Table 3: Vitamin D supplementation and risk of T1DM development.

Study design (year)
Country PopulationVitamin D supplements DurationResults (relative risk of T1D with vitamin D supplements)

EURODIAB (no authors listed)
Case control study (1999) [96]
7 countries in Europe746 T1DM and 2188 controls Vitamin D supplementation during infancy31 years 0.67 (0.53, 0.86)
Stene et al.
Case control study (2000) [98]
Norway78 T1DM and 980 controls Cod liver oil to pregnant women 16 years 0.36 (0.14–0.9)
Hyppönen et al.
Birth control, prospective study (2001) [97]
Finland81 T1DM and 10366 controls Cod liver oil to children during the first year of life (2000IU daily)31 years 0.22 (0.05–0.89) for regular or irregular vitamin D intake versus no supplements
0.12 (0.03–0.51) for regular vitamin D supplements versus no supplements
Fronczak et al.
Cohort study (2003) [100]
Colorado 16 T1DM and 206 controls Vitamin D supplementation in food, during the third trimester of pregnancy (250IU daily)4 years 0.37 (0.17–0.78)
Stene and Joner   
Case control study (2003) [99]
Norway545 T1DM and 1668 controls Cod liver oil in the first year of life, at 7–12 months of age (10 mcg daily for at least 5 times per week)15 years 0.74 (0.56–0.99)
Tenconi et al.
Case control study (2007) [101]
North Italy159 T1DM and 318 controls Vitamin D supplementation during lactation 29 years 0.33 (0.14–0.81)
Brekke et al.
Cohort retrospective and prospective study (2007) [102]
Sweden8.7% at 1 year and 8.9% at 2.5 years had positive antibodies Vitamin D supplementation during pregnancy (10 mcg daily)2.5 years 0.71 (0.17–0.78)
Marjamäki et al.
Birth cohort study (2010) [103]
Finland165 patients with positive antibodies and 4297 controlVitamin D supplements during pregnancy (mean supplements 5.1 mcg and 1.3 mcg in food, daily) 4 years No significant protective effect