Strong relationship between vitamin D status and bone mineral density in anorexia nervosa

Anorexia nervosa (AN) is associated with impaired bone health and low bone mineral density (BMD) as a consequence of an inadequate peak bone mass in adolescence and bone loss in young adulthood. The vitamin D status with its implications for bone health in patients affected by AN has only been examined previously in small studies.

To evaluate the prevalence of vitamin D deficiency and test the hypothesis that patients with AN and vitamin D deficiency might have worse bone metabolism and lower bone density as compared with AN with adequate vitamin D repletion.

We analysed the vitamin D status and bone metabolism in a large cohort (n=89) of untreated patients affected by AN, with amenorrhoea.

Vitamin D deficiency is widespread in untreated patients with AN: 16.9% had 25OH vitamin D levels below 12 ng/ml, 36% below 20 ng/ml and 58.4% below 30 ng/ml. PTH values were higher and BMD at both femoral sites were lower in patients with vitamin D<20 ng/ml. Progressively higher values of BMD were observed by 4 ranks of 25 OH vitamin D values (severe deficiency: <12 ng/ml, deficiency: ≥12 ng/ml and <20 ng/ml, insufficiency: ≥20 and <30 ng/ml and normal: ≥30 ng/ml). In patients with severe vitamin D deficiency BMD at the hip were significantly lower than that measured in groups with values over 20 ng/ml (p<0.001 for trend). The level of significance did not change for values adjusted for BMI or body weight.

We found a strong relationship between vitamin D status and hip BMD values with additional benefits for those with 25OHD levels above 20 ng/ml. Our results support the design of a randomized placebo-controlled clinical trial on the effect of vitamin D on BMD in patients with AN. The second point, whether 25OHD should be above 20 or 30 ng/ml remains a discussion point.