Higher blood 25 (OH) D is associated with lower risk of type 2 diabetes (T2D) in people with prediabetes. Blood 25 (OH) D can vary due to skin color and weight. It is not known if blood 25 (OH) D levels have similar impact on T2D risk for people of color or higher weight.

The vitamin D and type 2 diabetes (D2d) study is a randomized clinical trial of participants with high-risk prediabetes and overweight/obesity who were randomized to vitamin D3 4000 IU daily vs. placebo and followed for 2.5 years for the primary outcome of T2D. We compared baseline and intra-trial (mean achieved) serum 25 (OH) D among race-weight groups. We used Cox models to determine the associations between intra-trial serum 25 (OH) D and T2D risk by race-weight groups; we additionally tested for interactions between intra-trial serum 25 (OH) D and race or weight.

Of 2362 D2d participants with self-reported race, Black (n = 616) and White (n = 1616) participants were included in analyses. Baseline serum 25 (OH) D was lower in Black (24.2 ng/mL ± 10.9) compared to White (29.6 ng/mL ± 9.5) participants (P<0.001) ; and were lower in those with higher vs. lower BMI in both races. Intra-trial serum 25 (OH) D was lower in Black participants (P<0.001) overall and those with higher baseline BMI. Both Black and White participants with intra-trial serum 25 (OH) D ≥ 40 ng/mL had significantly reduced risk of T2D [HR (95% CI) ]; Black: 0.51 (0.29, 0.92) ; White 0.42 (0.30, 0.60) ] with no significant race*BMI interaction. Participants with baseline BMI ≤ 40 kg/m2 who achieved intra-trial serum 25 (OH) D levels ≥ 40 ng/mL had significantly reduced risks of T2D but not those with a BMI > 40 kg/m2 with no significant BMI*race interaction.

Conclusions: An intra-trial mean serum 25 (OH) D level ≥ 40 ng/mL was associated with significantly reduced risk of T2D in Black and White D2d participants, but only among those with BMI < 40 kg/m2. Targeting a serum 25 (OH) D level ≥ 40 ng/mL would optimize T2D prevention efforts among people with high-risk prediabetes.


R.Chatterjee montgomery: Research Support; Bristol-Myers Squibb Company, Epigenomics AG. B.Dawson-hughes: None. D2d research group: n/a. C.A.Davenport: None. K.C.Johnson: None. S.Kashyap: Advisory Panel; Fractyl Health, Inc., GI Dynamics, Research Support; Janssen Pharmaceuticals, Inc. E.S.Leblanc: n/a. J.P.Nelson: None. E.Vickery: None. S.Dagogo-jack: Consultant; AstraZeneca, Bayer AG, Boehringer Ingelheim International GmbH, Janssen Pharmaceuticals, Inc., Medtronic, Merck & Co., Inc., Sanofi. A.G.Pittas: None.


American Diabetes Association (1-14-D2d-01) ; National Institutes of Health National Institute of Diabetes and Digestive and Kidney Diseases and Office of Dietary Supplements (U01DK098245)

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