Vitamin D

Vitamin D deficiency is a significant health issue across the population, in particular pregnant women. For a country basked in sunny skies, the prevalence is surprisingly high with an average 30% of Australian adults, or 3 in 10, having inadequate levels.

Vitamin D is an essential fat-soluble vitamin that is vital for the creation of our skeletal framework and teeth. Vitamin D is also needed to help deposit important minerals such as calcium and phosphorus into our bones each day, which are needed to maintain their strength. By having a strong skeletal system this will help prevent bone diseases such as osteoporosis and osteomalacia, and decrease the risk of bone fractures later in life. Vitamin D also helps to regulate our calcium levels, as well as help our immune system, pancreas, intestines and colon function.

Why is Vitamin D especially important for my pregnancy?

Meeting the requirements for Vitamin D is vital as during pregnancy your growing baby depends entirely on your stores for their own Vitamin D. Vitamin D is transferred to your growing baby across the placenta and this increases steadily throughout pregnancy as their demand builds, peaking during the last trimester. By the time your baby is born, they must have enough Vitamin D stores to last them around six weeks.

Vitamin D is needed to help developing your baby’s skeletal system. Deficiencies in Vitamin D during pregnancy can have serious outcomes that include:

  • Childhood rickets – This is a bone disease whereby the skeletal structure is brittle, being composed of soft bones that lack in minerals. This can lead to structural deformities later in life, especially involving the pelvic bones.
  • Growth retardation – This refers to when certain parts of the baby either stop growing or grow at a much slower rate than other parts. This often involves the lower limbs, with a lower knee-to-heel length or ‘dwarfism-like’ effect seen.
  • Lower infant birth weight.
  • Hypocalcaemia of the newborn – This refers to abnormally low calcium levels in your newborn, and if a dangerously low level, this can lead to seizures.
  • Increases risk of childhood disease – There has been some linkage that Vitamin D deficiencies will predispose your child to developing type 1 diabetes mellitus, multiple sclerosis, rheumatoid arthritis, asthma and allergic rhinitis later in life.

Where do I get my Vitamin D from?

Our body obtains the majority or 90% of its Vitamin D requirements through sunlight exposure. When our skin is exposed to UV radiation, Vitamin D is produced by a complex interaction of molecules in our skin. Vitamin D can also be obtained from your diet however the food sources are very limited and only provide 5-10% of our Vitamin D needs. The vitamin also has a short half-life, which means that our body tends to break it down quickly and we can become deficient if not careful.

Women at high risk for Vitamin D deficiency include:

  • Little or no exposure to sunlight, or sun-avoiding behaviours – This has become more of an issue due to our awareness of skin cancer in Australia and personal behaviours to avoid sun exposure.
  • Very dark skinned women – These women require 3-6 times more sun exposure in comparison to lighter skinned women to achieve the same amount of Vitamin D, due to the high content of melanin in their skin which acts as a filter and reduces the production of Vitamin D.
  • Women who live in areas of lower latitude, including southern parts of Australia, where there is less sunlight exposure and more months of cooler weather.
  • Certain ethnic cultures and religions – This refers to cultures where women are required to clothe their entire body, resulting in very minimal exposure to natural sunlight.
  • Vegetarian.
  • Obesity – Vitamin D is a fat-soluble vitamin and dissolves amongst the large body pool of fat, making it more dilute within the body and less available for the skeletal system to use.
  • Sedentary lifestyle – Low levels of physical activity limit sunlight exposure as there is limited outdoor recreational activities, as well as increased risk of being overweight.

How do I know if I am Vitamin D deficient?

Vitamin D deficiency is defined as level of 25-hydroxovitamin D (25-OH Vitamin D) of less than 75nmol/L. Current national target levels for Vitamin D in pregnant Australian women are greater than 50 nmol/L and can be classed as:

  • Mild deficiency 30-49nmol/L
  • Moderate 12.5-29 nmol/L
  • Severe <12.5 nmol/L

Every pregnant woman is now offered Vitamin D screening as part of her routine antenatal care. A blood test to calculate your Vitamin D stores should be performed early in pregnancy with the rest of the routine blood tests.

If you are found to be Vitamin D deficient then you will be required to:

  •  Commence Vitamin D supplements – Each tablet provides your body with 1000IU daily, and are available as Ostelin Vitamin D, OsteVIt D or Blackmores Vitamin D.  Multi-vitamin supplements do contain Vitamin D, however only contain 400IU per tablet., If you are Vitamin D deficient then this will not be enough to correct your levels and the additional supplement will be required. A blood test should be repeated six weeks after commencing supplements to ensure your levels have improved.
  • Referral to a dietitian – A dietician will be able to help assess your diet and ensure that you are eating the correct foods, in particular looking at your calcium intake.
  • Newborn supplementation – Once born your baby should receive Vitamin D supplementation if you were deficient in pregnancy. This will be given as one single dose of Vitamin D syrup that will give your baby enough stores for 4 months. If you are going to breastfeed beyond this then your baby may require additional supplements as breastmilk contains less Vitamin D than that provided by formula feeds. This should be discussed with your family doctor.
  • Sunlight exposure – If you have moderately fair skin, walking outside with arms exposed for 6-7 minutes during either mid-morning or afternoon will provide you with enough Vitamin D. During winter this exposure should increase to 20-40 minutes walking time. These times however do on location, level of sun intensity and amount of skin exposed. Sun precautions must especially be taken in areas of high UV intensity such as northern Queensland.
  • Improve your diet – Very few foods contain Vitamin D and only compromise of 5-10% of our intake. Good sources include fish oils, fatty fish such as salmon, mackerel and herring, mushrooms, egg yolks and liver, as well as fortified products such as milk, juice and margarine.

The following table highlights some important Vitamin D rich foods to include in your diet.

Vit D content

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