What is Vitamin D?
Vitamin D is often called the 'sunshine vitamin' as it can be obtained both through the food we eat and by producing it in our skin when we're exposed to sunlight (UVB rays). Only when we have insufficient exposure to sunlight, do we become dependent on our diet for Vitamin D.
Vitamin D is an important nutrient because one of its major roles is to ensure we have the right amounts of calcium circulating in our bodies. It does this by influencing how much calcium we absorb from the foods we eat. That's why Vitamin D and Calcium are very important for building and maintaining strong, healthy bones.
Vitamin D also helps boost our immune system, reduce inflammation, maintain muscle strength, regulate blood sugar, and protect against some cancers.
Vitamin D deficiency in Australia
For Australians, the main source of Vitamin D is through exposure to sunlight. How much sunshine we are exposed to, and therefore the amount of Vitamin D we produce in our skin, is determined by where we live; for example some countries in the northern hemisphere have more cloud cover and longer winters and so see less of the sun and their inhabitants produce less vitamin D. Ironically, despite the large amount of sunshine in Australia, many Australians are Vitamin D deficient.
These deficiencies often occur in:
- The elderly, whose skin produces less vitamin D - particularly those who live in nursing homes
- People with darker skin colouring who need longer exposure to the sun to produce sufficient amounts of Vitamin D
- People who wear full body coverings, for religious reasons
- People who have skin conditions that require them to avoid exposure to sunlight
Deficiency can also result from kidney and/or liver disease where the body is unable to produce the active versions of Vitamin D and where there is inadequate absorption of vitamin D from food.
Signs and symptoms
Vitamin D deficiency can have many effects. A very obvious sign is soft bones in both children (rickets) and adults (osteomalacia). In children, this commonly leads to bowed legs. In adults vitamin D deficiency can be one of the causes for osteoporosis which is a condition of lower bone density which can increase the risk of broken bones and spine compression. Deficiency can also lead to a weakened immune system, more inflammatory and autoimmune diseases, weak muscles, diabetes and some recent research suggests that D levels have a relationship with cognition in older adults.
What's the recommended daily intake of Vitamin D?
The recommended dietary intakes in the table are from the Nutrient Reference Values. 2006 and are based on adequate intakes for people who do not have sun exposure.
Recommended Dietary Intake: Vitamin D
|Infants: 0-12 months||5ug|
|Children: 1-8 yrs||5ug|
|Boys: 9-18 yrs||5ug|
|Girls: 9-18 yrs||5ug|
|Adults: 19-50 yrs||5ug|
|Adults: 51-70 yrs||10ug|
|Adults: Over 70 yrs||15ug|
Sources of Vitamin D
It is quite difficult to get sufficient Vitamin D from food alone, as few foods naturally contain Vitamin D. Food only provides about 2-3ug/day. Oily fish such as salmon, sardines, mackerel and herring are good sources. Other sources include eggs (yolk), dairy, margarines and some other foods which have vitamin D added.
|Foods||Serve size||Vitamin D content (ug)|
|Eggs||2 Large eggs||0.8|
|Margarine (vitamin D added)||2 teaspoons||1.0|
|Milk (vitamin D added)||250ml (1 glass)||1.3|
Table: Vitamin D content of foods
For Australians, the main source of Vitamin D is through exposure to sunlight.
How many minutes should I spend in the sunshine?
Health authorities warn us to limit our exposure to the sun due to the increased risk of sun burn which is a risk factor for skin cancer. The risk of burning is greater when UV levels are greater in summer and near the middle of the day. However we do not need much time in the sun to be able to make enough vitamin D.
The time we need in the sunshine will depend on the time of year and where we live. To care for our skin the sun exposure needs to be during the UV safe time of day. The sun is stronger in summer and near the equator so the Cancer Council Australia recommends that in summer: we expose our face, arms and hands or the equivalent area of skin to a few minutes of sunlight on either side of the peak UV periods (avoid between 10am and 3pm) on most days of the week.
In in the southern regions of Australia in Winter when UV radiation levels are less intense, maintenance of vitamin D levels may require 2-3 hours of sunlight exposure to the face, arms and hands or equivalent area of skin over the course of a week. (see Cancer Council How Much Sun is Enough http://www.cancer.org.au/File/Cancersmartlifestyle/Howmuchsunisenough.pdf)
Can I have too much Vitamin D?
Excessive exposure to sunlight does not lead to excessive Vitamin D levels in the body, however, large doses of Vitamin D supplements should be taken with care as they can cause unpleasant and possibly toxic side effects. Consult your GP or other health care professional for further advice.
This fact sheet contains general information and is not intended as a substitute for medical advice. Please consult your healthcare professional for specific advice for your personal situation.
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Vitamin D Intake Australian Children: Source: 2007 Australian National Children's Nutrition and Physical Activity Survey