people who are overweight or who have obesity appear to have a sluggish reaction to Vitamin D A new analysis of randomized trials compared supplementation with normal-weight individuals.
“Something different seems to be happening with vitamin D metabolism at higher body weights, and this study may help explain the reduced results of supplementation in individuals with high body mass index (BMI). said first author Deirdre K. Tobias, ScD., an associate epidemiologist in Brigham’s Division of Preventive Medicine. She made the comments in a press statement issued with her study. publish online this week’s JAMA network open.
The findings are from a post-hoc analysis of the Large Vitamin D and Omega-3 Trial (VITAL), which in its entirety was randomized to vitamin D supplementation (2000 IU/day) for 5 years. No benefit was seen compared to people and placebo. Primary endpoint term for cancer or major cardiovascular disease outcome.
However, prespecified secondary analyzes according to body weight showed normal weight (BMI < 25.0 kg/m2) had significant benefits from supplementation compared to placebo with respect to cancer incidence (24% reduction), cancer mortality (42% reduction), and autoimmune disease (22% reduction). , overweight or obese.
The new analysis adds important context to the trial’s overall findings, said Katherine N. Bachmann, MD. Accompanying editorial.
“Thanks to its very large sample size and detailed biomarker analysis, the current study suggests that overweight and obese people may be less responsive to vitamin D supplementation, which may contribute to the different results with BMI. We can provide new evidence that there is…in the original VITAL,” she wrote.
“To determine the optimal dosage or circulating vitamin D levels for non-skeletal health-related outcomes in obese patients,” said Bachman of the Department of Diabetes, Endocrinology, and Metabolic Sciences at Vanderbilt University Medical Center in Nashville, Tennessee. Further research is needed,” he added.
New analysis looked at baseline and 2-year vitamin D and biomarkers
To examine specific changes in vitamin D serum and biomarker levels between different weight groups, Tobias and colleagues analyzed data from the trial’s 16,515 participants (out of the 25,000 originally included in VITAL). and examined changes in key vitamins. D Baseline and follow-up serum levels and biomarkers.
Consistent with the general observation of decreased vitamin D levels with obesity, participants in the higher BMI category had graded pre-randomization mean serum total 25-hydroxyvitamin D (25-OHD) levels. levels were in the range of 32.3 ng/mL in normal body weight. 28.0 ng/mL (P. < .001 (for linear trend)).
Baseline levels of other vitamin D biomarkers such as total 25-OHD3, free vitamin D (FVD) and bioavailable vitamin D (BioD) were also lower with higher BMI.
Of the 2,742 participants with repeat blood sampling at year 2, a significant mean increase in serum 25-OHD levels (11.9 ng/mL) in participants randomized to vitamin D supplementation was observed at the end of the study period. observed as a whole. Placebo group (-0.7 ng/mL).
There was also little or no change in the placebo group, and overall, mean total 25-OHD, 25-OHD3, FVD, and BioD levels significantly increased over the two years among those who received supplementation.
However, when stratified by BMI level, those with higher baseline BMI had lower magnitudes of increase (interaction of all treatment effects P. < .001). For example, with a BMI <25.0 kg/m, his 2-year mean increase in total 25-OHD levels for supplement and placebo was 13.5 ng/mL.2 Only 10.0 ng/mL for BMI ≥ 35.0 kg/m3, whereas2.
Importantly, even after controlling for baseline vitamin D adequacy or deficiency status, BMI was significantly associated with changes seen with supplementation.
“It is surprising that people with high BMI respond poorly to supplementation even when their vitamin D levels are low, and the interaction of supplements with BMI and health outcomes is not simply due to higher prevalence of deficiency. It suggests that Medscape Medical News.
“Even if baseline levels are inadequate or low, people with high BMI do not appear to be able to catch up to adequate levels as well as those with normal BMI.”
mechanism?
Among the prevailing theories as to why high BMI is associated with lower serum vitamin D levels and less responsiveness to supplementation, vitamin D is a fat-soluble vitamin, and therefore higher BMI is associated with increased obesity and fat storage capacity, There are some that increase the removal of vitamin D. vitamins from circulation.
“Our results are largely consistent with this hypothesis,” the authors said.
They add weight loss studies, including related bariatric surgeryfurther showing significant increases in serum 25-OHD or circulating vitamin D levels after weight loss compared to baseline.
Other theories suggest that obesity-induced liver dysfunction may contribute to impaired vitamin D metabolism.
Tobias noted that because the exact mechanism is not clearly understood, the potential for addressing low vitamin D levels, for example, by taking high-dose supplements in obese people, remains unclear.
“Once we have more clarity on what the mechanism is, I think it makes sense to look at the doses needed to achieve the desired body levels.
The VITAL study was funded by grants from the National Center for Complementary and Integrative Medicine and other funding sources. Full disclosure of the authors is detailed in the published study.
JAMA net opened. Published January 17, 2023. overview, editorial
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