The DALI vitamin D randomized controlled trial for gestational diabetes mellitus prevention: No major benefit shown besides vitamin D sufficiency

Rosa Corcoy, Lilian C Mendoza, David Simmons, Gernot Desoye, J M Adelantado, Ana Chico, Roland Devlieger, Andre van Assche, Sander Galjaard, Dirk Timmerman, Annunziata Lapolla, Maria G Dalfra, Alessandra Bertolotto, Jürgen Harreiter, Ewa Wender-Ozegowska, Agnieszka Zawiejska, Alexandra Kautzky-Willer, Fidelma P Dunne, Peter Damm, Elisabeth R MathiesenDorte M Jensen, Lise Lotte T Andersen, Mette Tanvig, David J Hill, Judith G Jelsma, Frank J Snoek, Harald Köfeler, Martin Trötzmüller, Paul Lips, Mireille N M van Poppel

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BACKGROUND & AIMS: As vitamin D deficiency is associated with an increased risk of gestational diabetes mellitus (GDM), we aimed to test vitamin D supplementation as a strategy to reduce GDM risk (evaluated after fasting plasma glucose (FPG), insulin resistance and weight gain) in pregnant overweight/obese women.

METHODS: The DALI vitamin D multicenter study enrolled women with prepregnancy body mass index (BMI) ≥ 29 kg/m2, ≤19 + 6 weeks of gestation and without GDM. Participants were randomized to receive 1600 IU/day vitamin D3 or placebo (each with or without lifestyle intervention) on top of (multi)vitamins supplements. Women were assessed for vitamin D status (sufficiency defined as serum 25-hydroxyvitamin D (25(OH)D) ≥ 50 nmol/l), FPG, insulin resistance and weight at baseline, 24-28 and 35-37 weeks. Linear or logistic regression analyses were performed to assess intervention effects.

RESULTS: Average baseline serum 25(OH)D was ≥50 nmol/l across all study sites. In the vitamin D intervention arm (n = 79), 97% of participants achieved target serum vitamin 25(OH)D (≥50 nmol/l) at 24-28 weeks and 98% at 35-37 weeks vs 74% and 78% respectively in the placebo arm (n = 75, p < 0.001). A small but significantly lower FPG (-0.14 mmol/l; CI95 -0.28, -0.00) was observed at 35-37 weeks with the vitamin D intervention without any additional difference in metabolic status, perinatal outcomes or adverse event rates.

CONCLUSION: In the DALI vitamin D trial, supplementation with 1600 IU vitamin D3/day achieved vitamin D sufficiency in virtually all pregnant women and a small effect in FPG at 35-37 weeks. The potential of vitamin D supplementation for GDM prevention in vitamin D sufficient populations appears to be limited.


Original languageEnglish
JournalClinical Nutrition
Issue number3
Pages (from-to)976-984
Publication statusPublished - Mar 2020


  • Fasting plasma glucose
  • Fasting plasma insulin
  • Gestational diabetes mellitus
  • Pregnancy
  • Vitamin D sufficiency
  • Vitamin D supplementation


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