Vitamin D Deficiency: Why It's So Common in Australia and What to Do About It

Why Vitamin D Matters

Vitamin D is essential for calcium absorption, which makes it critical for bone strength. Without enough of it, bones can become thin and brittle over time, increasing the risk of osteoporosis and fractures in adults and causing a condition called rickets in children. But its role extends well beyond bones. Vitamin D supports muscle function, immune health, and mood regulation. There is growing evidence linking low vitamin D to increased susceptibility to infections, poor wound healing, and fatigue.

For pregnant women, adequate vitamin D is particularly important. It supports the baby's bone and brain development and is associated with better outcomes for both mother and child. Breastfed infants whose mothers are deficient are also at risk, as breast milk alone is not a reliable source of vitamin D.

Why Australians Are Still Deficient

The paradox is largely explained by sun protection behaviour, and this is the right behaviour. Given Australia's extremely high rates of skin cancer, deriving all your vitamin D from unprotected sun exposure would be a genuinely harmful strategy. The result is that many Australians, quite reasonably, avoid the midday sun, use sunscreen consistently, and cover up outdoors, which limits the skin's ability to synthesise vitamin D.

Several other factors compound this. Many Australians spend most of the day indoors, particularly those in office-based work. In southern cities like Sydney and Melbourne, the sun's angle during winter months means UVB radiation is too weak for much of the day to trigger meaningful vitamin D production, even on clear days. People with darker skin tones require significantly more sun exposure to produce the same amount of vitamin D as those with lighter skin, due to the protective effect of higher melanin levels. This makes deficiency considerably more prevalent among people from South Asian, African, and Middle Eastern backgrounds.

Clothing that covers the arms and legs, whether for cultural, religious, or personal reasons, also reduces skin exposure. And as we age, the skin becomes less efficient at producing vitamin D from sunlight, so older adults are at greater risk regardless of how much time they spend outdoors.

Who Is Most at Risk

While anyone can be deficient, certain groups are at higher risk and worth knowing about:

• People with darker skin tones
• Older adults
• Pregnant and breastfeeding women
• Breastfed infants, particularly if the mother is deficient
• People who spend most of their time indoors
• Those who cover most of their skin outdoors
• People who are obese, as vitamin D is fat-soluble and can be sequestered in fatty tissue
• People with conditions affecting fat absorption, such as coeliac disease or Crohn's disease

If you fall into one or more of these categories, it is worth discussing testing with your GP, even if you feel well.

What Are the Symptoms

This is where vitamin D deficiency can be deceptive. Many people with low levels have no symptoms at all. When symptoms do occur, they are often nonspecific and easy to attribute to other causes.

Fatigue is the most commonly reported symptom. People describe feeling tired despite adequate sleep, or having difficulty sustaining energy through the day. Muscle weakness or achiness, particularly in the legs, is another. Some people notice bone pain, most commonly in the lower back, hips, or legs. Low mood or a general feeling of flatness can also be associated, though the relationship between vitamin D and mood is complex and not fully understood.

In children, severe deficiency can cause rickets, characterised by bowed legs, soft bones, delayed walking, and dental problems. This is now rare in Australia but does still occur, particularly in children who are breastfed without supplementation and have limited sun exposure.

How Is It Diagnosed

A simple blood test measuring 25-hydroxyvitamin D gives a clear picture of your vitamin D status. Results are generally interpreted as follows: levels below 50 nmol/L are considered deficient, 50 to 75 nmol/L is considered insufficient, and above 75 nmol/L is generally considered adequate for bone health. Some guidelines suggest higher targets for certain populations, such as older adults.

Medicare covers the cost of this test in specific circumstances, including when there are clinical signs or symptoms of deficiency, or when a person belongs to a high-risk group. Your GP can advise whether you meet the criteria for a bulk-billed test.

Treatment and How to Maintain Good Levels

For most people, supplementation is the most practical and safe approach to correcting deficiency. Over-the-counter vitamin D supplements are widely available and inexpensive. For people who are significantly deficient, a GP may recommend a higher loading dose initially, followed by a maintenance dose. The appropriate amount varies depending on how low your levels are and other individual factors, so it is worth getting personalised advice rather than self-prescribing large doses.

Some sun exposure does contribute to vitamin D production, and a small amount of unprotected exposure outside peak UV hours can help, particularly in summer. Cancer Council Australia advises that a few minutes of sun exposure to the face, arms, and hands on most days is sufficient in summer for most fair-skinned people. In winter, particularly in southern Australia, longer exposure may be needed and supplementation is often more reliable.

Dietary sources of vitamin D are limited but include oily fish such as salmon, sardines, and mackerel, as well as eggs and fortified foods. Diet alone is generally insufficient to correct deficiency but can contribute to maintaining adequate levels.

A Note on Over-Supplementation

It is worth mentioning that vitamin D toxicity, while uncommon, is possible. Very high doses taken over time can cause calcium to accumulate in the blood, leading to nausea, weakness, kidney problems, and other complications. This is why testing before starting high-dose supplementation is sensible, and why following medical guidance matters. Standard over-the-counter doses are generally safe, but avoid taking very high doses without medical supervision.

When to Come In

If you have been feeling persistently fatigued, notice muscle aches or bone pain, or fall into one of the higher-risk groups mentioned above, it is worth booking an appointment to discuss a vitamin D test. It is a quick and straightforward blood test, and if deficiency is found, it is very treatable. Getting on top of it early is much better than addressing the consequences of prolonged deficiency down the track.