Question explored with the scientific record
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- 1 Is it worth taking vitamin d supplements
- 2 What kind of vitamin d supplement and what dosage is likely to be most helpful
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What kind of vitamin d supplement and what dosage is likely to be most helpful
The short version: take D3, not D2, and dose to your blood level, not to a label.
Vitamin D3 beats D2 at raising blood levels. A meta-analysis of 10 trials found D3 more effective [2], and a direct comparison in women over 65 showed 800 IU of D3 lifted levels from 14 to 22.9 ng/ml while the same dose of D2 only reached 16.3 [6]. D2 is the cheaper, plant-derived form; skip it unless that is all you have.
On dose, the honest answer is that it depends on your starting level, your body fat, and your age. In premenopausal women, 20 mcg (800 IU) daily through winter got about 80 in 100 to the target of 75 nmol/L [5]. In UK adolescents, 20 mcg daily beat 10 mcg [3]. Obese children responded far worse than lean children to the same D3 dose [1]. Older adults generally need more than younger ones to reach the same level [9]. A single 300,000 IU dose did raise severely deficient elderly patients to target at three months [4], but that is a correction dose, not maintenance.
| Situation | Reasonable daily D3 | Basis |
|---|---|---|
| Healthy adult, maintenance | 800 to 2,000 IU | [5][3] |
| Known deficiency | Higher, then retest | [4][9] |
| Obese | Expect a weaker response | [1] |
| Older adult | Often needs more | [9] |
The dose ceiling matters. A 3-year trial found hypercalciuria in 23 in 100 adults on 400 to 10,000 IU, worse at the high end [8]. One infant got severe toxicity from an over-the-counter product that contained three times its label [7]. Test your level, dose to it, and retest.
My call: D3, 800 to 2,000 IU daily for most adults, adjusted to a measured blood level. Confidence: moderate on the form, low on the exact dose for any individual.
Sources used 9
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Assessment of Vitamin D Status and Response to Vitamin D3 in Obese and Non-Obese Iranian Children
This study investigates the serum 25-hydroxyvitamin D status and therapeutic response to vitamin D3 supplementation in obese versus non-obese Iranian children, revealing a significantly higher prevalence of vitamin D deficiency in obese children and a lower therapeutic response …
DOI: 10.1093/tropej/fmv091 -
Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis
This systematic review and meta-analysis found that vitamin D3 supplementation is significantly more effective than vitamin D2 in raising serum 25-hydroxyvitamin D concentrations in humans.
DOI: 10.3945/ajcn.111.031070 -
Effect of vitamin D 3 supplementation on serum 25-hydroxyvitamin D status among adolescents aged 14–18 years: a dose-response, randomised placebo-controlled trial
This study investigates the effects of different doses of vitamin D3 supplementation on serum 25-hydroxyvitamin D concentrations in UK adolescents during winter, finding that both 10 µg and 20 µg doses maintain adequate vitamin D levels, with the higher dose being more effective.
DOI: 10.1017/S0029665116001324 -
High-dose oral vitamin D3 supplementation in rheumatology patients with severe vitamin D3 deficiency
This study demonstrates that a single oral dose of 300,000 IU of vitamin D3 significantly increases serum 25-hydroxyvitamin D levels in elderly patients with severe vitamin D deficiency, achieving target levels for most patients at three months post-treatment.
DOI: 10.1016/j.bone.2009.06.012 -
Supplements of 20 μg/d Cholecalciferol Optimized Serum 25-Hydroxyvitamin D Concentrations in 80% of Premenopausal Women in Winter
A randomized, double-blind trial in Premenopausal women in Maine found that daily 20 mg of cholecalciferol (D3) during fall/winter raised serum 25-hydroxyvitamin D [25(OH)D] to optimal levels (≥75 nmol/L) in about 80% of participants, with baseline vitamin D status, body fat, an…
DOI: 10.3945/jn.108.096180 -
Vitamin D2 or vitamin D3 supplementation in daily dose: Are they equivalent?
This study compares the efficacy of daily doses of vitamin D2 and D3 in increasing serum 25-hydroxyvitamin D levels in healthy women over 65 years, finding that D3 is more effective than D2.
DOI: 10.1016/j.bone.2011.03.745 -
Iatrogenic vitamin D toxicity in an infant – a case report and review of literature
This case report details a 4-month-old infant who developed severe hypercalcemia and nephrocalcinosis due to iatrogenic vitamin D toxicity from an over-the-counter supplement that contained three times the labeled dose, highlighting the risks associated with unregulated vitamin …
DOI: 10.1016/j.jsbmb.2015.01.022 -
The complex relationship between vitamin D and kidney stones: balance, risks, and prevention strategies
Vitamin D deficiency and excess may both raise kidney stone risk via calcium–phosphorus metabolism, yet trial evidence on supplementation is contradictory and moderate doses under 4,000 IU/day appear generally safe.
DOI: 10.3389/fnut.2024.1435403 -
Correcting poor vitamin D status: Do older adults need higher repletion doses of vitamin D 3 than younger adults?
Reviewing vitamin D3 repletion studies, the authors concluded older adults generally require higher supplementary doses than younger adults to reach 25(OH)D of 75 nmol/L, with daily doses above 2000 IU in younger and 5000 IU in older adults.
DOI: 10.1002/mnfr.200900536