Essential Vitamins & Minerals /

Vitamin D

01 In Brief

Vitamin D is an essential, fat-soluble vitamin that is predominantly derived from exposure to sunlight. Dietary intake alone is not enough to meet your daily requirements. Sun-smart policies have heightened the risk of Vitamin D deficiency. This risk increases in women with dark skin or who are veiled. Many women enter pregnancy vitamin D deficient. The fully breast fed newborn baby depends on maternal vitamin stores until 9-12 months of age as they have little sun exposure during this time. Infants who are Vitamin D deficient are at risk of rickets and low calcium in the newborn period, and there is also evidence that bone mineral is low later in childhood. Women should have their Vitamin D levels measured pre-pregnancy or in early pregnancy to determine if supplements are needed.

02 What Do I Need To Know?

• Vitamin D is a fat-soluble vitamin which is essential for healthy bones. There are two forms of Vitamin D: D2 and D3. Both are metabolised in the liver to 25 Hydroxy Vitamin D2 and D3. The hydroxy forms are measured when a blood test is ordered. 

• Humans derive 80 per cent of their Vitamin D from sunlight. Vitamin D3 is formed in the skin after exposure to sunlight and is also is present in fatty fish. Other sources include eggs, meat and fortified foods such as margarine. For most Australians adequate intake is unlikely without fortified foods. The daily requirement is around 800-1000 IU per day. 

• Sun-smart policies aim to decrease skin cancer but have the undesirable effect of decreasing sun exposure and hence the amount of Vitamin D that is formed in the body. There is now considerable debate about how much exposure to sunlight is advisable in order to balance the need for adequate vitamin D levels, whilst avoiding the risk of sun damage. People with darker skin need three to four times more sunlight exposure than lighter skinned people. Getting enough Vitamin D becomes even more problematic if the skin is always entirely covered by clothing.

• Recommended sun exposure, (before you put your sunscreen on), has been estimated by the expert panel of the Australian and New Zealand Bone and Mineral Society (see reference below). Recommendations vary in summer from 6-7 minutes per day in far north Queensland to 7-9 minutes in Tasmania and in the winter 9-12 minutes in far north Queensland to 40-47 minutes in Tasmania.

• Vitamin D deficiency is often asymptomatic but is associated with muscle aches and pains and an increased risk of fracture. Blood tests measures 25-Hydroxy Vitamin D, and a level below 50 nmol/l is considered to be deficient.

• There is considerable debate about what the optimal dose of extra vitamin D should be for pregnant women. The amount of 400 IU in most pregnancy supplements is probably insufficient for those who do not get enough sun exposure. It is best to ask for a pre-pregnancy level to be taken so that your doctor can assess your requirements.

VITAMIN D DEFICIENCY IN THE NEWBORN

• The fetus is dependent on the mother's levels of vitamin D to prevent rickets and low blood calcium at birth. The fetus stores vitamin D in utero but during the first nine months after birth these stores decrease due to inadequate sun exposure and the fact that breast milk is a poor source of Vitamin D.

• If the mother is Vitamin D deficient during pregnancy it is recommended that the baby receive a supplement for the first 12 months e.g. Pentavite® Bayer Healthcare 0.45 ml daily (contains 400IU). It takes at least 12 months for stores to be replenished, so even if supplements are taken during pregnancy and the blood level is normal, supplementing breast fed babies is still recommended. In high-risk infants a single dose of 50,000 units of ergocalciferol, a form of Vitamin D, may be given as an alternative.

• Rickets is a bone disorder that develops as result of severe Vitamin D deficiency in infants and children. It is characterised by fractures, bone pain and deformities of the wrists and ribs, and bowing of the tibia. If severe it is also characterised by low blood calcium in the newborn.

• The American Academy of Paediatrics Vitamin D Deficiency Clinical Report currently recommends that all breast fed infants and infants receiving less than 27-32 oz (800-950ml) of formula per day be supplemented with Vitamin D drops regardless of the maternal level. In Australia most pregnant women are now screened in pregnancy. However, anyone can request to have a Vitamin D test.
  

03 What Others Say

• Royal Women's Hospital fact sheet :

Vitamin D and Pregnancy

• Raising Children Network

VitaminD: what you need to know

• Children, Youth and Women's Health Service South Australia

Fact sheet on Vitamin D and pregnancy  

• Better Health Channel 

Fact sheet  - Rickets

04 I Want To Know More

• Excellent summary from Australian Prescriber magazine 

Australian Prescriber article on bone health

• Article from archives of diseases of children regarding Vitamin D levels in pregnancy 

Vitamin D in pregnancy: an old problem still to be solved

• American Academy of Pediatrics

Vitamin D Deficiency Clinical Report

• Royal Australasian and New Zealand College of Obstetricians and Gynaecologists

Statement on Pre-pregnancy counselling and routine antenatal assessment in the absence of pregnancy complications

• Vitamin D test from LabTests on line

Pathology Vitamin D test

05 Clinicians Tools and Resources

Vitamin D Deficiency in Victoria: guidelines for treatment

• Vitamin D and adult bone health in Australia and New Zealand 

A position statement from the working group of the Australian and New Zealand Bone and Mineral Society, Endocrine Society of Australia and Osteoporosis Australia.

VIC NETS Handbook

Vitamin D: Dot Point Summary

Last updated: 12/07/2011 by Dr Elizabeth Hallam*/Claire Galea

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