Abstract

• Rickets is a childhood disease characterised by lower limb and chest deformities, stunted growth and, in some cases, seizures. Its main cause is calcium deficiency due to deficiency in vitamin D, a factor that enhances intestinal calcium absorption.
   
• To identify the safest and most effective strategies for preventing rickets due to vitamin D deficiency in France and other Western European countries located at the same latitudes, we reviewed the available literature using the standard Prescrire methodology.
  
  
• In Western Europe and North America, the incidence of rickets fell sharply during the 20th century, following an increase in milk consumption and widespread vitamin D supplementation in the form of cod liver oil, medications, and fortified foods.
   
• Since the 1980s, rickets in these countries has mainly affected breastfed children under the age of 5 years with dark skin. A few cases have also been reported in dark-skinned adolescents.
   
• The main source of vitamin D is cutaneous synthesis stimulated by solar ultraviolet B radiation. Between 2 and 3 hours of sunlight exposure per week appears sufficient to meet vitamin D requirements in fair-skinned infants. Dietary vitamin D intake is generally very low, except in infants fed with infant or follow-on formula milk fortified with vitamin D.
   
• We found four published intervention trials with clinical endpoints conducted in the northern hemisphere above the 38th parallel. Two of these trials suggested that daily supplementation with 400 IU of vitamin D prevented rickets in children less than 3 years old.
   
• Most comparative trials have assessed the efficacy of vitamin D supplementation by measuring the blood concentration of 25-hydroxyvitamin D, which correlates only weakly with the risk of clinical rickets. However, a 25-hydroxyvitamin D concentration above 20 ng/ml appears to protect against rickets.
   
• Many randomised trials have shown that this blood concentration is reached with daily vitamin D doses of 400 IU in most children under 1 year of age and 600 IU to 750 IU per day in children aged over 1 year. Vitamin D2 (ergocalciferol) and vitamin D3 (colecalciferol) appear to have similar biological potency.
   
• Profound vitamin D deficiency during pregnancy sometimes leads to early-onset rickets in the child. Conversely, hypercalcaemia was reported in newborns whose mothers had taken dietary supplements containing vitamin D.
   
• In children less than 1 year old, daily intake of 800 IU or more of vitamin D carries a risk of hypercalcaemia and hypercalciuria. As a precaution, it is best to avoid giving periodic massive doses to these children.
   
• Serious syncope-like reactions were reported in France in infants given the Uvestérol° line products.
   
• In many countries, the recommended daily vitamin D intake for infants less than 9 months old is 400 IU. The French Society of Paediatrics recommends higher intake, but this advice is not based on clinical trial data.
   
• In practice, vitamin D supplementation is warranted for all infants aged less than 1 year. Children with dark skin who receive little sunlight should continue supplementation until the age of 5 years and again in adolescence. Supplementation also seems to be warranted for pregnant women with dark skin or little sunlight exposure. 

©Prescrire 1 March 2014

"Preventing rickets with vitamin D. Supplementation for some children" Prescrire Int 2014; 23 (147): 73-78. (Pdf, subscribers only)