Association of adherence to a Mediterranean diet with glycemic control and cardiovascular risk factors in youth with type I diabetes: the SEARCH Nutrition Ancillary Study

Background/Objectives

This study aimed to determine the association between a Mediterranean diet and glycemic control and other cardiovascular risk factors among youth with type 1 diabetes (T1D).

Subjects/Methods

Incident T1D cases aged <20 years at diagnosis between 2002 and 2005 were included. Participants were seen at baseline (N=793), 1-year (N=512) and 5-year follow-up visits (N=501). Mediterranean diet score was assessed using a modified KIDMED index (mKIDMED). Multivariate linear regression and longitudinal mixed model were applied to determine the association between mKIDMED score and log-HbA1c, lipids, blood pressure (BP), and obesity.

Results

In cross-sectional analyses using baseline data, for individuals with an HbA1c of 7.5%, a two-point higher mKIDMED score (one standard deviation) was associated with 0.15% lower HbA1c (P=0.02). A two-point higher mKIDMED score was associated with 4.0 mg/dL lower total cholesterol (TC) (P=0.006), 3.4 mg/dL lower low-density lipoprotein (LDL)-C (P=0.004), 3.9 mg/dL lower non-high-density lipoprotein (non-HDL)-C (P=0.004), and 0.07 lower LDL-C/HDL-C ratio (P=0.02). Using longitudinal data, a two-point increase in mKIDMED score was associated with 0.01% lower log-HbA1c (P=0.07), 1.8 mg/dL lower TC (P=0.05), 1.6 mg/dL lower LDL-C (P=0.03), and 1.8 mg/dL lower non-HDL-C (P=0.03) than would otherwise have been expected. HbA1c mediated about 20% of the association for lipids in both cross-sectional and longitudinal models. An unexpected positive association between mKIDMED score and systolic BP was found among non-Hispanic white youth in cross-sectional analyses (P=0.009). Mediterranean diet was not associated with obesity.

Conclusions

Mediterranean diet may improve glycemic control and cardiovascular health in T1D youth.

Vitamin D in youth with Type 1 diabetes: prevalence of insufficiency and association with insulin resistance in the SEARCH Nutrition Ancillary Study

AIMS

To determine the prevalence of plasma vitamin D (25-dihydroxyvitamin D) insufficiency in individuals with Type 1 diabetes and to determine the cross-sectional and longitudinal associations of plasma vitamin D with insulin resistance.

METHODS

Participants from the SEARCH for Diabetes in Youth Study [n = 1426; mean age 11.2 years (sd 3.9)] had physician-diagnosed Type 1 diabetes [diabetes duration mean 10.2 months (sd 6.5)] with data available at baseline and follow-up (approximately 12 and 24 months after baseline). Insulin resistance was estimated using a validated equation. Cross-sectional and longitudinal multivariate logistic regression models were used to determine the association of plasma vitamin D with insulin resistance, adjusting for potential confounders.

RESULTS

Forty-nine per cent of individuals had plasma vitamin D < 50 nmol/l and 26% were insulin resistant. In cross-sectional multivariate analyses, participants who had higher plasma vitamin D (65 nmol/l) had lower odds of prevalent insulin resistance than participants with lower plasma vitamin D (25 nmol/l) (odds ratio 0.70, 95% CI 0.57-0.85). This association was attenuated after additional adjustment for BMI z-score, which could be a confounder or a mediator (odds ratio 0.81, 95% CI 0.64-1.03). In longitudinal multivariate analyses, individuals with higher plasma vitamin D at baseline had lower odds of incident insulin resistance, but this was not significant (odds ratio 0.85, 95% CI 0.63-1.14).

CONCLUSIONS

Vitamin D insufficiency is common in individuals with Type 1 diabetes and may increase risk for insulin resistance. Additional prospective studies are needed to determine the association between plasma vitamin D and insulin resistance, and to further examine the role of adiposity on this association.