Endocrine Abstracts

Background and objectives: Vitamin D deficiency and insufficiency is common in obese individuals. We aimed to determine the prevalence of vitamin D insufficiency within a cohort of severely obese individuals, exploring potential underlying associations.

Methods: In a retrospective analysis of 703 patients sequentially presenting for bariatric surgery assessment, 663 had complete demographic, anthropometric, and haematological measures (vitamin D, folate, vitamin B₁, vitamin B₁₂, white cell count, and C-reactive protein). Vitamin D levels were defined as deficient (<25 nmol/l), insufficient (25–50 nmol/l), or normal (>50 nmol/l). Adiposity was estimated using indirect measures; BMI, and body fat percentage (BF%) estimated via the CUN-BAE equation. Statistical analyses: groups formed according to vitamin D status were compared using ANOVA. Stepwise regression was performed using age, gender, BMI, BF%, index of multiple deprivation, multivitamin use, number of comorbidities, white cell count, C-reactive protein, folate and vitamin B₁₂ as independent variables for vitamin D concentration.

Results: Mean serum vitamin D concentration was 38±23 nmol/l. 75% of patients had abnormal serum vitamin D concentrations; 33.2% were deficient, and 41.8% insufficient. Individuals were divided according to vitamin D status (deficient vs insufficient vs normal). Those with vitamin D deficiency had an increased BMI (48.6 vs 46.9 vs 45.4 kg/m²; P<0.001), decreased folate concentrations (5.8 vs 7.7 vs 8.7 ng/ml; P<0.001), and decreased vitamin B₁₂ concentrations (393 vs 445 vs 464 pg/ml; P=0.003). Stepwise regression revealed only a weak association with folate concentration (R²=0.081; P=0.046).

Conclusion: Vitamin D insufficiency is common among severely obese bariatric surgery candidates, observed in approximately 75% of patients. The underlying cause is still unknown and the hypotheses of sequestration within adipose tissue, or inadequate nutritional intake are not supported by these data. Questions remain regarding the functional significance of low vitamin D concentrations among obese individuals, and whether routine supplementation is required.