The Healthspan Map · Nutrient

Vitamin D

Compiled by Aamir Malik, PhD, Professor of Neuroengineering at Brno University of Technology, from published studies. He is a researcher, not a physician. Last updated 21 August 2026.

Linked to getting too little

Where a shortfall of Vitamin D is linked: 20 sources.In the order the Map holds them: strongest evidence first. That is a statement about the evidence, not about what matters most.
Condition or system	Direction	Strength	Evidence type	What was found	Source
Anxiety	Eat enough of	Emerging	RCT / meta-analysis	Vitamin D reduces negative emotions incl. anxiety; benefit greatest in deficiency.	Cheng, Huang & Huang 2020 (opens in a new tab)
Balance & falls risk	Eat enough of	Strong	RCT / meta-analysis	In deficient older adults, 800-1000 IU/day vitamin D reduced falls ~22% (RR 0.78) via improved muscle strength and type-II fibre function.	Vitamin D & falls network meta-analysis (PMC11064304) (opens in a new tab)
Brain fog & memory	Eat enough of	Moderate	Cohort / observational	Vitamin D deficiency is associated with cognitive decline; vitamin D has neuroprotective/neurotransmitter roles (causality less established).	Mental health & micronutrients review 2024 (opens in a new tab)
Chronic fatigue / low energy	Eat enough of	Moderate	RCT / trial	In deficient adults, vitamin D3 significantly improved fatigue vs placebo (mild effect) — a deficiency-context lever, not a universal energy booster.	Vitamin D & self-perceived fatigue RCT (Nowak 2016) (opens in a new tab)
Depression / low mood	Eat enough of	Moderate	RCT / meta-analysis	Each 1000 IU/day vitamin D3 slightly reduces depressive symptoms (SMD -0.32); benefit greater in those with depression/deficiency.	Vitamin D & depression dose-response meta 2024 (opens in a new tab)
Headache & migraine	Eat enough of	Emerging	Cohort / observational	Low vitamin D status is associated with higher migraine frequency; supplementation evidence is emerging.	Food in migraine management review 2024 (opens in a new tab)
Insomnia / poor sleep	Eat enough of	Moderate	Systematic review	Serum vitamin D is inversely associated with sleep latency and daytime sleepiness; deficiency links to poorer sleep.	Micronutrient-sleep review; NHANES (opens in a new tab)
Muscle & joint pain / weakness	Eat enough of	Strong	RCT / meta-analysis	Vitamin D deficiency causes proximal muscle weakness and, via osteomalacia, bone and muscle pain; correction improves strength, especially when deficient.	Vitamin D & sarcopenia/myopathy (opens in a new tab)
Muscle & joint pain / weakness	Eat enough of	Strong	RCT / meta-analysis	Vitamin D deficiency causes proximal muscle weakness and, via osteomalacia, bone and muscle pain; correction improves strength, especially when deficient.	The effects of vitamin D on skeletal muscle strength, muscle mass, and muscle power: a systematic review and meta-analysis of randomized controlled trials, J Clin Endocrinol Metab 2014 (opens in a new tab)
Osteoporosis / low bone density	Eat enough of	Strong	RCT / meta-analysis	Vitamin D drives calcium absorption and bone mineralization; deficiency causes osteomalacia and accelerates bone loss.	Exercise + Vitamin D & BMD meta (opens in a new tab)
Peripheral neuropathy	Eat enough of	Emerging	Cohort / observational	Vitamin D deficiency is common in diabetic peripheral neuropathy and associated with more severe, subclinical nerve dysfunction.	Vitamin D & diabetic neuropathy (opens in a new tab)
Reproductive & sexual health	Eat enough of	Moderate	Systematic review	Vitamin D is positively associated with semen quality and androgen status in men and with IVF outcomes and PCOS management in women.	Vitamin D & fertility systematic review (PubMed 22275473) (opens in a new tab)
Respiratory infections & airway health	Eat enough of	Strong	RCT / meta-analysis	Vitamin D supplementation reduced acute respiratory infections, with greatest benefit in the very deficient and with daily/weekly (not bolus) dosing.	Vitamin D & acute respiratory infection IPD meta-analysis (Martineau, BMJ 2017) (opens in a new tab)
Skin, hair, nails & wound healing	Eat enough of	Moderate	Review / narrative	Vitamin D regulates the hair-follicle cycle and is associated with alopecia areata and telogen effluvium when deficient.	Vitamin D & hair follicle (opens in a new tab)
Sleep-disordered breathing	Eat enough of	Moderate	Cohort / observational	Vitamin D deficiency is highly prevalent in OSA, tracks with severity, and sustained deficiency predicted incident OSA (inflammation/oxidative-stress/airway-muscle mechanisms).	Vitamin D deficiency & incident OSA cohort (PMC12648596) (opens in a new tab)
Stress	Eat enough of	Emerging	RCT / meta-analysis	Vitamin D supplementation reduces negative emotions (depression/anxiety); benefit greatest in those deficient.	Cheng, Huang & Huang 2020, Depress Anxiety (opens in a new tab)
Thyroid dysfunction	Eat enough of	Moderate	Review / narrative	Vitamin D deficiency is far more common in Hashimoto’s/Graves’ patients and acts as an immunoregulatory factor in autoimmune thyroid disease.	Minerals & autoimmune thyroid review (PMC7574993) (opens in a new tab)
Type 2 diabetes & metabolic syndrome	Eat enough of	Moderate	RCT / meta-analysis	Low vitamin D status is associated with higher type 2 diabetes risk; supplementation in prediabetes gives modest benefit.	Diet & T2D prevention (Lancet) (opens in a new tab)
Vision problems	Eat enough of	Emerging	Review / narrative	Low vitamin D is associated with AMD and dry-eye disease among ocular micronutrient factors.	Retinal/ocular supplements review (PMC9710404) (opens in a new tab)
Weak immunity & chronic inflammation	Eat enough of	Strong	RCT / meta-analysis	Vitamin D drives antimicrobial peptides; supplementation reduces acute respiratory infections. One of the three strongest immune micronutrients.	Vitamin D & respiratory infection (opens in a new tab)

Linked to getting too much

Where an excess of Vitamin D is linked: 8 sources.In the order the Map holds them: strongest evidence first. That is a statement about the evidence, not about what matters most.
Condition or system	Direction	Strength	Evidence type	What was found	Source
Balance & falls risk	Don't overdo	Moderate	RCT / meta-analysis	High-dose vitamin D (>1000 IU/day), especially intermittent megadoses, INCREASED falls compared with 800-1000 IU/day — the both-sides U-curve.	Vitamin D & falls network meta-analysis (PMC11064304) (opens in a new tab)
Brain fog & memory	Don't overdo	Emerging	Established clinical	Severe hypercalcemia from toxicity can cause confusion and disorientation.	MedlinePlus – Hypervitaminosis D (opens in a new tab)
Digestive discomfort	Don't overdo	Emerging	Established clinical	Vitamin D excess (via hypercalcemia) causes nausea, vomiting and constipation.	NIH Office of Dietary Supplements — Vitamin D (opens in a new tab)
Endocrine & Metabolic	Don't overdo	Strong	Established clinical	Toxicity (almost always from supplements, UL 100 mcg/4,000 IU) causes hypercalcemia and hypercalciuria.	NIH ODS / MedlinePlus (Hypervitaminosis D) (opens in a new tab)
Endocrine & Metabolic	Don't overdo	Strong	Established clinical	Toxicity (almost always from supplements, UL 100 mcg/4,000 IU) causes hypercalcemia and hypercalciuria.	NIH Office of Dietary Supplements — Vitamin D (opens in a new tab)
Cardiovascular	Don't overdo	Moderate	Established clinical	Excess is associated with soft-tissue and vascular calcification and cardiac arrhythmias.	NIH ODS / IOM (opens in a new tab)
Cardiovascular	Don't overdo	Moderate	Established clinical	Excess is associated with soft-tissue and vascular calcification and cardiac arrhythmias.	NIH Office of Dietary Supplements — Vitamin D (opens in a new tab)
Liver, Kidney & Urinary	Don't overdo	Moderate	Established clinical	Vitamin D megadoses cause hypercalcemia and hypercalciuria, depositing calcium in the kidney (nephrocalcinosis) and causing injury.	Vitamin D intoxication & oxalate nephropathy (PMC12682256) (opens in a new tab)

The Healthspan Map is part of Fix the Floor, a book by Aamir Malik. About the book