Table 4.

The effect of vitamin D supplementation after surgery-induced weight loss on vitamin D status

Authors (year)	Study population	Intervention	Study design	Measurements	Average 25(OH)D change
				Weight	25(OH)D	PTH
RCT
Carlin et al (2009) [66]	n=60 obese women with pre-surgery vitD depletion	12 months Roux-en-Y gastric bypass 50,000 UI vitD/day No additional vitD	RCT	✓	✓	✓	Intervention: 16.32 ± 15.7 Control: −4.44 ± 11.4
Goldner et al (2009) [88]	n=45 obese women (n=36) or men (n=9) (>19y)	24 months Roux-en-Y gastric bypass 800 UI vitD 2,000 UI vitD 5,000 UI vitD post-surgery supplementation/day	RCT	✓	✓	✓	800 IU: +27.7 ± 40.0 nmol/L 2,000 IU 60.2 ± 37.4 nmol/L 5,000 IU 66.1 ± 42.2 nmol/L
Intervention study
Flores et al (2015) [86]	Study 1: n=176 obese women (n=140) or men (n=36) Study 2: n= 52 obese women (n=32) or men (n=20)	12 months bariatric surgery 1,000mg Ca citrate/day and 800 IU vitD/d Study1: pre-op vitD supplementation according to vitD level Study2: additional high dose of 2,000 IU vitD/day	Intervention Study	✓	✓	✓	Study 1: level increased from 40 to 77 nmol/L (p<0.001) no difference between different doses Study 2: level increased from 32 to 75 nmol/L (p, 0.001)
Lanzarini et al (2015) [89]	n=164 obese women (n=124) or men (n=40) (18–60y)	24 months bariatric surgery 400 IU vitD/day Intervention (n=106): additional supplementation with 16,000 IU vitD every 2 weeks if 25(OH)D serum levels were <30ng/ml	Intervention study	✓	✓	✓	Normal levels after 24 months: Intervention group: 68% of the patients Non-Intervention: 48.8% of the patients
Flores et al (2010) [87]	n=222 women (n=163) or men (n=59) (18–65y)	12 months gastric bypass patients with PTH >70 pg/ml received 1,200 mg/d Ca and 800 IU vitD/d	Intervention study	✓	✓	✓	with supplementation increase of only 11.5 nmol/L

Abbreviations: 25(OH)D, 25-hydroxyvitamin D; PTH, parathyroid hormone; vitD, vitamin D; IU vitD, International Unit vitamin D (=0,025 μg vitD); RCT, randomized controlled trial; y, year