title: An update on vitamin D for clinicians.
abstract: OBJECTIVE
  The clinical benefits of vitamin D therapy have received substantial attention over the past decade. Recently, several trials looked to clarify the optimal vitamin D dose or serum level needed to promote human health. The purpose of this review is to highlight selected studies published since January 2015.
  
  
  RESULTS
  Several recent trials challenge whether serum vitamin D levels at least 30 ng/ml promote human health. In postmenopausal women with 25-hydroxyvitamin D [25(OH)D] levels 21 ± 3 ng/ml, high-dose vitamin D for 1 year increased calcium absorption by 1%, without changes in bone mineral density, physical function, or falls when compared with low-dose vitamin D and placebo. High-dose vitamin D increased risk of falling in 200 adults 78 ± 5 years old with baseline 25(OH)D levels of ∼19 ± 9 ng/ml. High-dose vitamin D in adults increased the number and duration of upper respiratory tract infections compared with placebo. Asthma patients achieving 25(OH)D levels more than 30 ng/ml during a trial experienced more respiratory infections than those not achieving such levels.
  
  
  CONCLUSIONS
  Recent studies are congruent with the Institute of Medicine's conclusion that humans are vitamin D replete when their serum 25(OH)D levels are at least 20 ng/ml. Higher levels seem to promote falls and respiratory infections.
authors.affiliation: Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Karen E
authors.initials: KE
authors.lastname: Hansen
authors.forename: Michael G
authors.initials: MG
authors.lastname: Johnson
mesh_terms: D000058:Accidental Falls / Q000706:statistics & numerical data; D000368:Aged; D000369:Aged, 80 and over; D001249:Asthma; D015519:Bone Density; D002136:Calcium, Dietary / Q000493:pharmacokinetics / Q000627:therapeutic use; D005260:Female; D006293:Health Promotion; D006801:Humans; D017698:Postmenopause; D012141:Respiratory Tract Infections / Q000453:epidemiology; D014807:Vitamin D / Q000008:administration & dosage* / Q000009:adverse effects / Q000031:analogs & derivatives / Q000097:blood; D014808:Vitamin D Deficiency / Q000188:drug therapy
chemical_list: D002136:Calcium, Dietary; D014807:Vitamin D; C104450:25-hydroxyvitamin D