Elsevier

The Lancet

Volume 358, Issue 9292, 3 November 2001, Pages 1500-1503
The Lancet

Articles
Intake of vitamin D and risk of type 1 diabetes: a birth-cohort study

https://doi.org/10.1016/S0140-6736(01)06580-1Get rights and content

Summary

Background

Dietary vitamin D supplementation is associated with reduced risk of type 1 diabetes in animals. Our aim was to ascertain whether or not vitamin D supplementation or deficiency in infancy could affect development of type 1 diabetes.

Methods

A birth-cohort study was done, in which all pregnant women (n=12 055) in Oulu and Lapland, northern Finland, who were due to give birth in 1966 were enrolled. Data was collected in the first year of life about frequency and dose of vitamin D supplementation and presence of suspected rickets. Our primary outcome measure was diagnosis of type 1 diabetes by end of December, 1997.

Findings

12 058 of 12 231 represented live births, and 10 821 (91% of those alive) children were followed-up at age 1 year. Of the 10 366 children included in analyses, 81 were diagnosed with diabetes during the study. Vitamin D supplementation was associated with a decreased frequency of type 1 diabetes when adjusted for neonatal, anthropometric, and social characteristics (rate ratio [RR] for regular vs no supplementation 0·12, 95% Cl 0·03–0·51, and irregular vs no supplementation 0·16, 0·04–0·74. Children who regularly took the recommended dose of vitamin D (2000 IU daily) had a RR of 0·22 (0·05–0·89) compared with those who regularly received less than the recommended amount. Children suspected of having rickets during the first year of life had a RR of 3·0 (1·0–9·0) compared with those without such a suspicion.

Interpretation

Dietary vitamin D supplementation is associated with reduced risk of type 1 diabetes. Ensuring adequate vitamin D supplementation for infants could help to reverse the increasing trend in the incidence of type 1 diabetes.

Introduction

Exactly what causes the destruction of insulin secreting β cells in the pancreas, and thus the development of type 1 diabetes, remains unknown, though cytokines, T cells, and macrophages have all been implicated.1 In vitro, vitamin D acts as an immunosuppressive agent, reducing lymphocyte proliferation and cytokine production.2 Furthermore, in animals, the administration of vitamin D (1,25 (OH)2D3) seems to prevent development of type 1 diabetes.3, 4

Factors in infancy can affect the risk of development of diabetes in later life. The results of a large case-control study suggest that vitamin D supplementation during early childhood can prevent type 1 diabetes.5 Another study also found an inverse relation between maternal use of cod liver oil during pregnancy and the frequency of type 1 diabetes in their children.6 Our aim was to ascertain whether or not dietary supplementation with vitamin D in infancy could reduce the risk of type 1 diabetes.

Section snippets

Participants

All women (n=12 055) living in Oulu and Lapland, northern Finland, whose pregnancy continued after the 24th week of gestation, and for whom the estimated date of delivery fell during 1966 were enrolled.7 Between the 24th and 28th week of gestation, the women were asked to fill in a questionnaire to obtain background information. A questionnaire about the birth and the status of the neonate was filled in by the attending midwife.7 12 058 children were born alive out of 12 231 births. 10 821 (91%

Results

9124 (88·0%) children were given vitamin D supplements regularly, and 1210 (11·7%) irregularly. 32 (0·3%) infants were not given vitamin D. Of those who received vitamin D regularly, 8582 (94%) had the recommended daily amount, and 434 (5%) and 71 (1%) received more or less than the recommended amount, respectively. In the first year of life, 216 (2%) children who took vitamin D had suspected rickets (table 1). Of these, dietary supplementation was irregular in 56 (26%), and 132 (61%) had

Discussion

Our results suggest that development of type 1 diabetes is associated with low intake of vitamin D and signs of rickets during the first year of life. In view of the fact that vitamin D acts as an immunosuppressive agent,2, 12 and that type 1 diabetes is believed to be an autoimmune disease,1 these findings are not surprising. To be classified as an autoimmune disease, the progress of the disorder must be slowed down or prevented by immunosuppressive therapy.13 We believe that vitamin D might

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