Some may not meet the threshold even after supplementing with daily 2000 IUs of vitamin D, like patients with inflammatory bowel disease during episodes of high disease activity. Even medications, like antiepileptic drugs, can affect lower serum 25(OH)D concentrations by modulating its metabolism.
When serum 25(OH)D concentrations exceed 150 ng/mL, vitamin D toxicity may lead to hypercalcemia; thus, clinicians advise caution for those on vitamin D supplements. Recent RCTs like the Vitamin D and OmegA-3 Trial (VITAL) gathered safety data on using 2000 IU of vitamin D/day in general adult populations who showed no signs of vitamin D toxicity for 5.3 years, indicating the safety of this daily dosage.
Further, a meta-analysis of 15 vitamin D RCTs found no increase in kidney stones when supplementing with ≥70 µg of vitamin D for at least one year. Another meta-analysis found that daily vitamin D supplementation of 3200-4000 IUs for six months increased the risk of hypercalcemia, hospitalizations, and falls; however, this did not occur in chronic kidney disease patients.
Adherence to conservative dosing regimens not exceeding 800 IU (20 µg) of vitamin D per day may not sufficiently treat vitamin D deficiency, considering the heterogeneity in inter-individual dose-response and accounting for the multiple clinical factors involved, such as obesity, malabsorption syndromes, and medications that impair vitamin D metabolism.
This review revealed that daily vitamin D supplementation was more effective than intermittent bolus dosing in adults. However, precaution is needed for older and diseased individuals, who are more prone to adverse effects of vitamin D overdosing.
In real-world settings, clinicians should consider tailoring the vitamin D dosage according to the patient's needs and characteristics. Instead of following the 'one-size fits all' approach, they may adopt a personalized treatment approach and prescribe a dosing range from 800-2000 IUs (20-50 µg).
It is a narrative review lacking a pre-registered systematic review. Yet, based on the evidence outlined in this review, the authors argue in favor of a daily vitamin D supplement dose of 2000 IU (50 µg) to raise and maintain serum 25(OH)D concentrations >50 nmol/L (20 ng/mL) and >75 nmol/L (30 ng/mL) in >99% and >90% of the general adult population, respectively.
Furthermore, they found no significant safety concerns in supplementing such a dose for several years, even in individuals with a sufficient vitamin D status at baseline. This could be the perfect remedy for addressing the vitamin D pandemic in the general adult population.
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