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Vitamin D for runners: what's being used and what the research says

We report what runners are using and what the research says. We don't recommend taking any supplement. Talk to your GP or a registered sports dietitian before trying one.

Quick answer

Research suggests it doesn't. In a meta-analysis of 13 trials in athletes, none of the seven that tested performance found a benefit, even when low levels were corrected[1]. Sports bodies class vitamin D as a supplement for low status, not a performance aid[2][3]. The NHS says everyone should consider 10 micrograms a day in autumn and winter[4].

Research
Weak (proposed)For running performance: trials found no gain, even when low levels were raised to normal.
Proposed by our editor; not yet confirmed by an expert reviewer.
WADA status
Permitted
Distances in the research
800 m–5K: limited research10K–half: not studiedMarathon: not studiedUltra: limited research

What is vitamin D?

Vitamin D is a fat-soluble vitamin that works like a hormone. The body makes most of it from sunlight on the skin, and food provides only small amounts[4][2]. The NHS lists oily fish, red meat, egg yolks and fortified foods such as some fat spreads and breakfast cereals, and notes that UK cows' milk is generally not fortified[4]. The Australian Institute of Sport (AIS) says even foods rich in vitamin D generally provide only about 40 to 150 IU a serving[2].

Supplements contain vitamin D3 (colecalciferol), the form the skin makes, or vitamin D2 (ergocalciferol), which comes from plants; the NHS says most vitamin D you can buy is one of the two[5][2]. A 2012 meta-analysis found D3 raised blood levels more than D2, though the difference was lost with daily doses[6]. The AIS says D3 is now considered preferable, and lists vitamin D in Group A as a medical supplement rather than a performance supplement[2].

Products include tablets, capsules, a syrup and oral drops[7]. Labels use micrograms or international units (IU): 1 microgram is 40 IU, so 10 micrograms is 400 IU[4]. Blood tests measure 25-hydroxyvitamin D, written 25(OH)D, in nmol/L or ng/mL, where 2.5 nmol/L equals 1 ng/mL[2].

Also called: vitamin D3, colecalciferol, cholecalciferol, vitamin D2, ergocalciferol.

Why is vitamin D getting attention?

Low levels are common in athletes. A 2022 meta-analysis of 51 studies and 5,456 elite athletes found levels below 50 nmol/L in 30% of adults and 39% of adolescents, and called these figures conservative because few studies were done in winter[8]. An earlier meta-analysis, using a higher cut-off of 80 nmol/L, found low levels more often in the UK, in winter and spring, and in indoor sports[9].

In the UK, the NHS says that between October and early March we do not make enough vitamin D from sunlight[4]. Among British Army recruits, only 9% of men and 36% of women had levels of at least 50 nmol/L in winter[10]. Public Health England reported low blood levels in 23% of adults aged 19 to 64 in its 2008 to 2012 diet survey, which it said is not the same as being deficient[11].

Many runners take it. In 135 US collegiate cross-country runners, 34% used vitamin D, including 49% of those with a past bone stress injury against 19% of those without[12]. In a survey of recreational distance runners, use ranged from 26% of 10 km runners to 3% of marathon and ultra runners, among the 84 of 119 runners included in that analysis[13]. A review says doses in elite sport range from 1,000 IU a day to 100,000 IU once a week[14].

The claims, checked against the research

  • Faster race timesNot supported

    Trials haven't found this. In a meta-analysis of 13 trials in 532 athletes, none of the seven that tested performance found a significant benefit[1], and a 2025 network meta-analysis found no significant effect on endurance performance[15].

  • Faster times when levels are lowNot supported

    Correcting low levels didn't help. In 137 male British Army recruits in winter, vitamin D3 or simulated sunlight brought 97% to at least 50 nmol/L, but 1.5-mile run times did not improve[10].

  • A higher VO2maxMixed

    Small trials disagree. In recreational runners and non-runners, 2,000 IU a day for 8 weeks raised vitamin D levels but did not change VO2max; its control groups took no supplement rather than a placebo[16]. In 28 active young men with low levels, a placebo-controlled but non-randomised trial found 6,000 IU a day for 8 weeks raised VO2max on a cycling test[17].

  • Stronger legs and more powerMixed

    A 2024 meta-analysis of 10 trials in athletes, none of them runners, found no significant overall effect on strength but a gain in quadriceps strength[18]. The IOC calls the muscle-function evidence equivocal[3].

  • Quicker recovery after hard runsMixed

    Small runner studies found lower blood markers of muscle damage after supplements[19][20], but neither measured recovery of performance. A review describes a trial in which 4,000 IU a day helped muscle force recover after damaging exercise[14].

  • Fewer stress fracturesMixed

    The trials were in military recruits, not runners, and they differ. In 5,201 female US Navy recruits, the group given calcium and vitamin D together had fewer stress fractures diagnosed during basic training than the placebo group (5.3% v 6.6%)[21]. A 2026 trial of vitamin D alone in 250 men found no clear evidence of an effect on lower-body overuse injuries[22].

  • Stronger bones in runnersMixed

    The NHS says vitamin D helps regulate calcium and phosphate, which are needed to keep bones, teeth and muscles healthy, and that everyone should consider a daily 10 microgram supplement in autumn and winter[4]. In athletes, though, studies haven't consistently linked vitamin D levels with bone health[14], and in 59 female runners, bone density didn't differ by vitamin D status[23].

How does vitamin D work?

Skin makes vitamin D when ultraviolet B (UVB) light from the sun reaches it[2]. The NHS says that from about late March or early April to the end of September most people can make all they need from sunlight, but not between October and early March[4]. One UK trial described its simulated sunlight as equal to about 15 minutes of midday summer sun, six times a week, for a casually dressed person in northern England[10].

The liver converts vitamin D to 25(OH)D, and the kidneys convert that to the active form[2]. The NHS says it helps the body take in calcium and phosphorus from food and helps the kidneys hold on to calcium[7]; these are needed to keep bones, teeth and muscles healthy[4].

Vitamin D also regulates genes in most tissues[3]. In lab studies, muscle satellite cells, which help repair muscle, carry the vitamin D receptor, but one review calls it debatable whether vitamin D has any measurable effect on muscle function in young, trained athletes[14]. The IOC says results on muscle function are equivocal, probably because studies started from different vitamin D levels[3].

Exercise itself can change blood levels: in an ultramarathon trial, 25(OH)D rose after the race in both the vitamin D and placebo groups[24].

Does vitamin D improve running performance?

No, based on the trials so far. In a meta-analysis of 13 trials in athletes, none of the seven that tested performance found a benefit, even when low levels were corrected[1]. A 2025 network meta-analysis found no significant effect on endurance performance[15]. In the clearest running test, correcting winter levels in British Army recruits did not improve a 1.5-mile run[10].

800 m to 5K (Limited research)

In a randomised trial of 137 male British Army recruits in winter, oral D3 or simulated sunlight raised vitamin D to adequate levels in 97% but did not improve a 1.5-mile (2.4 km) run[10]. In recreational runners, 8 weeks of 2,000 IU a day from October did not change VO2max, a laboratory measure rather than a race[16]. We found no trials with an 800 m, 1,500 m or 5 km race or time trial.

10K to half marathon (Not studied)

We found no trials of vitamin D with a 10 km or half-marathon result. Surveys show recreational 10 km and half-marathon runners use it[13], and across trials in athletes a network meta-analysis found no significant effect on endurance performance[15].

Marathon (Not studied)

We found no randomised trials of vitamin D that tested marathon performance. One small non-randomised study gave 21 amateur runners with low levels D3 or placebo for 8 weeks before a marathon, and measured blood markers; race time was not analysed as an outcome[20]. In the meta-analysis of trials in athletes, none that tested performance found a benefit[1].

Ultra (Limited research)

In a randomised trial of 35 male ultramarathon runners, a single 150,000 IU dose the day before a race of up to 240 km made no significant difference to split times at any checkpoint[24].

Other ultramarathon studies measured only blood markers of muscle damage[19] or bone turnover[25], not performance.

Study by study

The main studies on this page. What they took is what the study gave, not advice for any individual.
StudyWho took partWhat they tookWhat was measuredWhat they found
Farrokhyar 2017 [1]Meta-analysis532 athletes in 13 randomised trials (2005 to 2016)Oral vitamin D at a range of doses v placeboBlood 25(OH)D; physical performance tests in 7 of the trialsLevels rose, but none of the 7 performance trials found a significant effect over 12 weeks
Deng 2025 [15]Meta-analysis693 athletes in 30 randomised trials (13 on endurance)Six supplements, including vitamin D, during training v placebo or controlAnaerobic power, VO2max and endurance performanceVitamin D: no significant effect on endurance performance (SMD 0.14, 95% CI -0.51 to 0.80); very low certainty
Han 2024 [18]Meta-analysis354 athletes in 10 randomised trials, none in runnersVitamin D3 as one 150,000 IU dose, or daily or weekly doses for 4 to 12 weeks, v placeboHandgrip, bench press, vertical jump and quadriceps strengthOverall strength not significantly improved (SMD 0.18, p = 0.08); quadriceps contraction improved (SMD 0.57, p = 0.04)
Harju 2022 [8]Meta-analysis5,456 elite athletes in 51 studiesNo supplement: studies of blood levelsShare of athletes with 25(OH)D below 50 nmol/L30% of adults and 39% of adolescents; no significant difference between the sexes (8 studies)
Carswell 2018 [10]Randomised controlled trial967 British Army recruits (cohort); 137 male recruits in a randomised trial in winterPlacebo, simulated sunlight, or D3 at 1,000 IU a day for 4 weeks then 400 IU a day for 8 weeks1.5-mile run, maximum dynamic lift and vertical jumpCohort: higher levels went with faster runs. Trial: 97% reached 50 nmol/L or more, but no measure improved (P > 0.05)
Gervasi 2026 [16]Randomised controlled trial45 adults in Italy: 23 recreational runners (15 men, 8 women) and 22 non-runners2,000 IU D3 a day for 8 weeks from October, v no supplement (no placebo)VO2max, jump, isometric force and blood markersLevels rose, then fell again by March; no significant change in VO2max or jump; a trend in isometric force (p = 0.056)Funding: The supplement maker provided the films free and paid the publication fee; it had no role in the study
Mieszkowski 2021 [24]Randomised controlled trial35 male ultramarathon runnersOne 150,000 IU dose in vegetable oil, or placebo, 24 hours before a race of up to 240 kmSplit times at checkpoints; inflammatory blood markersNo significant difference in split times at any checkpoint; some inflammatory markers rose less than with placebo
Żebrowska 2020 [19]Randomised controlled trial24 ultramarathon runners2,000 IU vitamin D or placebo a day for 3 weeksBlood markers of muscle damage and inflammation after eccentric exercise25(OH)D rose; some muscle damage markers were lower, including creatine kinase at 24 hours v placebo. Performance was not tested
Weng 2026 [20]Non-randomised trial21 amateur marathon runners (16 men, 5 women) with 25(OH)D below 30 ng/mLLiquid D3 from 5,000 IU a day, adjusted to blood levels, or placebo for 8 weeks; matched, not randomised; single-blindBlood markers of muscle damage, oxidative stress and immunityLower creatine kinase and CK-MB 24 hours after the race; race time was not analysed as an outcome
Carswell 2026 [22]Randomised controlled trial250 men starting arduous military training in winterSimulated sunlight, D3 (1,000 IU a day for 4 weeks then 400 IU a day for 8 weeks) or placeboClinician-diagnosed lower-body overuse injuries over 6 months of training and 3 years of service95% reached sufficiency; no clear difference in injury risk (training HR 1.23, 95% CI 0.57 to 2.66)
Lappe 2008 [21]Randomised controlled trial5,201 female US Navy recruits2,000 mg calcium plus 800 IU vitamin D a day, or placebo, through 8 weeks of basic trainingStress fractures confirmed by X-ray or bone scan5.3% v 6.6% on placebo, 20% lower (p = 0.0026). Calcium and vitamin D were given together
Moraes 2026 [26]Meta-analysis4,183 athletes and military personnel in 15 observational studiesNo supplement: compared blood levels in people with and without stress fracturesBlood 25(OH)DLower in those with stress fractures (mean difference -5.82 nmol/L); significant in military and male groups, not in athletes or women
Wentz 2016 [23]Observational study59 female distance runners aged 18 to 40, training at 30.4°N in the USNo supplement: blood tests, bone scans and questionnaires25(OH)D, bone density and stress fracture historyAverage 122.6 nmol/L; 18.6% below 75 nmol/L; bone density and stress fracture history did not differ by vitamin D status

The key studies, in order

  1. 2008Trial5,201 female US Navy recruits: calcium plus vitamin D went with fewer stress fractures in basic training than placebo (5.3% v 6.6%). [21]
  2. 2010Observational study125 female distance runners over 2 years: higher calcium, vitamin D and dairy intakes went with hip bone density gains. [28]
  3. 2011ConsensusUS IOM: 600 IU a day (ages 1 to 70) keeps 97.5% of people at 50 nmol/L or more. Higher levels were not consistently linked to more benefit. [31]
  4. 2012Meta-analysisD3 raised blood 25(OH)D more than D2, especially as a large single dose; the difference was lost with daily dosing. [6]
  5. 2015Meta-analysis23 studies, 2,313 athletes: 56% were below 80 nmol/L. Risk was higher in the UK, in winter and spring, and in indoor sports. [9]
  6. 2016Observational study59 female runners training at 30.4°N averaged 122.6 nmol/L. Bone density and stress fracture history did not differ by vitamin D status. [23]
  7. 2017Meta-analysis13 trials, 532 athletes: supplements raised levels, but none of the 7 trials that tested performance found a benefit, even when low levels were corrected. [1]
  8. 2018TrialUK army recruits: few had adequate winter levels. In 137 men, raising levels with D3 or simulated sunlight did not improve a 1.5-mile run, strength or power. [10]
  9. 2018ConsensusMuscle-function evidence is equivocal; deficiencies should be identified before supplementing. Even vitamin products have rarely contained banned substances. [3]
  10. 2018Expert reviewNo performance benefit from raising levels far above sufficiency. Athletes at risk should be tested first; mega and bolus doses should be avoided. [14]
  11. 2019ConsensusNames five evidence-based performance supplements, not vitamin D. Allows judicious use of medical supplements for deficiencies. [27]
  12. 2020Non-randomised trial28 active young men with low levels, matched not randomised: 6,000 IU a day for 8 weeks in winter raised VO2max more than placebo. Anaerobic power did not differ between groups. [17]
  13. 2020Trial24 ultramarathon runners, 2,000 IU a day or placebo for 3 weeks: some blood markers of muscle damage were lower. Performance was not tested. [19]
  14. 2021Survey135 US collegiate cross-country runners: 34% took vitamin D, more often after a past bone stress injury. [12]
  15. 2021Trial35 male ultramarathon runners: one 150,000 IU dose the day before a race of up to 240 km made no significant difference to split times. [24]
  16. 2021SurveyRecreational distance runners (84 of 119 in this analysis): vitamin D use ranged from 26% of 10 km runners to 3% of marathon and ultra runners. [13]
  17. 2022Meta-analysis51 studies, 5,456 elite athletes: 30% of adults and 39% of adolescents had levels below 50 nmol/L. [8]
  18. 2024Meta-analysis10 trials, 354 athletes (no runners): no significant overall effect on strength; quadriceps contraction improved. [18]
  19. 2025Meta-analysis30 trials, 693 athletes: no significant effect of vitamin D on endurance performance (very low certainty). The VO2max analysis did not include vitamin D. [15]
  20. 2025Trial35 male ultramarathon runners, 150,000 IU or placebo before a race: some blood markers of bone turnover differed. Injuries were not measured. [25]
  21. 2026Trial250 men in winter military training: vitamin D raised levels but gave no clear evidence of an effect on lower-body overuse injuries. [22]
  22. 2026Trial45 recreational runners and non-runners: 2,000 IU a day for 8 weeks from October raised levels but did not change VO2max or jump height. [16]
  23. 2026Meta-analysis15 observational studies, 4,183 people: lower levels in people with stress fractures, mainly in military and male groups; not significant in athletes or women. [26]
  24. 2026Non-randomised trial21 amateur marathon runners, matched not randomised: 8 weeks of D3 went with lower muscle damage markers after the race. Race time was not analysed as an outcome. [20]

Who has the research been done in?

Most performance trials were in men: 137 male army recruits in the 1.5-mile run trial[10], and only men in the ultramarathon trial[24]. The strength meta-analysis included no runners[18], and the recreational runner trial had 23 runners, 8 of them women[16].

Starting levels matter. A review says there is no performance benefit from raising levels far above 75 nmol/L[14]. Runners who train where the sun is strong all year may already be high: 59 female runners training at 30.4°N in the south-eastern US averaged 122.6 nmol/L[23].

The findings may not apply to the runners most likely to be low. The AIS lists athletes who train indoors or early and late in the day, have dark skin, live more than 35 degrees from the equator, cover most of their body or avoid the sun[2]. Few athlete studies report skin colour, though some found low levels more often in athletes with darker skin[8]. A review notes that Black athletes often have low 25(OH)D without physiological consequences, and says that without any pathology, screening may be unnecessary and could lead to incorrect supplementation[14].

What we know about women

Research in women is thin. A meta-analysis of elite athletes found no difference between the sexes in how often levels were low, but had less evidence on women[8], and the runner trial that included women didn't analyse them separately[16]. The IAAF consensus names low energy availability as a major risk factor for bone stress fractures and says attention to vitamin D status, protein and calcium 'may also be of value'[27]. In 125 female distance runners followed for 2 years, higher dietary calcium and vitamin D went with gains in hip bone density; this was observational[28]. A meta-analysis found no significant difference in vitamin D levels between women with and without stress fractures[26]. A large trial in female Navy recruits gave vitamin D together with calcium[21].

For pregnancy, the NHS says adults need 10 micrograms a day, including pregnant and breastfeeding women, and that everyone should consider a daily 10 microgram supplement in autumn and winter[4]. Its colecalciferol pages advise a daily 400 IU supplement throughout pregnancy, note that many pregnancy multivitamins already contain 400 IU, and ask women who are trying to get pregnant, pregnant or breastfeeding to tell their doctor[29]. The 100 microgram (4,000 IU) daily limit applies to them too[4].

What the research can't tell us yet

Most running-trial participants were men[10][24]; the large trial in women studied stress fractures in Navy recruits, not performance[21]. We found no trials with a 10 km, half-marathon or marathon result.

The trials are small and varied. The 2017 meta-analysis found large differences between studies[1], and the network meta-analysis rated the endurance evidence very low certainty[15]. Several runner studies measured only blood markers, which are not performance[19][25].

Some findings are associations. In 967 recruits, higher levels went with slightly faster 1.5-mile times, about half a second per 1 nmol/L, but raising levels in the trial that followed did not improve performance[10]. The link between low levels and stress fractures also comes from observational studies[26].

Cut-offs differ, and the IOC says there is no consensus on them[3]. The Scientific Advisory Committee on Nutrition (SACN), which advises the UK government, keeps 25 nmol/L as the level below which the risk of deficiency rises, and says it is not a clinical threshold for diagnosing disease[30]. The US Institute of Medicine (IOM) set intakes to keep 97.5% of people at or above 50 nmol/L[31], while the AIS calls below 75 nmol/L insufficient[2]. How many people count as low depends on the definition used[8].

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How and when is vitamin D used in studies?

The NHS says adults need 10 micrograms (400 IU) a day, and everyone should consider a daily 10 microgram supplement in autumn and winter. It reports Department of Health and Social Care advice to take one all year for people who are not often outdoors or usually cover most of their skin, and says people with dark skin should consider one all year. It says not to take more than 100 micrograms (4,000 IU) a day unless a doctor advises otherwise[4]. SACN estimated that about 10 micrograms a day would keep 97.5% of people above 25 nmol/L in winter, without counting sunlight[30].

The AIS describes 1,000 IU of D3 a day for athletes who are at risk but not deficient, and 2,000 IU a day for 1 to 2 months after a blood test shows insufficiency[2]. The IOC describes 800 to 2,000 IU a day to maintain status in the general population, says guidelines for athletes are not yet established, and says short-term high doses for deficient athletes need careful monitoring[3].

Trials used daily doses from 400 IU to 5,000 IU or more, or a single 150,000 IU dose[10][20][24], so some research doses are above the NHS limit. In the UK, loading doses of up to 300,000 IU in total are prescription-only, for severe deficiency found on a blood test[7][32]. A review of athletes says mega doses and one-off bolus doses should be avoided[14].

When studies gave it

The NHS advice is seasonal: a supplement in autumn and winter, and a choice not to take one from late March or early April to the end of September[4]. The UK recruit trial started in January or February and ran for 12 weeks[10], and the Italian runner trial ran for 8 weeks from October to December[16].

Effects on blood levels fade: in the Italian runner trial, levels had fallen significantly in all groups 12 weeks after supplements stopped[16]. The AIS describes a repeat blood test after 1 to 2 months[2]. One trial gave a single dose 24 hours before an ultramarathon, and split times did not differ[24]. The NHS says tablets and capsules are taken with the main meal of the day[32].

What studies used. These are research protocols, not advice for any individual.
What studies usedWhenRef.
2,000 IU of vitamin D3 a day for 8 weeksOctober to December, in recreational runners[16]
1,000 IU a day for 4 weeks, then 400 IU a day for 8 weeksWinter, in army recruits[10]
A single 150,000 IU dose24 hours before an ultramarathon[24]
3,000 to 5,000 IU a dayRaised low levels in athletes (meta-analysis)[1]
5,000 IU a day, raised by 2,000 IU if blood levels stayed low8 weeks before a marathon, after lunch[20]
2,000 IU a day for 3 weeksBefore laboratory exercise tests, in ultramarathon runners[19]

What are the side effects, and who should be careful?

The NHS says taking too many vitamin D supplements over a long period can cause too much calcium to build up in the body (hypercalcaemia), which can weaken the bones and damage the kidneys and the heart[4].

The NHS says low daily doses are safe and do not normally cause side effects[7]. It lists stomach pain, feeling sick and headache as common side effects, without rates, and says vomiting, confusion, bone or joint pain or an irregular heartbeat could be signs of too much calcium[33]. It advises contacting 111 if more than 4,000 IU has been taken in 1 day[32].

Toxic blood levels are debated. The AIS cites above 375 nmol/L with raised calcium, and says the amount of supplementation that is excessive is disputed[2]; a review notes the US IoM flags levels above 180 nmol/L[14]. The European Food Safety Authority's upper level for adults matches the NHS limit of 100 micrograms a day, based on persistent excess calcium in urine at 250 micrograms a day[34].

The NHS says you cannot overdose on vitamin D through sunlight, but advises covering up or protecting the skin when out in the sun for long periods, to reduce the risk of skin damage and skin cancer[4]. The AIS says over-exposure to UVB from sunlight or tanning beds to raise vitamin D can lead to sunburn and skin cancer[2].

Medicines and health conditions

The NHS asks you to tell your doctor before starting colecalciferol if you take digoxin (too much calcium may cause an abnormal heartbeat), some water tablets such as bendroflumethiazide or indapamide, epilepsy medicines such as phenytoin or carbamazepine (a larger dose may be needed), steroids such as prednisolone (which may reduce its effects), paraffin oil laxatives or cholestyramine, antifungals such as ketoconazole, or actinomycin[35].

It says not to take other supplements containing calcium or vitamin D without talking to your doctor first[35]. It asks people with high calcium in the blood or urine, kidney problems or kidney stones, high vitamin D levels, sarcoidosis or calcification to tell a doctor first[36]. It says colecalciferol does not stop any type of contraception from working[5].

Be careful if

  • You have kidney problems, high calcium levels or sarcoidosis: the NHS asks you to tell your doctor before taking vitamin D[36].
  • You take other medicines, such as digoxin, some water tablets or epilepsy medicines: they can interact with vitamin D[35].
  • You already take a multivitamin or calcium: the NHS says not to take other supplements containing calcium or vitamin D without talking to your doctor first[35].
  • You're pregnant, trying to get pregnant or breastfeeding: the NHS asks you to tell your doctor[29].
  • You have a peanut or soya allergy, or avoid gelatine: the NHS asks people with these allergies to tell their doctor first, and notes some capsules contain gelatine[36].
  • You're thinking of high doses without a blood test: a review of athletes says those at risk should be tested before correcting low levels[14].

Is vitamin D allowed in competition?

Vitamin D is not on the World Anti-Doping Agency's Prohibited List[37]. The AIS notes it can also be given by intramuscular injection[2]. WADA's list prohibits intravenous infusions or injections of more than 100 mL in 12 hours, except those legitimately received in hospital treatment, surgery or clinical investigations[37].

The IOC notes that even common vitamin and mineral products have, rarely, been found to contain prohibited substances, and athletes are responsible for anything found in their sample[3].

Independent quality-assurance schemes, often called batch testing, check supplement products for prohibited substances[3]. WADA says using a product from one of these schemes can reduce, but not eliminate, the risk of an anti-doping violation[37], and the IOC says no product can be guaranteed entirely safe[3].

Myth or evidence?

5 things runners hear about vitamin D. Pick an answer to see what the research says.

  1. 1.Vitamin D supplements make you run faster.

    Show the answer

    Myth. Trials in athletes found no performance gain, even when low levels were corrected[1][10].

  2. 2.Low vitamin D is common in athletes.

    Show the answer

    Evidence. In a meta-analysis, 30% of adult elite athletes had levels below 50 nmol/L[8].

  3. 3.If you train outdoors in the UK, you can't be low in winter.

    Show the answer

    Myth. Between October and early March, UK sunlight isn't strong enough to make enough vitamin D[4].

  4. 4.More vitamin D is always better.

    Show the answer

    Myth. Raising levels far above normal brings no performance benefit[14], and too much can cause calcium to build up in the body[4].

  5. 5.Vitamin D is banned in competition.

    Show the answer

    Myth. It is not on the WADA Prohibited List[37].

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Frequently asked questions

Does vitamin D improve running performance?
Research suggests it doesn't: in a meta-analysis of 13 trials in athletes, none of the seven that tested performance found a benefit[1].
How much vitamin D does the NHS advise?
The NHS says adults need 10 micrograms (400 IU) a day, and everyone should consider a daily 10 microgram supplement in autumn and winter. It says not to take more than 100 micrograms (4,000 IU) a day[4].
Do runners who train outdoors get enough vitamin D in winter?
Not necessarily. The NHS says that between October and early March we don't make enough vitamin D from sunlight[4], and most UK army recruits in one study had low levels in winter[10].
Does training indoors affect vitamin D?
It can: the AIS lists training indoors, or in the early morning and late afternoon, among the risk factors for low vitamin D in athletes[2], and a meta-analysis found low levels more often in indoor sports[9].
Can I get enough vitamin D from food?
Not easily. The NHS says it's difficult to get enough vitamin D from food alone, which is why everyone should consider a supplement in autumn and winter[4]. The AIS says even vitamin D-rich foods generally provide about 40 to 150 IU a serving[2].
Is vitamin D3 better than D2?
For raising blood levels, a 2012 meta-analysis found D3 more effective than D2, although not when both were taken daily[6]. The Australian Institute of Sport says D3 is now considered the preferable form[2].
How do I know if my vitamin D is low?
Through a blood test: the NHS says your doctor will give you a blood test to find out if your levels are low[7].
What blood level counts as low?
It depends on who sets the cut-off. UK advice uses 25 nmol/L as the level below which the risk of deficiency rises[30], the US IOM aims for at least 50 nmol/L[31], and the AIS calls below 75 nmol/L insufficient[2].
Do runners with dark skin need more vitamin D?
The NHS doesn't give a higher amount, but says people with dark skin, for example from an African, African-Caribbean or south Asian background, may not make enough from sunlight and should consider 10 micrograms a day all year[4].
Does vitamin D help muscle strength?
Not clearly in athletes. A 2024 meta-analysis of 10 trials found no significant overall effect on strength, although quadriceps strength improved; none of the trials were in runners[18].
Is low vitamin D linked to stress fractures?
In military and male groups, yes; in athletes and women, the difference wasn't significant, according to a 2026 meta-analysis of observational studies[26]. A 2026 trial of vitamin D alone in 250 male recruits found no clear evidence of an effect on lower-body overuse injuries[22].
Can I take vitamin D while pregnant?
According to the NHS, yes: it says pregnant and breastfeeding women need 10 micrograms a day, like other adults[4], and its medicines pages advise a daily 400 IU supplement throughout pregnancy[29].
Is vitamin D banned in sport?
No. It is not on the WADA Prohibited List[37], though any supplement product can be contaminated[3].

References

  1. [1]

    Farrokhyar F, Sivakumar G, Savage K, et al. Effects of vitamin D supplementation on serum 25-hydroxyvitamin D concentrations and physical performance in athletes: a systematic review and meta-analysis of randomized controlled trials. Sports Medicine, 2017.

    Meta-analysis13 trials, 532 athletes: supplements raised levels, but none of the 7 trials that tested performance found a benefit, even when low levels were corrected.

    doi.org/10.1007/s40279-017-0749-4
  2. [2]

    Australian Institute of Sport AIS Sports Supplement Framework: Group A and linked fact sheets. Australian Sports Commission, 2026.

    Consensus statementLists vitamin D in Group A as a medical supplement, not a performance supplement. Says D3 is preferable; cites blood level cut-offs.

    www.ausport.gov.au/ais/nutrition/supplements/group_a
  3. [3]

    Maughan RJ, Burke LM, Dvorak J, et al. IOC consensus statement: dietary supplements and the high-performance athlete. British Journal of Sports Medicine, 2018.

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Who wrote and reviewed this

Written by Grant MacMillan, Editor, RunV. Not yet reviewed by an expert.

Last checked against its references . Next review due . How pages are reviewed · How we grade research

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