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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Public Health

Year Degree Awarded

Summer 2014

First Advisor

Dr. Alayne Ronnenberg

Second Advisor

Dr. Elizabeth Bertone-Johnson

Third Advisor

Dr. Richard Wood

Fourth Advisor

Dr. Carol Bigelow

Subject Categories

Public Health | Women's Health

Abstract

We conducted a cross-sectional analysis among 270 (18- to 30-year old) female participants in the UMass Amherst Vitamin D Status Study (n = 270) to assess the extent to which dietary intakes of calcium and vitamin D are associated with obesity markers. We also evaluated the association between serum 25-OHD concentrations and both adiposity and inflammatory biomarkers. Study participants were mostly Caucasians (84.5%) with normal BMI, although about half of women had high adiposity (total body fat ‘TBF’≥ 32%). Women reporting adequate intakes of calcium (≥ 1000 mg/day) but low intakes of vitamin D (< 600 IU/day) were more than twice as likely to have a high percentage of TBF compared to women with adequate intakes of both calcium and vitamin D. In addition, women with lower calcium intake from supplements were twice as likely to have a waist circumference ≥ 80 cm (OR = 2.04; 95% CI: 1.04 – 3.99) compared to women in the highest tertile of calcium intake. The magnitude of this association is important since among young women 18-30 years old, a waist circumference greater than 80 cm indicates central obesity and suggests increased visceral adiposity, which contributes to hyperlipidemia and other obesity-related chronic conditions. Among all women, total vitamin D, food vitamin D, and supplemental vitamin D intake were not associated with serum 25-OHD concentration (P > 0.05). However, among supplement users only, intake of vitamin D supplements was positively correlated with serum 25-OHD levels (ß = 0.03 ± 0.01 nmol/L, P = 0.05). These findings support the notion that serum levels of 25-OHD are influenced by other factors besides the vitamin D content of foods, including the use of vitamin D supplements. Serum 25-OHD concentration tended to be correlated with hs-CRP levels (r = 0.14, P = 0.06), but was not significantly associated with adiposity and inflammatory biomarkers. Among women with low 25-OHD (< 75 nmol/L), serum 25-OHD level was inversely associated with IL-2 and GM-CSF concentrations, and marginally associated with IL-6 and IL-7 concentrations. Additional prospective studies in more heterogeneous populations will help to characterize the relationship between vitamin D status, inflammation and obesity.

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