How Much Vitamin D Per Day? 600-800 IU — and Why More Won't Make You Stronger

Vitamin D is the supplement people take on faith. It sits in the cupboard next to the creatine and the fish oil, gets swallowed most mornings, and almost nobody who takes it can say what it’s supposed to be doing or whether it’s working.

Here’s the short version. The Recommended Dietary Allowance is 600 IU a day for ages 1 to 70, and 800 IU from 71 onward — amounts the Institute of Medicine calculated to meet the needs of at least 97.5% of the population, and which correspond to a blood 25-hydroxyvitamin D level of at least 20 ng/mL (50 nmol/L).¹

Now the part that gets left out. Those RDAs were deliberately derived assuming minimal sun exposure, because vitamin D synthesis from UV light varies enormously and dermatologists would rather you didn’t chase it. And the same committee concluded that higher intakes “were not consistently associated with greater benefit,” that some outcomes showed U-shaped associations with risk at both low and high levels, and — bluntly — that the prevalence of vitamin D inadequacy in North America has been overestimated.¹

That was 2011. Fifteen years and several very large randomized trials later, that conclusion has aged well.

If you train seriously, the question you actually care about is narrower: does fixing a low vitamin D level make you stronger, faster, or more durable? The honest answer separates cleanly into three parts, and only one of them is a yes.

Question	Short answer
How much vitamin D per day?	600 IU (ages 1-70), 800 IU (71+) — RDA set to a 20 ng/mL blood level1
What’s the upper limit?	4,000 IU/day tolerable upper intake level1
Am I likely low?	~25% of Americans are deficient; another 41% insufficient2
What about athletes?	56% were inadequate across 23 studies of 2,313 athletes3
Will supplementing make me stronger?	No reliable effect. 11 RCTs, 436 athletes: null for strength and power4
Will it prevent fractures?	No effect in 25,871 replete adults5 — but calcium + D cut stress fractures 20% in recruits6
Can I take too much?	Yes. 10,000 IU/day for 3 years lowered radial bone density7
Should I get tested?	Not routinely, per the 2024 Endocrine Society guideline8

How much vitamin D per day do you actually need?

600 IU daily for most adults, 800 IU past 70.¹ That’s it. Those numbers are the RDA — the intake that covers at least 97.5% of the population — and they were built on bone health, because bone health is the only outcome where the evidence supported a cause-and-effect relationship firm enough to set a requirement.

The Institute of Medicine committee looked hard at everything else — cancer, cardiovascular disease, diabetes, autoimmune disease — and found the evidence “inconsistent, inconclusive as to causality, and insufficient to inform nutritional requirements.”¹ Randomized trial evidence for those outcomes was “limited and generally uninformative.”

The tolerable upper intake level is 4,000 IU per day. That ceiling matters more than most people supplementing assume, and we’ll come back to what happens above it.

One more number worth holding: the RDA targets a serum 25(OH)D of 20 ng/mL. A lot of labs, and a lot of supplement marketing, use 30 ng/mL as the sufficiency line instead. That single 10 ng/mL disagreement is why two people can look at the same blood result and reach opposite conclusions about whether it’s a problem. Keep it in mind every time you see a deficiency statistic — including the ones in the next section.

Are you actually deficient?

Probably not deficient. Quite possibly below the stricter cut.

Using data from 71,685 participants across NHANES 2001-2018, a team led by Aiyong Cui found the US picture breaks down like this:²

Serum 25(OH)D	Category	Share of US population
<25 nmol/L (<10 ng/mL)	Severe deficiency	2.6%
25-50 nmol/L (10-20 ng/mL)	Moderate deficiency	22.0%
50-75 nmol/L (20-30 ng/mL)	Insufficiency	40.9%
>75 nmol/L (>30 ng/mL)	Sufficiency	34.5%

Read that carefully. Roughly a quarter of Americans fall below the IOM’s 20 ng/mL adequacy line — that’s the real deficiency figure. The scarier “two-thirds are deficient” headlines you’ve seen come from counting everyone under 30 ng/mL, which sweeps in the 41% who are merely below a stricter threshold the IOM explicitly declined to endorse.

Deficiency isn’t evenly spread. It concentrates in women, non-Hispanic Black Americans, people aged 20-29, and in winter — with sun-protective behavior, lower BMI, lower socioeconomic status, drinking, and low milk consumption all predicting severe deficiency.² Encouragingly, the trend across 2001-2018 was mildly improving: moderate deficiency and insufficiency both declined slightly, and sufficiency rose.²

The athlete numbers are worse

Athletes are not protected by being athletic. In a systematic review and meta-analysis of 23 studies covering 2,313 athletes (mean age 22.5, 76% male), Forough Farrokhyar of McMaster University’s Department of Surgery and colleagues found 56% (95% CI 44-67%) had vitamin D inadequacy, defined as below 32 ng/mL.³

The risk factors are exactly what you’d guess, and they’re quantified:³

• Winter and early spring: risk ratio 1.85 (95% CI 1.27-2.70)
• Indoor sports: risk ratio 1.19 (95% CI 1.09-1.30)
• Latitude above 40°N: risk ratio 1.85 (95% CI 1.35-2.53), after excluding the Middle East as an outlier

Above 40°N is Philadelphia, Denver, Beijing, Madrid, and everything north. If you lift in a gym, in a northern winter, you are in three risk categories at once.

That said, don’t over-weight the indoor/outdoor split on its own. A 2023 meta-analysis by Măriuca Bârsan and colleagues pooled 5,150 athletes and found the unadjusted difference between indoor and outdoor athletes was just 3.73 ng/mL and failed to reach significance (p = 0.052). A multivariate model controlling for season, latitude, and ethnicity put indoor athletes 4.4 ng/mL lower — real, but as the authors put it, “numerically and clinically small.” Their conclusion was explicit: vitamin D status and supplementation “should not be decided based on training type alone.”⁹

Does vitamin D make you stronger?

This is the question, and the answer is the least satisfying one in sports nutrition: correcting a low level reliably fixes your blood number and does not reliably make you stronger.

Start with the dose-response, because that part works exactly as advertised. In a second meta-analysis, Farrokhyar’s group pooled 13 RCTs covering 532 athletes. Among athletes who started insufficient, at latitudes above 45°, supplementation raised serum 25(OH)D by:¹⁰

• 3,000 IU/day → +15.2 ng/mL (95% CI 10.7-19.7)
• 5,000 IU/day → +27.8 ng/mL (95% CI 16.9-38.8)

Both doses achieved sufficiency through the winter months. The pills work. Then comes the sentence that should reset expectations: of the 13 trials, seven measured physical performance, and none demonstrated a significant effect over 12 weeks of follow-up.¹⁰

A 2023 meta-analysis by Michela Sist and colleagues went at it again with 11 RCTs and 436 athletes, restricted to proper one-rep-max testing for strength and vertical jump for power. Every result crossed zero:⁴

Outcome	Standardized mean difference	p-value
Upper-body strength (baseline <75 nmol/L)	0.25 (95% CI −0.44 to 0.95)	0.47
Lower-body strength (baseline <75 nmol/L)	0.26 (95% CI −0.13 to 0.65)	0.19
Muscle power (baseline ≥75 nmol/L)	0.15 (95% CI −0.42 to 0.72)	0.61

To be fair to the other side, the evidence isn’t unanimous. An earlier 2019 meta-analysis by Li Zhang and colleagues, covering 8 RCTs and 284 athletes, found no effect on overall muscle strength (SMD 0.05, p = 0.84) or explosive power (SMD 0.05, p = 0.73) — but did find a positive effect specifically on lower-limb strength (SMD 0.55, 95% CI 0.12-0.98, p = 0.01) and in athletes training indoors (SMD 0.48, 95% CI 0.06-0.90, p = 0.02).¹¹

So the fair summary is: a possible lower-body signal in the smaller, older analysis; null in the larger, newer one. Nothing here supports vitamin D as a performance supplement. If you want the interventions that reliably move strength, they’re the boring ones — progressive overload, enough protein, and creatine, which has the evidence base vitamin D lacks for this particular job.

The same null result shows up in older adults, where you’d most expect a benefit. In a VITAL sub-study of 1,054 participants, Sharon H. Chou and colleagues at Brigham and Women’s Hospital gave 2,000 IU/day for two years and measured grip strength, walking speed, standing balance, chair stands, and Timed-Up-and-Go. There were no differences on any measure versus placebo — and Timed-Up-and-Go actually worsened slightly in supplemented participants who started with above-median 25(OH)D.¹²

Then what does vitamin D actually do for someone who trains?

Two things, with very different evidence quality.

1. Bone — but the population matters enormously.

The headline trial is discouraging if you read only the headline. In VITAL, Meryl S. LeBoff, MD, of the Division of Endocrinology, Diabetes and Hypertension at Brigham and Women’s Hospital and Harvard Medical School, followed 25,871 adults given 2,000 IU/day for a median of 5.3 years. Vitamin D did not reduce total fractures (HR 0.98, 95% CI 0.89-1.08, p = 0.70), nonvertebral fractures (HR 0.97), or hip fractures (HR 1.01). No subgroup benefited — not by age, sex, race, BMI, or baseline 25(OH)D level.⁵

But note the trial’s own stated limitation: participants “were not recruited on the basis of vitamin D deficiency, low bone mass, or osteoporosis.”⁵ It tested supplementing the already-adequate, not correcting the deficient.

Now the trial that did something closer to the latter. Joan Lappe, PhD, RN, of the Creighton University Osteoporosis Research Center, randomized 5,201 female Navy recruits to 2,000 mg calcium plus 800 IU vitamin D daily, or placebo, through basic training. The supplemented group had a 20% lower incidence of stress fractures (5.3% vs 6.6%, p = 0.0026).⁶

That’s a young, hard-training population under sudden high bone loading — much closer to an athlete starting a heavy block than to a healthy 65-year-old volunteer. It’s also calcium plus vitamin D, so you can’t cleanly credit the D alone. Still, it’s the most relevant positive result in this literature, and it points at the real mechanism: vitamin D protects bone, and bone is what breaks when you ramp training load faster than tissue adapts.

2. Aerobic capacity — association only.

In 112 male professional handball and ice hockey players, 30.4% were insufficient (<30 ng/mL) even in summer. Those with sufficient levels produced higher maximal aerobic power (3.9 ± 0.9 vs 3.5 ± 0.8 W/kg, p = 0.03), and 25(OH)D was the only independent predictor of aerobic power in the model.¹³

Read that as a flag, not a promise. It’s cross-sectional — athletes who get more sun also train differently, sleep differently, and may simply be healthier. It cannot tell you that swallowing a pill raises your watts.

Why did the big trials disappoint?

Because most of them recruited people who weren’t deficient, then tested whether more helped. It generally didn’t.

VITAL’s main result: 2,000 IU/day produced no reduction in cancer or cardiovascular disease across 25,871 adults.¹⁴ The D-Health trial reached similar conclusions in older Australians. And for respiratory infections — the claim that survived longest — the picture just shifted. A 2021 meta-analysis found a small but significant protective effect. When David A. Jolliffe of the Blizard Institute at Queen Mary University of London updated it in 2025 with six new trials, the pooled estimate across 40 studies and 61,589 participants was OR 0.94 (95% CI 0.88-1.00), p = 0.057 — the confidence interval now includes 1.00, meaning no statistically significant protection. No subgroup benefited by age, baseline status, dose size, or dosing frequency.¹⁵

This is what a nutrient looks like when it’s necessary but not therapeutic. Deficiency causes disease. Correcting deficiency fixes that. Adding more to someone who already has enough does approximately nothing — which is precisely the U-shape the IOM flagged back in 2011.¹

Can you take too much vitamin D?

Yes, and this is the part that should change behavior.

Lauren A. Burt, PhD, and colleagues at the McCaig Institute for Bone and Joint Health at the University of Calgary ran a three-year, double-blind RCT in 311 healthy adults aged 55-70, randomized to 400, 4,000, or 10,000 IU/day. The dose-dependent result went the wrong way:⁷

Daily dose	3-year change in radial bone density
400 IU	−1.2%
4,000 IU	−2.4%
10,000 IU	−3.5%

Tibial bone density showed the same pattern (−0.4%, −1.0%, −1.7%). Bone strength — failure load — didn’t differ significantly between groups, so this isn’t proof of fractures waiting to happen. But the authors’ conclusion is unambiguous: these findings “do not support a benefit of high-dose vitamin D supplementation for bone health.”⁷ More was worse for the outcome vitamin D is most famous for.

Mega-dosing has failed even more starkly. In 2,256 older women, a single annual 500,000 IU dose increased falls (rate ratio 1.15, 95% CI 1.02-1.30, p = 0.03) and fractures (rate ratio 1.26, 95% CI 1.00-1.59, p = 0.047) versus placebo, with the excess falls concentrated in the three months right after dosing.¹⁶

And clinical toxicity is now measurably rising. Reviewing 185,604 results from a Barcelona hospital between 2020 and 2025, Ana B. Fabregat-Bolufer and colleagues found annual testing grew 54.1%, median 25(OH)D drifted from 25.3 to 28.6 ng/mL, and results above 100 ng/mL more than doubled (0.14% → 0.31%). Among those very high results with calcium available, 4.3% had hypercalcemia. The paper’s title says it: Overdiagnosed and oversupplemented.¹⁷

Should you get tested?

For most people, no — and this is the recommendation that surprises people most.

The 2024 Endocrine Society Clinical Practice Guideline, chaired by Marie B. Demay, MD, of the Endocrine Unit at Massachusetts General Hospital and Harvard Medical School, reviewed the trial evidence and suggested against routine 25(OH)D testing in all populations considered — including people with obesity or dark skin — because no clinical trial evidence supported it, and no clear evidence defined an optimal target level for disease prevention.⁸

The same panel suggested against empiric supplementation above the DRI for healthy adults younger than 75. It suggested for empiric supplementation in four specific groups: children and adolescents aged 1-18, adults over 75, people who are pregnant, and those with high-risk prediabetes. And when vitamin D is indicated for someone over 50, it recommended daily dosing rather than intermittent high doses⁸ — consistent with the annual-mega-dose failure above.

None of that forbids testing. It says testing shouldn’t be routine. Reasonable cases for actually checking a level:

• A bone stress injury, or a history of them
• Malabsorption conditions, bariatric surgery, or medications affecting vitamin D metabolism
• Indoor training at northern latitude through winter, plus symptoms or a related clinical concern
• You’re already taking a high dose and want to know where you’ve landed

If you do test, the number to ask for is serum 25-hydroxyvitamin D, and the interpretation is: below 20 ng/mL is genuinely inadequate by the IOM standard; 20-30 ng/mL is a gray zone where reasonable clinicians disagree; above 30 ng/mL is sufficient by any standard in use; above 100 ng/mL warrants a calcium check.¹¹⁷

How to actually fix a low level

If you have a documented low level, the correction is straightforward and cheap.

Dose. For insufficient athletes at northern latitudes, 3,000 IU/day raised levels by about 15 ng/mL and 5,000 IU/day by about 28 ng/mL, both achieving sufficiency through winter.¹⁰ Note that both are above the 4,000 IU upper limit at the top end — which is why correcting a documented deficiency is a different activity from daily topping-up, and worth doing with a clinician rather than a guess.

Form and timing. Daily beats intermittent for anyone over 50 who needs it.⁸ Vitamin D is fat-soluble; take it with a meal containing fat.

Food. Natural sources are genuinely scarce — the Endocrine Society panel notes that because of this scarcity, adequate intake usually requires “a combination of fortified foods and supplements.”⁸ Fatty fish, egg yolks, and fortified dairy do most of the work.

Sun. Real but unreliable, and the reason the RDA was set assuming you get none.¹ Above 40°N, skin synthesis is effectively off for months.

Don’t chase a higher number. Once you’re above 20-30 ng/mL, the evidence for pushing higher ranges from absent to actively negative.⁵⁷¹⁵

While you’re auditing the cupboard, it’s worth applying the same standard to the rest of it — most recovery supplements have thinner evidence than their marketing implies, and magnesium for sleep sits in a similar honest-but-modest category.

Where this fits in a training decision

Vitamin D is a floor, not a lever. Getting off the floor matters; standing on a taller floor doesn’t help. That distinction is easy to state and surprisingly hard to hold onto when a supplement label is doing everything it can to blur it.

It also means vitamin D is not where your attention belongs on most days. The variables that actually decide whether a training block works — how much you’re lifting, how fast you’re adding load, whether you’re sleeping, whether you’re recovering between sessions — move week to week. Your vitamin D status moves seasonally, if at all.

This is the gap SensAI was built to close. A supplement label can only make a claim about a population. SensAI reads your recovery data, your training history, and your actual sessions, and turns that into the next decision — whether today should be heavy, whether the ramp you’re on is outrunning your recovery, whether the fatigue you’re feeling is a deload signal or just a bad night’s sleep. When the honest answer about a supplement is “it fixes a deficiency and otherwise does nothing,” what’s left is the training itself — and that’s the part worth instrumenting.

The stress-fracture finding is the one place these two threads meet. Bone injuries come from load applied faster than tissue adapts. Nutrition sets the ceiling on how well bone can adapt; your training load decides how hard it’s being asked to. SensAI watches the second half of that equation continuously — which is the half that changes.

Frequently asked questions

How much vitamin D should I take per day?

The RDA is 600 IU for ages 1-70 and 800 IU for 71+, set against a serum 25(OH)D of at least 20 ng/mL.¹ The tolerable upper intake level is 4,000 IU/day. Higher doses are for correcting a documented deficiency, not for daily maintenance.

Does vitamin D help build muscle?

No reliable evidence that it does. A meta-analysis of 11 RCTs in 436 athletes found no significant effect on maximum strength or power.⁴ An earlier meta-analysis of 8 RCTs found a positive effect on lower-limb strength specifically (SMD 0.55, p = 0.01) but not overall strength or power.¹¹ Correcting a deficiency is worth doing; expecting it to add muscle isn’t supported.

What is a good vitamin D level?

At least 20 ng/mL (50 nmol/L) by the IOM standard.¹ Many labs use 30 ng/mL as the sufficiency cut instead, which is why deficiency statistics vary so widely. Above 100 ng/mL warrants a serum calcium check.¹⁷

Are athletes more likely to be vitamin D deficient?

Yes. 56% of 2,313 athletes across 23 studies had levels below 32 ng/mL, with elevated risk in winter and spring (RR 1.85), indoor sports (RR 1.19), and above 40°N latitude (RR 1.85).³

Can vitamin D prevent stress fractures?

Possibly, in high-load populations. Calcium (2,000 mg) plus vitamin D (800 IU) daily reduced stress fractures by 20% in 5,201 female Navy recruits during basic training.⁶ Vitamin D alone in 25,871 generally healthy adults did not reduce fractures at all (HR 0.98).⁵

Can you take too much vitamin D?

Yes. Three years at 10,000 IU/day lowered radial bone density by 3.5% versus 1.2% at 400 IU.⁷ A single annual 500,000 IU dose increased falls and fractures in older women.¹⁶ Cases of vitamin D toxicity with hypercalcemia are rising alongside supplementation rates.¹⁷

Should I get my vitamin D tested?

Not routinely. The 2024 Endocrine Society guideline suggests against routine 25(OH)D screening in all populations it considered, citing an absence of supporting trial evidence.⁸ Testing makes sense with a bone stress injury, malabsorption, or a specific clinical concern.

Does vitamin D prevent colds and respiratory infections?

The evidence weakened. The 2025 updated meta-analysis of 40 trials and 61,589 participants found OR 0.94 (95% CI 0.88-1.00, p = 0.057) — no longer statistically significant — with no subgroup benefiting by age, baseline status, or dose.¹⁵

Do indoor athletes need more vitamin D than outdoor athletes?

Slightly lower levels, but less than you’d think. A meta-analysis of 5,150 athletes found indoor athletes about 4.4 ng/mL lower after controlling for season, latitude, and ethnicity — a difference the authors called clinically small, concluding supplementation “should not be decided based on training type alone.”⁹

The bottom line

Take 600-800 IU a day if you want the insurance; it’s cheap, safe, and matches the RDA. Get an actual blood test if you have a bone stress injury, a malabsorption condition, or a specific reason to suspect deficiency — not as an annual ritual.

If you’re genuinely below 20 ng/mL, correct it, because deficiency is real and it affects bone. If you’re above 30, adding more is not a performance strategy, and past 4,000 IU a day you’re in territory where a well-run three-year trial measured bone density going the wrong way.

The uncomfortable, useful truth is that vitamin D is a nutrient, not an ergogenic aid. The 56% inadequacy figure among athletes is a genuine public-health finding and a lousy sales pitch for a performance supplement — because the same body of research that found the deficiency also found that fixing it didn’t make anybody stronger.

Spend the attention on the training instead. That’s where the adaptations actually come from, and unlike your vitamin D level, it changes every single week.

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References

Footnotes

1. Ross AC, Manson JE, Abrams SA, Aloia JF, Brannon PM, Clinton SK, Durazo-Arvizu RA, Gallagher JC, Gallo RL, Jones G, Kovacs CS, Mayne ST, Rosen CJ, Shapses SA. “The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know.” Journal of Clinical Endocrinology & Metabolism, 2011;96(1):53-58. https://pubmed.ncbi.nlm.nih.gov/21118827/ ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹

2. Cui A, Xiao P, Ma Y, Fan Z, Zhou F, Zheng J, Zhang L. “Prevalence, trend, and predictor analyses of vitamin D deficiency in the US population, 2001-2018.” Frontiers in Nutrition, 2022;9:965376. https://pubmed.ncbi.nlm.nih.gov/36263304/ ↩ ↩² ↩³ ↩⁴

3. Farrokhyar F, Tabasinejad R, Dao D, Peterson D, Ayeni OR, Hadioonzadeh R, Bhandari M. “Prevalence of vitamin D inadequacy in athletes: a systematic-review and meta-analysis.” Sports Medicine, 2015;45(3):365-378. https://pubmed.ncbi.nlm.nih.gov/25277808/ ↩ ↩² ↩³ ↩⁴

4. Sist M, Zou L, Galloway SDR, Rodriguez-Sanchez N. “Effects of vitamin D supplementation on maximal strength and power in athletes: a systematic review and meta-analysis of randomized controlled trials.” Frontiers in Nutrition, 2023;10:1163313. https://pubmed.ncbi.nlm.nih.gov/37841405/ ↩ ↩² ↩³

5. LeBoff MS, Chou SH, Ratliff KA, Cook NR, Khurana B, Kim E, Cawthon PM, Bauer DC, Black D, Gallagher JC, Lee IM, Buring JE, Manson JE. “Supplemental Vitamin D and Incident Fractures in Midlife and Older Adults.” New England Journal of Medicine, 2022;387(4):299-309. https://pubmed.ncbi.nlm.nih.gov/35939577/ ↩ ↩² ↩³ ↩⁴ ↩⁵

6. Lappe J, Cullen D, Haynatzki G, Recker R, Ahlf R, Thompson K. “Calcium and vitamin D supplementation decreases incidence of stress fractures in female navy recruits.” Journal of Bone and Mineral Research, 2008;23(5):741-749. https://pubmed.ncbi.nlm.nih.gov/18433305/ ↩ ↩² ↩³

7. Burt LA, Billington EO, Rose MS, Raymond DA, Hanley DA, Boyd SK. “Effect of High-Dose Vitamin D Supplementation on Volumetric Bone Density and Bone Strength: A Randomized Clinical Trial.” JAMA, 2019;322(8):736-745. https://pubmed.ncbi.nlm.nih.gov/31454046/ ↩ ↩² ↩³ ↩⁴ ↩⁵

8. Demay MB, Pittas AG, Bikle DD, Diab DL, Kiely ME, Lazaretti-Castro M, Lips P, Mitchell DM, Murad MH, Powers S, Rao SD, Scragg R, Tayek JA, Valent AM, Walsh JME, McCartney CR. “Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline.” Journal of Clinical Endocrinology & Metabolism, 2024;109(8):1907-1947. https://pubmed.ncbi.nlm.nih.gov/38828931/ ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

9. Bârsan M, Chelaru VF, Râjnoveanu AG, Popa ȘL, Socaciu AI, Bădulescu AV. “Difference in Levels of Vitamin D between Indoor and Outdoor Athletes: A Systematic Review and Meta-Analysis.” International Journal of Molecular Sciences, 2023;24(8):7584. https://pubmed.ncbi.nlm.nih.gov/37108748/ ↩ ↩²

10. Farrokhyar F, Sivakumar G, Savage K, Koziarz A, Jamshidi S, Ayeni OR, Peterson D, Bhandari M. “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;47(11):2323-2339. https://pubmed.ncbi.nlm.nih.gov/28577257/ ↩ ↩² ↩³

11. Zhang L, Quan M, Cao ZB. “Effect of vitamin D supplementation on upper and lower limb muscle strength and muscle power in athletes: A meta-analysis.” PLoS One, 2019;14(4):e0215826. https://pubmed.ncbi.nlm.nih.gov/31039170/ ↩ ↩²

12. Chou SH, Cook NR, Kotler G, Kim E, Copeland T, Lee IM, Cawthon PM, Buring JE, Manson JE, LeBoff MS. “Effects of Supplemental Vitamin D3, Omega-3 Fatty Acids on Physical Performance Measures in the VITamin D and OmegA-3 TriaL.” Journal of Clinical Endocrinology & Metabolism, 2024;110(1):e44-e53. https://pubmed.ncbi.nlm.nih.gov/38488491/ ↩

13. Most A, Dörr O, Nef H, Hamm C, Bauer T, Bauer P. “Influence of 25-Hydroxy-Vitamin D Insufficiency on Maximal Aerobic Power in Elite Indoor Athletes: A Cross-Sectional Study.” Sports Medicine - Open, 2021;7(1):74. https://pubmed.ncbi.nlm.nih.gov/34648100/ ↩

14. Manson JE, Cook NR, Lee IM, Christen W, Bassuk SS, Mora S, Gibson H, Gordon D, Copeland T, D’Agostino D, Friedenberg G, Ridge C, Bubes V, Giovannucci EL, Willett WC, Buring JE. “Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease.” New England Journal of Medicine, 2019;380(1):33-44. https://pubmed.ncbi.nlm.nih.gov/30415629/ ↩

15. Jolliffe DA, Camargo CA Jr, Sluyter JD, Aglipay M, Aloia JF, Bergman P, Bischoff-Ferrari HA, Borzutzky A, Bubes VY, Damsgaard CT, Ducharme FM, Dubnov-Raz G, Esposito S, Ganmaa D, Gilham C, Ginde AA, Golan-Tripto I, Goodall EC, Grant CC, Griffiths CJ, Hibbs AM, Janssens W, Khadilkar AV, Laaksi I, Lee MT, Loeb M, Maguire JL, Majak P, Manaseki-Holland S, Manson JE, Mauger DT, Murdoch DR, Nakashima A, Neale RE, Pham H, Rake C, Rees JR, Rosendahl J, Scragg R, Shah D, Shimizu Y, Simpson-Yap S, Kumar GT, Urashima M, Martineau AR. “Vitamin D supplementation to prevent acute respiratory infections: systematic review and meta-analysis of stratified aggregate data.” Lancet Diabetes & Endocrinology, 2025;13(4):307-320. https://pubmed.ncbi.nlm.nih.gov/39993397/ ↩ ↩² ↩³

16. Sanders KM, Stuart AL, Williamson EJ, Simpson JA, Kotowicz MA, Young D, Nicholson GC. “Annual high-dose oral vitamin D and falls and fractures in older women: a randomized controlled trial.” JAMA, 2010;303(18):1815-1822. https://pubmed.ncbi.nlm.nih.gov/20460620/ ↩ ↩²

17. Fabregat-Bolufer AB, Martín-Alonso C, Escolà-Rodríguez A, Morales-Ruiz M. “Overdiagnosed and oversupplemented: the iatrogenic rise of vitamin D toxicity.” European Journal of Endocrinology, 2026;194(6):K21-K25. https://pubmed.ncbi.nlm.nih.gov/42145024/ ↩ ↩² ↩³ ↩⁴