Anorexia Nervosa: vitamin D levels strongly influence bone mineral density and bone turnover markers in female during weight gain

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Anorexia nervosa (AN) is often associated with amenorrhea and an increased risk of impaired bone health due to low bone mineral density (BMD), failure to reach adequate peak bone mass during adolescence, and further bone loss in young adulthood.

Recent studies has demonstrated that weight restoration is currently indicated as the core strategy for increasing BMD in patients with Anorexia Nervosa.

As regards bone status in Anorexia Nervosa, we have recently shown that vita-min D (25-OH-D) deficiency is widespread in untreated patients, and that there is a strong positive correlation between vitamin D status and hip BMD.

An Italian study published on the International Journal of Eating Disorders investigated a potential role for vitamin D status on bone mineral density (BMD) during weight gain in 91 consecutive female patients with anorexia nervosa (AN) (age 13-45 years, weight 39,4 ± 5,6 kg, BMI 15,1 ± 1,6 kg/m²).

Spine and hip BMD assessed by dual-energy X-ray absorptiometry (DXA), serum vitamin (25-OH-D),N-propeptide of type I collagen (P1NP), C-terminal telopeptide of type I collagen (CTX), and intact parathyroid hormone (PTH) were measured before and after a 20-week intensive weight-restoration program in ninety-one female patients with eating disorder based on improved behavioral cognitive therapy (CBT-E).

Although weight and BMI significantly increased in all patients during treatment (BMI from 15,1 ± 1,6 kg/m² to 19,1 ± 1,2 p<0,001), mean BMD only significantly increased at the spine.

The increase in spine BMD was significantly higher only above post-treatment 25-OH-D levels of 30 ng mL-1.
There was a significant decrease in bone resorption (CTX; p 5 .043) and increased bone formation (P1NP; p < 0.001) after weight restoration.

Nevertheless, a significant increase in PTH was also found, which was inversely correlated with decreased post-treatment 25-OH-D levels (R2 = 0.153, p < 0.001).

According to these results, Hypovitaminosis D may counteract the efficacy of refeeding in AN through increased bone resorption mediated by secondary hyperparathyroidism, which strongly supports the use of vitamin D supplements for bone health in nervous anorexia and suggests that a serum dose of 30 ng ml-1 of 25-OH-D may be very useful to obtain the optimal level of PTH, bone resorption and BMD increase.