency that blocks D activation.
24-hour urinary calcium Optional, especially if kidney stone history <200-300 mg/24 hr Catches early hypercalciuria from over-supplementation.
Alkaline phosphatase (ALP, bone-specific if available) Annually Standard range Elevated bone-ALP suggests osteomalacia.
Total testosterone, free testosterone, SHBG Baseline + 3-6 months post-D-replete in deficient men Total T: >500 ng/dL (Dylan: as high as feasible for athletic context) Pilz/Abu-Zaid signal: D-deficient → D-replete shift correlates with total-T rise.
CRP / hs-CRP Annually <1.0 mg/L Inflammation marker; secondary signal of D's immunomodulatory effect.
Subjective sleep, mood, training-illness frequency Daily/weekly journal n/a Captures the soft benefits that don't show on standard panels.
▸ Controversies / open debates Live debate

1. Optimal serum 25(OH)D target — 30 vs 50 vs 60-70 ng/mL.

  • Endocrine Society 2024 (Demay et al., PMID 38828931) explicitly declines to set a target and recommends against routine adult 25(OH)D testing or supplementation beyond RDA in healthy adults <75. Their reading: outside narrow indications (pregnancy, prediabetes high-risk, >75), RCT evidence does not support targeting any specific number.
  • Holick 2024 rebuttal (PMID 39486479) in Endocrine Practice: the 2024 guideline ignored extensive observational and biomarker-association data. Holick advocates 40-60 ng/mL for extraskeletal benefit and tolerance to seasonal variation, citing infection, autoimmunity, cancer-mortality signals.
  • Institute for Functional Medicine advocates 50-80 ng/mL — even higher.
  • Practical resolution for the Dylan archetype: Aim for 40-60 ng/mL — the broad-consensus band where bone benefits saturate, ARI benefits exist, and toxicity risk is essentially zero. The argument for >60 ng/mL is observational; the argument against it is the lack of upper-end RCT data. Don't chase 80+ until either RCT data improves or n=1 lab data demonstrates clear individual benefit.

2. K2 co-supplementation — required, recommended, or unnecessary?

  • Rotterdam Study (de Vlieg-Boerstoel et al., Nutrition 2004): epidemiological signal — highest-K2-intake tertile had 52% lower aortic calcification, 57% lower CV mortality, vs lowest. Observational, not causal.
  • Recent RCTs (Hasific et al. 2022 Circulation aortic valve calcification; ongoing trials): Mixed; some show K2-MK7 slows progression of pre-existing calcification, others null.
  • Mechanistic case: Strong. D3 raises intestinal Ca²⁺ absorption; without K2 to activate MGP, that Ca²⁺ can deposit where it's not wanted.
  • Practical resolution: Co-supplement K2-MK7 100-180 mcg/day with chronic D3 ≥2,000 IU. Risk is essentially zero (no toxicity in MK-7 form even at high doses; warfarin interaction is the only flag — irrelevant for Dylan). Cost is trivial. Asymmetric upside.

3. ARI / immune signal — degraded by replete-population trials.

  • The 2025 Jolliffe/Martineau pool (PMID 39993397) lost the statistical-significance threshold the 2017 IPD pool had. Critics (correctly) interpret this as evidence that the ARI benefit is real only in deficient subjects; defenders interpret it as washout from including high-replete-baseline trials.
  • Resolution: Both true. The benefit is conditional on baseline deficiency, not universal. For a likely-deficient indoor athlete like Dylan, the original protective signal still applies.

4. COVID-19 and vitamin D — Annweiler vs the field.

  • French/UK observational studies (Annweiler 2020) suggested D-replete patients had better COVID outcomes; subsequent better-controlled studies and meta-analyses largely failed to reproduce strong signals. Treat the COVID-specific case as plausible but not RCT-validated. Don't use COVID prevention as the primary justification for D3.

5. Bolus vs daily dosing.

  • Mega-dose bolus (e.g., 50,000 IU weekly or 100,000 IU monthly) raised serum 25(OH)D acutely but in Martineau's IPD subgroup analysis lost the ARI-protective effect that daily/weekly steady dosing produced. The autocrine calcitriol effects driving immune benefit seem to require sustained moderate intake, not pulses.
  • Resolution: Daily dosing wins, even if cost-equivalent and adherence-equivalent.

6. Calcium + D combo — bone benefit vs CVD risk trade-off.

  • Older meta-analyses suggested calcium + D combos might raise cardiovascular events; subsequent re-analyses largely rejected this. The signal is weak and confounded.
  • Practical: Don't co-supplement high-dose calcium without need. If supplementing calcium for bone in a deficient diet, pair with K2.
▸ Verdict change log
  • 2026-05-14 — Verdict: PRIMARY-PICK / HIGH confidence (auto-stub graduated to thorough). 5,000 IU/day + K2-MK7 + Mg, titrated to 40-60 ng/mL. Confidence is HIGH because indoor MMA + night-owl chronotype + late-spring Northern-hemisphere supplementation context produces near-certain baseline deficiency that supplementation will correct, with negligible downside. Locked into V4 stack architecture.
  • (No prior compound-file verdict.)
▸ Open questions / gaps Open
  1. FokI / TaqI genotype — Dylan's specific variant lands with the June 2026 23andMe data. Expected to inform dose calibration ±30-50%.
  2. Baseline 25(OH)D — pending the June 2026 bloodwork panel. Will calibrate starting dose (5,000 if <30 ng/mL, 2,000-3,000 if already 30-50).
  3. Mg status (RBC Mg) — V4 Mg dose is in place but functional Mg status (RBC or ionized Mg) is not yet measured. Worth adding to the June panel.
  4. Long-term arterial-calcification trajectory at 5,000 IU sustained over decades — no long-term RCTs exceed 5-10 years. n=1 monitoring via coronary artery calcium (CAC) score is overkill at 20yo but worth considering at age 35+.
  5. Whether 40-60 ng/mL or 50-80 ng/mL is the optimal Dylan-archetype target — unresolved in the literature; default to lower band until evidence improves.
  6. Bolus + ARI signal divergence mechanism — still under-mechanistically characterized. Default to daily until further evidence.
  7. Interaction with planned bromantane / selegiline (V5) — no known interactions, but D's effect on dopaminergic gene expression and selegiline's MAO-B inhibition share substrate territory in theory. Practically: neutral.

References

Manson et al. 2019 — VITAL trial vitamin D + CVD/cancer NEJM

pubmed.ncbi.nlm.nih.gov · 2019

landmark RCT, 2000 IU/day × 5 yr, null on primary endpoints, hypothesis-generating cancer-mortality signal.

View Study

Pittas et al. 2019 — D2d trial vitamin D + T2D prevention NEJM

pubmed.ncbi.nlm.nih.gov · 2019

4000 IU/day × 2.5 yr, null on incident T2D in unselected high-risk; subgroup signal in deficient.

View Study

Martineau et al. 2017 — Vitamin D + acute respiratory infections IPD meta BMJ

pubmed.ncbi.nlm.nih.gov · 2017

25 RCTs / 11,321 participants, OR 0.88 overall, strongest in baseline-deficient with daily/weekly dosing.

View Study

Jolliffe & Martineau 2025 — Vitamin D + ARI updated stratified meta-analysis Lancet Diabetes & Endocrinology

pubmed.ncbi.nlm.nih.gov · 2025

46 RCTs / 64,086 participants, OR 0.94 (CI includes 1.00), protection narrowed once replete-baseline trials added.

View Study

Demay et al. 2024 — Endocrine Society Clinical Practice Guideline JCEM

pubmed.ncbi.nlm.nih.gov · 2024

declines to set 25(OH)D target; recommends against routine testing/supplementation in healthy adults <75.

View Study

Linus Pauling Institute Micronutrient Information Center — Vitamin D

lpi.oregonstate.edu

comprehensive open-access reference.

View Source

Latest research

How was your experience with this compound?

Anonymous · one vote per session · results below at 5+ votes.

Loading…
✎

See something off?

Most of this wiki is AI-generated. Suggest a correction, dosing update, or new evidence — we review every submission.

Discussion — click to load ▸
Loading…