Background

Vitamin D is essential for bone and muscle health. Vitamin D refers to both D3 (cholecalciferol) and D2 (ergocalciferol) - D3 is produced in the skin through the action of UVB in sunlight, it is the most common form in food and the form available in supplements (see photoboard). Mushrooms contain small amounts of D2. 

Sunlight is the most important source of vitamin D, and is estimated to provide 90% of vitamin D in humans.¹

• The amount of UVB available for skin synthesis varies with latitude, season, time of day, shade, and skin exposure (e.g. clothing). Window glass blocks UVB. There may not be enough UVB during winter months in the Southern states to maintain adequate vitamin D levels.
• Adults with dark skin require 2-7 times the amount of UVB compared to people with light skin to produce similar vitamin D levels.² There are no data on skin synthesis in children. Sunscreens do not result in low vitamin D with normal use in adults. See: Cancer Council Australia Position statement on sun exposure and vitamin D.

Diet is usually a poor source of vitamin D most Australians only get around 10% of their vitamin D from dietary sources.³

• Vitamin D is found naturally in few foods (some fatty fish, liver, small amount in eggs). Some dairy products are fortified with Vitamin D (some milk, all margarine).
• Breastmilk contains almost no vitamin D (25 IU/L). Infant formula is fortified with D3 (360-520 IU/L and higher in pre-term formula).

25(OH)D is used to measure vitamin D status. The recommended 25(OH)D level is >= 50 nmol/L at all ages and during pregnancy/lactation.

• RCH uses a chemiluminescence assay with ~10% variation. Around 1 mL blood (200 mcL serum) is required for analysis.
• To convert nmol/L to ng/mL divide by 2.5.

In the absence of sun exposure, recommended intakes are:⁴

• 12 months - adequate intake (AI) 400 IU daily.
• 1-18 years - estimated average requirement (EAR) 400 IU daily and recommended dietary allowance (RDA) 600 IU daily.

Risk factors for low vitamin D

• Lack of skin exposure to UVB in sunlight (time inside, chronic illness, complex disability, covering clothing, southerly latitude).
• Dark skin ( Fitzpatrick types V and VI).
• Medical conditions/medications affecting vitamin D metabolism (obesity, liver failure, renal failure, malabsorption, medications e.g. isoniazid, rifampicin, anticonvulsants).

In infants: exclusive breastfeeding AND any of - above risk factors, maternal vitamin D deficiency (cord levels ~65% maternal levels)⁵ or prematurity.

Prevalence

Refugee-background communities may have multiple risk factors for low vitamin D, e.g. dark skin, covering clothing and limited time outside.

• 61–100% of refugee background African Australians in Melbourne, Adelaide and Sydney have low vitamin D ( <50 nmol/L).^6–11
• Australian Health Survey data (2011-2013) found 36% of African Australians have low vitamin D ( <50 nmol/L) - noting <17% were from Victoria/Tasmania.¹²
• Two large Australian case series of rickets found almost all children had cultural risk factors (dark skin, maternal covering clothing).^13,14
• Low vitamin D is also seen commonly in other refugee cohorts wearing covering clothing (Afghani, Iraqi), and has been found in 33% of Karen refugees.¹⁵

Assessment

• Time outside, covering clothing, sunscreen use
• Dietary history - dairy intake, breastfeeding/formula in infants
• Previous vitamin D levels, previous/current treatment – see photoboard
• Family understanding
  
• Non-specific bony and/or muscular pain; fatigue with exercise
• Poor growth, irritability, delayed motor milestones (young children)
  
• Symptoms of low calcium (muscle cramps). Hypocalcaemic seizures are rare beyond 6-12 months of age.         
  
  
• Growth parameters, exclusion of other musculoskeletal pathology
• Fitzpatrick skin type
• Delayed fontanel closure (normally closed by 2 years)
• Delayed dentition (no teeth by 9 months, no molars by 14 months), enamel hypoplasia.
  
• Rickets – deformity in growing bones due to failure of mineralisation of osteoid. Peak incidence during infancy, although deformity reflects age/growth (and can be in any direction). Consider other causes if asymmetrical. Look for long bone deformity, splaying (wrists, ankles), bossing, delayed fontanel closure, rosary.         
  

Screening

• Screen children/adolescents with one or more risk factors for low vitamin D
  • Measure vitamin D, Ca, PO4 and ALP
  • Also measure PTH in those with low calcium intake, symptoms/signs or multiple risk factors

In exclusively breastfed infants with at least one other risk factor it is usually more practical to start supplements without screening. Consider checking levels (or adding daily supplements) in babies with risk factors for low vitamin D with mixed feeds or who have appropriately reduced their formula intake after starting solids. See photoboard

• Children with rickets: check vitamin D, Ca, PO4, ALP, PTH, Mg, UEC, urine Ca/PO4/Creatinine, X-ray wrist
  
  
• In recent arrivals: if the initial vitamin D level is normal, repeat at the end of the first winter in Australia
• Levels at the start and end of winter can be useful to make a clinical judgment on dosing
• Clinical photography is useful to monitor bony deformity (nutritional rickets usually corrects after treatment of low vitamin D provided the child has adequate calcium and phosphate intake).

Management – initial

• Admission symptomatic rickets/hypocalcaemia (including tetany, stridor, seizures) – these children may require intravenous calcium infusion and cardiac monitoring alongside management of low vitamin D (and exclusion of other causes) – do not give Vitamin D in the outpatient setting to this group.
• Urgent specialist assessment - children with clinical rickets or abnormal serum calcium.
  
  
• Children with low vitamin D should be treated to restore their levels to the normal range with either daily dosing or high dose therapy.
  • See dosing tables - there is limited evidence to support high dose therapy in children age <3 months. See photoboard for commercial formulations.
  • RCH uses 100,000 IU/ml D3 in olive oil. This solution is light and temperature sensitive and degrades to inactive vitamin D. The shelf life is 3 months if not kept in the fridge (with reduced potency at this time). It should be 90% potent at 3 months if stored <4 degrees C. 
• Ensure adequate calcium intake, and consider calcium supplements if dietary intake is poor (<2 serves dairy daily).
  • Cheese, yogurt and fortified soy dairy are alternatives for children who dislike milk.
  • 1 cup cow milk contains ~300 mg calcium. One Caltrate^TM tablet contains 600 mg calcium.  RDI for calcium by age
• Treatment should be paired with health education and advice about sun protection/sun exposure – encouraging outside play/activity. Children/young people with dark skin can tolerate intermittent sun exposure without sunscreen, although hats/sunglasses are still recommended. See Sunsmart handouts.
• Follow-up bloods at 3 months (earlier - at 1 month - in infants with moderate-severe deficiency) - 25(OH)D, Ca, PO4 and ALP; also PTH if elevated initially

Self-management long-term

• Breastfed babies with at least one other risk factor for low vitamin D should be given 400 IU daily for at least the first 12 months of life.
  • Babies on full formula feeds should receive adequate vitamin D from this source. 
  • Consider adding 400 IU daily in babies with risk factors for low vitamin D with mixed feeds or who have appropriately reduced their formula intake after starting solids. See photoboard
• Children/young people with ongoing risk factors for low vitamin D need to understand this is a long-term issue – they require ongoing monitoring and a plan to maintain vitamin D and calcium status through behavioural change and self-management where possible, and supplementation where this is inadequate.
• Provide education and a plan for self-management e.g. 400-600 IU daily OR 3000-4000 IU once weekly over the cooler months (May–August). This provides the EAR/RDA and should avoid blood testing and the need for high dose therapy. 
• Translated handouts are available.
• Photoboard of available vitamin D supplements
  

Dosing table: Management of low vitamin D

Calcium

Sun exposure

References

• References