Vitamin D and the Athlete: Current Perspectives and New Challenges (Owens, Allison & Close 2018)
Key Findings (evidence summary)
Interest and research in vitamin D have grown sharply in the last decade and many athletes now supplement routinely, often at extreme doses
The best-established role is calcium homeostasis; in non-athletes there is a strong relationship between vitamin D and bone health
In athletes, data have consistently failed to show a relationship between serum 25(OH)D and bone health — possibly because the osteogenic stimulus of exercise dominates
Vitamin D may interact with muscle and the immune system to modulate recovery from damaging exercise and infection risk (stated as possibility, not demonstrated effect)
Toxicity: it has been argued that toxic effects appear only above 180 nmol/L 25(OH)D, but the authors' own laboratory data suggest high-dose supplementation could be problematic
Ethnicity paradox: Black athletes often present with low serum 25(OH)D without physiological consequences — possibly due to genetic differences in vitamin-D-binding protein giving more bioavailable ("free") vitamin D
In the absence of pathology, screening may be unnecessary and could lead to incorrect supplementation; thresholds should be re-examined using bioavailable vitamin D across ethnic groups
Practical Application
Owens, Allison and Close's 2018 review finds that in athletes serum 25(OH)D has not been linked to bone health, that high-dose supplementation may be harmful even below the 180 nmol/L toxicity figure often quoted, and that screening without a clinical reason may produce the wrong supplementation. Do not put an athlete on high-dose vitamin D "for performance"; the case for it rests on deficiency with a clinical reason, decided with a physician.
Any measured 25(OH)D must be read against ethnicity — a low total value in a Black athlete may not mean low bioavailable vitamin D
Muscle-recovery and immune benefits are possibilities the review raises, not effects it demonstrates; the base does not promise them
Not from this paper; the base's own practice: an athlete with a bone-stress-injury history or clear deficiency risk (winter at high latitude, indoor training, covered skin) is a reason to discuss testing with a physician, alongside energy availability (REF-341) — target ranges and doses are the physician's, not this entry's
Limitations
Narrative review; no pooled effect sizes
The abstract gives no prevalence, target range or dose figures; the entry carries none
"Optimal" 25(OH)D remains undefined, and the authors argue current thresholds may be wrong for ethnically diverse groups
Muscle and immune effects are hypothesised, not established
How this entry was checked and changed
Content correction 2026-09-27
"Insufficiency (<30 ng/mL) in 30-75% of athletes", "target 30-50 ng/mL (75-125 nmol/L) or 40-60", "1000-4000 IU/day; 50,000 IU/week", "latitude >35°", the deficient/insufficient/adequate dosing ladder (4000-5000, 2000, 1000-2000 IU/day × 3 months), "hypercalcaemia risk above 4000 IU/day" -> none in the abstract; removed.
"Screen 25(OH)D at the start of a training block" -> the abstract says screening without pathology may be unnecessary and could lead to incorrect supplementation; reversed.
"↓25(OH)D correlates with ↑stress-fracture risk" -> the abstract says athlete data consistently fail to show a 25(OH)D–bone-health relationship; removed. Added the 180 nmol/L toxicity discussion and the ethnicity / bioavailable-vitamin-D point.
Lines labelled "full text; not checked against the abstract" were checked against the open-access full text (PMC5790847): every number in them appears there; relabelled "full text, checked 2026-09-27".
2026-09-28: added Journal line from Europe PMC (PMID 29368183).