Vitamin D Boost in Infancy May Prevent Type 1 Diabetes
MANCHESTER, England, March 13 -- Vitamin D supplements early in life may help ward off type 1 diabetes, according to a meta-analysis.
given extra vitamin D were 29% less likely to develop type 1 diabetes
than those not given the supplement, found Christos Zipitis, MBChB, of
St. Mary's Hospital for Women and Children here, and Anthony K.
Akobeng, M.D., M.P.H., of the Central Manchester and Manchester
Children's University Hospitals.
Higher doses appeared to be more effective, they reported online in the Archives of Disease in Childhood.
D plays a physiological role in the immune system, and evidence also
suggests it protects against cytokine-induced dysfunction of pancreatic
beta cells, they wrote. But vitamin D levels and supplement dosages
have declined over the last few decades.
in the summer and at lower latitudes, many infants are so thoroughly
protected from sun exposure that they produce little endogenous vitamin
D," they wrote.
population vitamin D levels have led to a resurgence of rickets and
hypocalcemia as well as speculation that vitamin D may be contributing
to increasing incidence of autoimmune conditions including type 1
diabetes, the researchers said.
meta-analysis included four case-control studies and one cohort study
on the association between vitamin D supplementation in infancy and
subsequent development of type 1 diabetes.
studies were done in healthy children followed up to ages 15 or 30.
None objectively measured vitamin D status, reported total vitamin D
intake from diet or sun exposure, or compared ethnic backgrounds in
cases and controls. The cohort study likewise did not objectively
measure vitamin D status and was not blinded.
the three case-control studies with sufficient data for meta-analysis,
the 1,429 children given vitamin D supplements were 29% less likely to
develop type 1 diabetes than the 5,026 participants who were not given
supplements (OR 0.71, 95% CI 0.60 to 0.84).
cohort study likewise found that regular vitamin D supplementation
reduced the relative risk of type 1 diabetes significantly (RR 0.12,
95% CI 0.03 to 0.51) as did even irregular use (RR 0.16, 95% CI 0.04 to
Higher cumulative doses of vitamin D appeared to increase the benefit of supplementation.
one study, 10 mg of vitamin D supplements in the form of cod liver oil
given one to four times per week reduced type 1 diabetes risk 19% (OR
0.81, 95% CI 0.55 to 1.19) while five or more times a week dosing
reduced risk 26% (OR 0.74, 95% CI 0.56 to 0.99).
another study, regular use of the recommended 2,000 IU vitamin D dose
reduced risk compared with regular use of a lower dose (RR 0.22, 95% CI
0.05 to 0.89).
longer duration of vitamin D supplementation, though, did not appear to
substantially improve risk in the one study that looked at this factor
(OR 0.69 for less than a year versus 0.64 for more than a year).
early supplementation didn't appear to be any better than starting
later in infancy in the one study that looked at age at initiation. Cod
liver oil supplements from age seven to 12 months were actually
associated with lower likelihood of developing type 1 diabetes in later
life compared with supplements from zero to six months of age (OR 0.55
may simply reflect longer duration of supplementation, but feeding and
other unmeasured variables could also be responsible, the researchers
researchers noted that the findings were limited by the overall
moderate quality of the studies included, which may have been subject
to recall bias, did not include objective vitamin D measures, and may
not have controlled for all potential confounding factors.
Despite these limitations, Drs. Zipitis and Akobeng said that criteria for causality seemed to be fulfilled.
"However, for concrete conclusions to be reached," they cautioned, "adequately powered, randomized controlled trials with long periods of follow-up would be required to establish causality and the best formulation, dose, duration, and period of supplementation."
Primary source: Archives of Disease in Childhood
Zipitis CS, Akobeng AK "Vitamin D supplementation in early childhood and risk of type 1 diabetes: A systematic review and meta-analysis"Arch Dis Child 2008; DOI: 10.1136/adc.2007.128579.
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