The restrictions currently in place in Australia to protect against COVID-19 mean that most people will be spending more time indoors than usual. For many, this will mean less time in the sun.
But getting enough sunshine is important as the sun helps our bodies to make vitamin D. Low levels of Vitamin D can cause many physical and health problems.
Vitamin D deficiency is common, with about 1 in 3 Australian adults (30%) being deficient in vitamin D . Vitamin D deficiency is even more common towards the end of winter and in early spring, particularly in southern states when 50% of the population may be low in vitamin D .
The combination of COVID-19 restrictions and winter means it is highly likely many people have vitamin D levels even lower than usual.
The relationship between sunshine and vitamin D
Sunlight is made up of three types of ultraviolet (UV) radiation – UVA, UVB and UVC. When UVB directly reaches our skin, it causes a natural reaction resulting in the synthesis of a Vitamin D precursor. This precursor is then converted into the active form of vitamin D.
Sunshine is our main source of vitamin D, as only a small amount is present in our diet.
So, what is Vitamin D and why is it important?
Vitamin D is actually a hormone rather than a vitamin. It helps the body absorb calcium in the intestine, which is essential for the growth of bones and keeping them strong.
Vitamin D also helps to regulate calcium and phosphate levels, which is important for many biological processes, including keeping muscles strong and healthy, strengthening the immune system, reducing inflammation and supporting good mental health.
Low levels of vitamin D can therefore cause many physical and health problems. These include:
- Bone and muscle conditions 
- Tooth decay and poor oral health
- Immune and inflammatory conditions 
- Atopic dermatitis
- Multiple sclerosis (MS)
- Dementia 
- Depression 
In children, low levels of vitamin D can also cause rickets – a condition characterised by delayed growth, poor motor skills, and skeletal deformities .
In pregnant women, low vitamin D levels have been associated with conditions such as pre-eclampsia, hypertension, cardiovascular diseases and pre-term labour .
How much sunshine should you be getting?
The amount of sun exposure needed to obtain healthy levels of vitamin D depends on your:
- Age – The ability to produce Vitamin D from UVB decreases with age.
- Skin pigmentation – Darker skin has higher amounts of melanin, which limits the body’s ability to produce vitamin D.
- Skin coverage – clothing that covers more skin results in less UVB exposure.
- Location and Season – UV levels are lowest in winter and in more southerly locations in Australia.
In winter, the most effective time to be exposed to the sun to produce enough vitamin D is in the middle of the day. UV levels are lower in winter than summer, so longer periods of sun exposure are recommended to ensure your body can make enough vitamin D. It is important to expose skin directly to sunlight, as UVB cannot travel through glass.
Use the table below as a guide to find out how much time in the sun you need in winter based on your location. The figures in the table are relevant for people with fair skin wearing winter clothing (skin exposure on hands, arms and neck). This means more time will be required for people with darker skin and those whose clothes provide greater skin coverage .
The colour code in the table refers to the minimum amount of time required in the sun in winter to produce healthy levels of vitamin D: Green – less than 30 minutes, yellow – between 30 and 60 minutes, blue – more 60 minutes. (table adapted from Reference ).
Balancing sunshine exposure
While it is important to get enough sun exposure to produce vitamin D, it is also important to avoid getting too much sun.
This is because UVA and UVB radiation in sunlight can cause skin damage, sunburn and increase the risk of skin cancer (malignant melanoma). This is why the Australian Cancer Council recommends minimising sun exposure when UV radiation is high (above 3 on the UV index) .
**If you have had skin cancer in the past or are at high risk of skin cancer, talk to your doctor about the best way to maintain your Vitamin D levels and keep your skin safe.
How to know if you are Vitamin D deficient
While there are no specific signs or symptoms of vitamin D deficiency, you may notice the following changes:
- Fatigue or lack of energy
- Bone pain
- Muscle weakness, aches or cramps
- Mood changes, such as feeling down or sad more often
- Appetite changes
- Increased feelings of irritability and hostility
- Decreased concentration
Your doctor can perform a blood test to assess your vitamin D levels and confirm whether you are vitamin D deficient. While sunlight is the most effective way to boost vitamin D, supplementation may be required. Your doctor can advise on the most appropriate way to treat low vitamin D.
You may be at higher risk of vitamin D deficiency if you are:
- Elderly, housebound or are in residential care
- Naturally darker-skinned
- Avoiding sun exposure for long periods by choice or for medical reasons
- Regularly wear clothing that covers most of your skin
- Overweight or obese
- Affected by other medical conditions that impact your ability to absorb vitamin D (such as kidney disease, liver disease, Cystic fibrosis. Crohn’s disease or coeliac disease).
- Babies of vitamin D deficient mothers are also at risk of vitamin D deficiency.
- Exposure to sunlight is essential for producing vitamin D.
- Vitamin D is important for your health and well-being.
- If you are staying indoors more than usual, consider spending some time outdoors in direct sun to boost your vitamin D level.
The medical content of this article has been reviewed by Professor Peter Ebeling AO. Professor Ebeling is Head of the Department of Medicine in the School of Clinical Sciences at Monash Health, Faculty of Medicine, Nursing and Health Sciences, past-President of the Endocrine Society of Australia and Medical Director of Osteoporosis Australia.
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