There's a common assumption that living near the beach in a place like Cronulla means you're soaking up plenty of sunshine year-round. And for much of the year, that's true — warm afternoons on the esplanade, weekend swims at North Cronulla, and long summer evenings that make outdoor living a joy. But as March rolls into April and the angle of the sun begins to shift, something quietly changes. The sunlight that reaches us becomes less effective at triggering the vitamin D your body needs, and many people head into winter with levels that are lower than they realise. That's why autumn is one of the most important times of year to think about a simple blood test.
What Is Vitamin D and Why Does It Matter?
Vitamin D is often called the 'sunshine vitamin,' and for good reason — your skin produces it when exposed to ultraviolet B (UVB) radiation from sunlight. It plays a vital role in helping your body absorb calcium, which keeps your bones strong and reduces the risk of fractures and osteoporosis over time. Beyond bone health, vitamin D is involved in muscle function, immune regulation, and general wellbeing. Low levels have been associated with fatigue, low mood, and reduced immune resilience, though it's important to understand that vitamin D deficiency is just one of many possible contributors to these kinds of symptoms.
In Australia, vitamin D deficiency is more common than many people expect. Studies suggest that around one in four Australians may have inadequate vitamin D levels at some point during the year, with rates rising significantly in the cooler months. You don't have to live in Hobart to be at risk — even residents of sunny Sydney suburbs can find themselves running low by the end of winter.
Why Autumn Is the Tipping Point
The key factor isn't just how much time you spend outside — it's the angle of the sun. During summer, UVB rays hit the earth at a steep angle, particularly in the middle of the day, making vitamin D synthesis in the skin efficient and relatively quick. As autumn progresses, the sun's arc drops lower in the sky, meaning UVB rays travel through more of the atmosphere before reaching you. By the time winter arrives in Sydney, the UVB intensity between May and August can be too low for meaningful vitamin D production, particularly in the mornings and afternoons when many people are outdoors.
This means that the vitamin D stores your body built up over summer are gradually drawn down through autumn and winter. If your levels were only moderate coming out of summer — which is common for people who work indoors, use high SPF sunscreen consistently, or naturally have more melanin in their skin — you may well be deficient before spring returns. Checking your levels in autumn gives you and your GP the best opportunity to act before any depletion becomes significant.
A common myth: 'I live near the beach, so I must be getting enough vitamin D.' In reality, lifestyle factors like working indoors, sun-protective clothing, and the seasonal angle of sunlight mean coastal residents are just as vulnerable to deficiency as anyone else — especially heading into the cooler months.
Who Is Most at Risk?
While vitamin D deficiency can affect anyone, some people are at higher risk and may benefit most from autumn screening. It's worth speaking with your GP if any of the following apply to you:
- You work indoors during daylight hours and have limited outdoor time on weekdays
- You have darker skin, which requires longer sun exposure to produce the same amount of vitamin D
- You are over 70 years of age, as skin becomes less efficient at synthesising vitamin D with age
- You are pregnant or breastfeeding, as your requirements are higher
- You have a body mass index (BMI) in the obese range, as vitamin D can be sequestered in fatty tissue
- You have a condition affecting fat absorption, such as Crohn's disease or coeliac disease
- You take certain medications, including some used for epilepsy or HIV, which can affect vitamin D metabolism
- You wear full-coverage clothing for cultural or religious reasons
- You have a personal or family history of osteoporosis or fractures
Can Diet and Food Help?
Diet alone is rarely sufficient to maintain healthy vitamin D levels, but it can play a supporting role. Very few foods contain significant amounts of vitamin D naturally. The best dietary sources include:
- Oily fish such as salmon, mackerel, sardines, and tuna — particularly useful given Cronulla's fishing culture and proximity to fresh seafood
- Eggs, particularly the yolk
- Mushrooms that have been exposed to sunlight or UV light (some commercial varieties are now UV-treated)
- Fortified foods such as some brands of milk, plant-based milk alternatives, and breakfast cereals — check the label, as not all products are fortified
Including these foods regularly as part of a balanced diet is a sensible habit, but if your blood levels are already low, food sources alone are unlikely to bring them back into a healthy range. That's where testing and, where appropriate, supplementation come in.
Testing and Supplementation: What to Expect
Vitamin D status is checked through a straightforward blood test measuring 25-hydroxyvitamin D, often written as 25(OH)D. Your GP can arrange this as part of a general health check or if you have specific risk factors. In Australia, results are generally interpreted as follows: levels below 50 nmol/L are considered deficient, between 50 and 74 nmol/L may be adequate for some people but not optimal, and levels of 75 nmol/L or above are generally considered sufficient for bone and overall health. However, your GP will interpret your results in the context of your individual health history.
If your levels are low, your doctor may recommend a vitamin D supplement. These are widely available over the counter in Australia, but the appropriate dose varies significantly depending on how deficient you are. Taking very high doses without guidance isn't recommended, as vitamin D is a fat-soluble vitamin and can accumulate to excessive levels over time. Your GP can recommend the right dose for your situation and may suggest retesting in a few months to confirm your levels have responded.
Safe sun exposure still matters. While sun protection is important for skin cancer prevention, a brief period of unprotected sun exposure — typically just a few minutes in the middle of the day during summer months — is enough for most people to maintain vitamin D. Your GP can help you find the right balance for your skin type and lifestyle.
As the days shorten and that golden Cronulla afternoon light takes on its familiar autumnal softness, it's a natural moment to take stock of your health. A simple blood test is a small investment of time that can give you and your GP a clear picture of where your vitamin D levels stand — and what, if anything, needs attention before winter arrives. If it's been a while since you've had your levels checked, or if you recognise yourself in any of the risk factors above, we'd encourage you to make an appointment with one of our GPs at Cronulla Medical Practice. We're here to help you stay well through every season.