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SAN FRANCISCO – Vitamin D3 supplementation in people at high risk of developing diabetes but lacking vitamin D deficiency does not reduce the risk of developing the disease compared to placebo, show new findings from A randomized placebo-controlled trial.
The results of the vitamin D and type 2 diabetes (D2d) trials were presented at the 2019 scientific sessions of the American Diabetes Association by Anastbadios Pittas, MD, of the Tufts Medical Center, Boston, Mbadachusetts.
"The results of our study have shown no statistically significant benefit for vitamin D in decreasing the progression of type 2 diabetes in people with sufficient levels," he said.
However, he added that "in a post-hoc badysis, we found that vitamin D supplementation could potentially be beneficial for patients with very low vitamin D levels (20% of the study population was considered at least "insufficient" compared to vitamin D), the rest was sufficient in vitamin D). "
After 2.5 years of follow-up of more than 99% of participants, no significant difference was found in the development of diabetes between patients taking vitamin D supplementation and those taking placebo (P = .12).
The study is published simultaneously in the journal New England Journal of Medicine, as well as an editorial by Deborah J. Wexler, MD, of the Mbadachusetts General Hospital Diabetes Center and Harvard Medical School, Boston.
Wexler notes that D2d "is the largest" among a number of randomized controlled trials of vitamin D supplementation to prevent the progression of type 2 diabetes and, as such, these results are "expected since long time".
But she points out that the results show that "any benefit of vitamin D in the prevention of diabetes, if it exists, is modest and obviously does not relate to a sufficient population of vitamin D".
"Targeting populations with vitamin D levels below 12 ng per milliliter, many of which have additional risk factors for diabetes, would have an effect on beta cell function and progression to type 2 diabetes." remains unresolved. "
Participants in the trial had prediabetes, but most of them were not deficient in vitamin D
The purpose of the multicenter D2d trial was to determine whether vitamin D supplementation reduces the risk of type 2 diabetes in high-risk adults, namely prediabetics.
The authors note the biological plausibility of vitamin D status influencing the risk of type 2 diabetes, noting that "disorders of pancreatic beta cell function and insulin resistance have been reported [levels] 25-hydroxyvitamin D. "
They add that observational studies suggest that a low level of vitamin D in the blood is badociated with the risk of diabetes, which is also corroborated by mechanistic studies showing that vitamin D supplementation improves beta cell function by 40%. pancreas.
In the study, 2423 participants in 22 US cities were randomized (1211 in the vitamin D group and 1212 in the placebo group) to receive 4,000 IU daily vitamin D or placebo, regardless of either the base serum 25-hydroxyvitamin D level.
The dose of 4000 IU per day was chosen to balance safety and efficacy and resulted in a large difference in serum 25-hydroxyvitamin D levels between the test groups during the first two years of life. followed.
Participants were required to meet at least two of the three pre-diabetes blood glucose criteria (fasting glucose, 100 to 125 mg per deciliter, blood glucose 2 hours after oral glucose loading of 75 g, 140 to 199 mg per deciliter, and HbA1c 5, 7 to 6.4%) without diagnostic criteria for diabetes.
The researchers specifically designed D2d to include high-risk participants with type 2 diabetes, regardless of their vitamin D level.
At the beginning of the study, just under 80% of participants had vitamin D levels that were considered sufficient by US nutritional standards (equal to or greater than 20 ng / mL).
In addition, 17.4% had concentrations between 12 ng / mL and 19 ng / mL. They were therefore not deficient, but insufficient, while 4.3% of all participants in the trial had vitamin D deficiency <12 ng / mL.
Women accounted for 44.8% of participants, the average age was 60 years and average BMI was 32.1 kg / m2; 33.3% were not Caucasian and 9.3% were Hispanic. Participants had an average HbA1c of 5.9% (48 mmol per mole).
Participants were monitored for new diabetes, with blood tests performed every 6 months for a median of 2.5 years.
The primary outcome was a diagnosis of early diabetes, based on an annual glucose test of fasting blood glucose, HbA1c and blood glucose after 2 hours, and a biannual badysis of fasting blood glucose and blood glucose. 39; HbA1c.
After 2.5 years of follow-up, 293 participants in the vitamin D group and 323 patients in the placebo group (respectively 9.39 events and 10.66 events per 100 person-years) had developed diabetes, said Pittas.
Thus, no significant difference was found in the development of diabetes between patients taking vitamin D supplementation and those taking placebo, for a risk ratio (HR) of 0.88 (95% confidence interval). [CI]0.75 – 1.04; P = .12).
At 24 months, the mean serum 25-hydroxyvitamin D in the vitamin D group was 54.3 ng per ml (compared to 27.7 ng per ml initially) compared to 28.8 ng per ml in the placebo group (from 28.2 ng per ml initially). .
The incidence of adverse events did not differ significantly between the two groups, including hypercalcemia, a fasting calcium-creatinine ratio above 0.375, an estimated glomerular filtration rate, and nephrolithiasis.
In the vitamin D supplementation group, 135 participants stopped taking their pill, 15 started taking a diabetes medicine and 7 started taking a medicine to lose weight. The equivalent numbers in the placebo group were 107 discontinued, 19 and 10 respectively.
"We performed an exploratory protocol-by-protocol badysis to determine whether, excluding patients taking medications or taking vitamin D supplements out of the test protocol, exceeding the 1000 IU test limit by day, had a positive impact. "
"We found that the primary endpoint was 22.0% in the vitamin D group and 25.1% in the placebo group with a risk ratio of 0.84 [95% CI, 0.71 – 1.00]"Explained Pittas.
Finally, Pittas noted that, in the American population, "the proportion of people suffering from vitamin D deficiency has improved in recent years; however, the proportion of people suffering from vitamin D deficiency has improved in recent years; Vitamin D has remained stable, paving the way for new research based on existing data. "
Effect of vitamin D supplementation in people with an unknown deficiency
Wexler, in his editorial, notes that the observed CF of 0.88 for the primary endpoint of the trial does not rule out a modest benefit of vitamin D. A larger and larger test long might be necessary to show a significant advantage in a population rich enough in vitamin D, she explains.
Wexler adds that the effect could be greater if vitamin D supplementation were given to people who were actually vitamin D deficient, compared to D2d participants who, in most cases, did not receive it. have not done.
In the United States, "the correlates of vitamin D deficiency include advanced age, black race, Asian or Hispanic race, and obesity," among other factors.
"Indeed, in the D2d trial, a post hoc Analysis of data from the 103 participants with vitamin D deficiency (<12 ng / ml) showed a risk ratio for [new-onset] Diabetes with vitamin D supplementation of 0.38 (95% CI, 0.18 to 0.80) ", compared to placebo, she says.
But Wexler adds that, overall, in a prespecified subgroup badysis in those who did not have sufficient levels, "the risk ratio among level participants [of vitamin D] less than 20 ng / ml was essentially the same as that observed in participants with a "sufficient" level of 20 ng / ml or more (0.87 and 0.89, respectively). "
Pittas noted that other major trials conducted in Japan, the United States, and Norway showed HR rates similar to those of the D2d trial, in the range of 0.87 to 0.9. .
NEJM. Published online June 7, 2019. Presented at Scientific Sessions of the American Diabetes Association 2019, June 7, 2019: Abstract.
Pittas did not reveal any relevant financial relationship. Wexler sits on the Data monitoring committee for oral semaglutide, Novo Nordisk.
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