Researchers published the study covered in this summary on Research Square as a preprint that has not yet been peer reviewed.
Key Takeaways
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Data from five sequential National Health and Nutrition Examination Survey (NHANES) reports using US population samples in 2009-2018 showed each 1 unit increase in serum levels of vitamin D3 (25-hydroxyvitamin D3) (measured as nmol/L) was significantly associated with an 11% lower risk of developing insulin resistance.
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This association between higher serum vitamin D3 levels and a reduced risk for insulin resistance was strongest in people with a body mass index (BMI) of 24 to 28 kg/m2 (overweight). The association was weaker in people with BMIs below and above this range.
Why This Matters
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Vitamin D3 deficiency is common worldwide.
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The findings further strengthen the understanding of insulin resistance in the context of widespread vitamin D3 deficiency and suggest that vitamin D3 supplementation might reduce insulin resistance and prevent development of diabetes in the general US population.
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Previous studies examining the connection between vitamin D3 and insulin resistance have focused on patients with diabetes, whereas this study used data from the general US population.
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The authors say this is the first study to find that BMI influences the strength of interaction between vitamin D3 levels and insulin resistance.
Study Design
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Researchers analyzed data from 49,694 participants in five consecutive NHANES cycles from 2009 to 2018, and from this cohort they examined data from 2746 people age 18 and older; had data for vitamin D3, fasting insulin, and fasting glucose; did not have diabetes, hypertension, hypercholesterolemia, or hyperuricemia; and met several other inclusion and exclusion criteria
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They estimated insulin resistance using homeostasis model assessment of insulin resistance (HOMA-IR), which is equal to fasting insulin (μU/mL) times fasting glucose (mmol/L) divided by 22.5.
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Insulin resistance was defined as HOMA-IR ≥ 2.6 and the absence of IR as HOMA-IR < 2.6.
Key Results
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862 participants had insulin resistance and 1884 participants did not have insulin resistance.
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Participants were an average age of 35 years old, and 44% were men.
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Median vitamin D3 level, measured by liquid chromatography-tandem mass spectrometry, was 50.9 nmol/L in those with insulin resistance and 58.5 nmol/L in those without insulin resistance.
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In the fully adjusted multivariable model, patients had a significant 11% lower rate of prevalent insulin resistance for each 1 unit increase in serum vitamin D3.
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Among patients with a BMI of 24 to 28 kg/m2, each 1-unit increase in vitamin D3 was associated with a significant 20% reduction in the risk of insulin resistance. People with BMI levels below or above this range did not show a significant link between serum vitamin D level and insulin resistance.
Limitations
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The cohort examined did not include enough nonsmokers to determine whether smoking affects the link between insulin resistance and vitamin D3 levels.
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The study excluded people with hyperlipidemia, hyperglycemia, and hyperuricemia, and so the findings are not generalizable to the entire US population.
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It remains unclear how genetics might impact the relationship between vitamin D3 levels and risk of insulin resistance, as this was not included as part of the analyses.
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HOMA-IR does not provide reproducible nor fully accurate measurements of insulin resistance.
Disclosures
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The study did not receive commercial funding.
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The authors report no relevant financial disclosures.
This is a summary of a preprint research study, “The association between the level of vitamin D3 and insulin resistance in the general adult population of the United States: A cross-sectional study based on the NHANES database,” by researchers from Qinghai University, Xining, China. Preprints from ResearchSquare are provided to you by Medscape. This study has not yet been peer reviewed. The full text of the study can be found on researchsquare.com.
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