A new study by Chinese investigators suggests that deficiency in vitamin D and estradiol may play a synergistic role in metabolic syndrome. Published in Menopause, the report is the first to look at how the vitamin and hormone interact in relation to the constellation of conditions that increase risk of heart disease, stroke, and diabetes in postmenopausal women.
For the cross-sectional analysis, the authors assessed data from 616 postmenopausal women aged 49 to 86. They were not taking estrogen or supplements containing vitamin D plus calcium or had they done so in the 3 months preceding the study. Women taking hormone therapy and those with impaired liver or renal function also were excluded.
Information on medical history and lifestyle—including smoking status, body mass index, and blood pressure—was self-reported by the participants on questionnaires. Blood samples were collected after an overnight fast and tested for serum estradiol and vitamin D levels.
Prevalence of metabolic syndrome in the participants was 31.7%. Of the women, 50.6% were vitamin D-insufficient and 31.2% were vitamin D-deficient.
Higher levels of vitamin D were associated with a favorable lipid profile, blood pressure, and glucose level. Estradiol was negatively associated with cholesterol, triglycerides, and blood pressure. The adjusted odds ratio (OR) for metabolic syndrome increased with decreasing levels of vitamin D (OR = 2.19, 95% CI, 1.19-4.01 for comparisons of vitamin D-deficient versus sufficient; Pfor trend = 0.009). The association remained unchanged after further adjustment for estradiol levels. After stratified analysis by vitamin D status, low estradiol increased metabolic syndrome risk in women with vitamin D deficiency (OR = 3.49, 95% CI, 1.45-8.05 for the lowest versus highest tertile).
The authors noted that prevalence of low vitamin D status was higher than expected despite a favorable latitude, positing that high levels of air pollution in southern China may have resulted in less outdoor activity and reduced access to vitamin D-rich food. They also underscored that no cause-and-effect relationship can be inferred from their results because of the study’s observational design.