How long does vitamin d take to work
Pro Research Analysisby 
Searched over 200M research papers
How Long Does Vitamin D Take to Work?
Vitamin D Absorption and Initial Effects
Vitamin D, whether obtained through sunlight exposure, diet, or supplements, undergoes a series of transformations before it becomes active in the body. The initial conversion of vitamin D in the skin to its active form can take at least three days to complete 7. Once converted, vitamin D3 is slowly released into the circulation, ensuring a steady supply.
Short-Term Biological Activity
The immediate biological effects of vitamin D can be observed within hours to days. For instance, a vitamin D metabolite has been shown to stimulate intestinal calcium transport within 8-10 hours after administration in vitamin D-deficient rats, whereas vitamin D itself required about 20 hours to show similar effects 3. This indicates that some of the physiological actions of vitamin D can begin relatively quickly after intake.
Medium-Term Effects on Health Conditions
In clinical settings, the effects of vitamin D supplementation on specific health conditions can be observed over several weeks to months. For example, a study on Crohn's disease patients demonstrated that seven weeks of high-dose vitamin D treatment significantly reduced the need for infliximab dose escalation and decreased inflammatory markers over a one-year follow-up period 4. This suggests that while some benefits can be seen within weeks, the full therapeutic effects may take longer to manifest.
Long-Term Benefits and Longevity
Long-term benefits of vitamin D supplementation can extend well beyond the period of active intake. A study on postmenopausal women found that the benefits of daily vitamin D3 supplementation persisted for up to two years after cessation, with a lower proportion of vitamin D-deficient women compared to those who took a placebo 5. This indicates that vitamin D can have lasting effects on the body's vitamin D status.
Cognitive Function Improvement
In older adults with mild cognitive impairment, a 12-month vitamin D supplementation regimen showed significant improvements in cognitive function, suggesting that sustained intake over a year is necessary to observe substantial cognitive benefits 2. This highlights the importance of long-term supplementation for certain health outcomes.
Conclusion
The time it takes for vitamin D to work can vary depending on the specific health outcome being measured. Initial physiological effects can be observed within hours to days, while improvements in certain health conditions may take weeks to months. Long-term benefits, particularly in maintaining adequate vitamin D levels, can persist for years after supplementation has ceased. Therefore, consistent and prolonged intake of vitamin D is crucial for achieving and maintaining its full range of health benefits.
Sources and full results
Most relevant research papers on this topic
Vitamin D Supplementation Improves Cognitive Function Through Reducing Oxidative Stress Regulated by Telomere Length in Older Adults with Mild Cognitive Impairment: A 12-Month Randomized Controlled Trial
Vitamin D supplementation for 12 months improves cognitive function in older adults with mild cognitive impairment by reducing oxidative stress regulated by telomere length.
RCT
Rigorous JournalBiological activity of a vitamin D metabolite
A vitamin D metabolite, found in rat carcasses, effectively cures rickets, stimulates intestinal calcium transport, and increases serum calcium levels, with a shorter lag time compared to vitamin D.
Highly CitedSeven Weeks of High-Dose Vitamin D Treatment Reduces the Need for Infliximab Dose-Escalation and Decreases Inflammatory Markers in Crohn’s Disease during One-Year Follow-Up
High-dose vitamin D treatment for seven weeks reduces the need for infliximab dose-escalation and decreases inflammatory markers in Crohn's disease patients during one-year follow-up.
RCT
Very Rigorous JournalLongevity of daily oral vitamin D3 supplementation: differences in 25OHD and 24,25(OH)2D observed 2 years after cessation of a 1-year randomised controlled trial (VICtORy RECALL)
Daily vitamin D3 supplementation shows benefits over placebo 2 years after discontinuing treatment, with vitamin D-binding protein being a predictor of vitamin D longevity.
RCTRigorous JournalBioavailability of vitamin D(2) and D(3) in healthy volunteers, a randomized placebo-controlled trial.
Vitamin D3 increases total 25(OH)D concentration more than vitamin D2, while vitamin D2 supplementation leads to a decrease in 25(OH)D3, explaining the different effect on total 25(OH)D.
RCTRigorous JournalHighly CitedPhotosynthesis of previtamin D3 in human skin and the physiologic consequences.
Photosynthesis of previtamin D3 in human skin occurs when exposed to solar ultraviolet radiation, and its slow, steady release into the circulation is a unique mechanism for vitamin D3 synthesis, storage, and release.
Highly CitedEvaluation of a 12-week targeted vitamin D supplementation regimen in patients with active inflammatory bowel disease.
A 12-week targeted vitamin D supplementation regimen successfully achieved target levels and improved symptom-based activity scores in patients with active inflammatory bowel disease, but did not alter objective measures of intestinal or systemic inflammation.
Non-RCTVery Rigorous JournalMonthly Increase in Vitamin D Levels upon Supplementation with 2000 IU/Day in Healthy Volunteers: Result from “Integriamoci”, a Pilot Pharmacokinetic Study
Vitamin D levels can increase rapidly after daily supplementation with 2000 IU/day, reducing deficiency in 62% of healthy volunteers after 28 days.
Non-RCTThe effect of vitamin D supplementation on glycemic status of elderly people with prediabetes: a 12-month open-label, randomized-controlled study
Vitamin D supplementation can improve glycemic status in elderly people with prediabetes, potentially complementing lifestyle changes in managing this condition.
RCT