Calcium and vitamin D are two of the most talked-about nutrients when it comes to bone health. They're also two of the most misunderstood. Some patients I see rely on calcium tablets without ever thinking about food sources. Others assume they're getting enough vitamin D from daily life, but have never checked their level. The reality is that neither supplements nor sunshine alone tell the full story.
The evidence on what actually works has shifted over the last decade. Some of the advice that was standard ten years ago has been updated, and some widely held beliefs about supplements have been challenged. This guide covers what the current Australian guidelines recommend, what the research supports, and how to apply it in practice.
How much calcium do you actually need?
Calcium is the main structural mineral in bone. Your body doesn't make it, so it has to come from what you eat. If you're not getting enough from food, your body draws calcium from your skeleton to maintain the blood calcium level it needs for essential functions like muscle contraction and nerve signalling. Over time, that withdrawal weakens the bones.
The Australian recommended daily intake depends on your age and sex.
| Group | Calcium (mg/day) |
|---|---|
| Men 19 to 70 | 1,000 |
| Men 71+ | 1,300 |
| Women 19 to 50 | 1,000 |
| Women 51+ | 1,300 |
| Upper limit (all adults) | 2,500 |
The best way to reach these targets is through food. Dairy products are the most calcium-dense food group per serve, but they're not the only option. Canned fish with bones, calcium-set tofu, and fortified plant milks are all meaningful sources. If you're dairy-free, it's still possible to meet your requirements with careful planning.
Best food sources of calcium
| Food | Serve | Calcium |
|---|---|---|
| Canned sardines | 100g | ~380mg |
| Firm tofu (calcium-set) | 100g | ~350mg |
| Yoghurt | 200g tub | ~340mg |
| Milk (full or reduced fat) | 250mL glass | ~300mg |
| Hard cheese (e.g. cheddar) | 40g slice | ~300mg |
| Fortified plant milk | 250mL glass | ~300mg |
| Canned salmon | 100g | ~220mg |
| Bok choy | 1 cup cooked | ~160mg |
| Kale | 1 cup cooked | ~100mg |
| Almonds | 30g (small handful) | ~75mg |
Absorption matters
Not all calcium is absorbed equally. Dairy calcium is well absorbed (about 30%). Some plant sources are excellent: kale has roughly 50% absorption. Others are poor: spinach, despite its calcium content, has only about 5% absorption due to its high oxalate content. The numbers in the table above are the total calcium per serve, not the amount your body absorbs.
Your body can only absorb about 500mg of calcium at a time. Eating all your calcium in one meal means the excess passes through unabsorbed. Spreading your intake across two or three meals is more effective.
If you're using fortified plant milk, shake the carton well before pouring. The added calcium settles to the bottom, and you may not be getting the full amount listed on the label if you skip this step.
Vitamin D: the nutrient you can't eat enough of
Vitamin D is essential for calcium absorption. Without adequate vitamin D, your body absorbs only 10 to 15% of the calcium you eat. With healthy vitamin D levels, that figure rises to 30 to 40%. You could be eating the right amount of calcium and still not benefiting from it if your vitamin D is low.
The target blood level recommended in Australia is at least 50 nmol/L, measured at the end of winter (when levels are at their lowest). Some experts advocate for 75 nmol/L, but the current RACGP and Healthy Bones Australia guideline uses 50 nmol/L as the threshold.
The challenge is that food alone rarely provides enough. The richest dietary sources are oily fish and UV-exposed mushrooms, but even with deliberate effort, most people can't meet their vitamin D requirement from food.
| Food | Serve | Vitamin D |
|---|---|---|
| Oily fish (salmon, sardines, mackerel) | 100g | ~400 to 600 IU |
| Mushrooms, UV-exposed (vitamin D mushrooms) | 100g | ~400 IU (variable) |
| Cod liver oil | 1 teaspoon | ~400 IU |
| Eggs (whole) | 1 large | ~40 IU |
| Fortified milk | 250mL | ~40 to 80 IU |
| Fortified margarine | 1 tablespoon | ~40 IU |
Sunlight is the primary source of vitamin D for most Australians. When UV light hits your skin, it triggers the synthesis of vitamin D. The amount of time you need depends on the season, your skin colour, and where you live.
Sunshine and vitamin D in Adelaide: a seasonal picture
Adelaide sits at 34.9 degrees south. That latitude means there's a significant seasonal difference in UV exposure, and it has a direct impact on your ability to make vitamin D.
In summer, most people get enough vitamin D through everyday activities. In winter, the UV index in Adelaide stays below 3 for most of the day, which means your skin produces very little vitamin D even with direct exposure. This is sometimes called the "vitamin D winter."
The table below shows the approximate peak UV index in Adelaide by month. These are averages and will vary day to day. They give a general sense of how the seasons affect vitamin D production, but they're not a substitute for checking your level with a blood test if you have risk factors for deficiency.
Sun protection should always be your default when the UV index is 3 or above. Sunscreen, hats, and protective clothing reduce your skin cancer risk. They also reduce vitamin D synthesis, but during the warmer months (September to April), the UV is strong enough that most people still produce adequate vitamin D from brief incidental exposure, even with sun protection in place.
In Adelaide from May to August, UV levels are too low for reliable vitamin D synthesis without deliberate midday exposure. During these months, a daily vitamin D supplement (1,000 to 2,000 IU) is often the most practical approach, particularly for people who spend most of their time indoors, have darker skin, or are older. Your GP can check your level and advise on what makes sense for you.
This guide is not a recommendation to reduce your sun protection. The Cancer Council's position is clear: protect your skin when the UV index is 3 or above. If you're concerned about vitamin D, talk to your GP about testing and supplementation rather than reducing sunscreen use.
Older adults produce vitamin D less efficiently because the skin thins with age, reducing the amount of the precursor chemical (7-dehydrocholesterol) available. People who work indoors, wear covering clothing for cultural or religious reasons, or use sunscreen consistently year-round may also be at higher risk of deficiency, even in summer.
Your GP can check your vitamin D level with a simple blood test. Testing is recommended for people with osteoporosis, a history of fracture, or specific risk factors for deficiency. It's not recommended as a routine screen for everyone.
Do you need supplements?
This is the question I get most often, and the answer is more nuanced than many people expect.
Calcium supplements
The current Australian guideline takes a food-first approach. The evidence suggests that calcium supplements on their own have modest-to-no benefit for reducing fracture risk in healthy, community-dwelling adults who are already getting adequate calcium from their diet.
Where supplements do have a role is when dietary intake consistently falls short. If you're not reaching your recommended daily amount through food (and many Australians aren't), a supplement can fill the gap. The goal is to reach your target total intake, not exceed it.
Practical tip
If you do take a calcium supplement, take it in smaller doses (500mg or less at a time), because that's all your body can absorb in one sitting. Calcium citrate can be taken with or without food. Calcium carbonate is better absorbed with meals.
The cardiovascular question
You may have seen reports suggesting calcium supplements could increase heart attack risk. This has been debated in the medical literature for over a decade, and the evidence is genuinely mixed. Some analyses have suggested a small increase in cardiovascular events with supplemental calcium, while a more recent review of over 55,000 participants found no significant excess risk.
The most practical position, and the one the 2024 RACGP/Healthy Bones Australia guideline supports, is that dietary calcium is preferred because it comes packaged with other nutrients and doesn't carry the same theoretical concern. Supplements are appropriate when dietary intake falls short, but the goal is to make up the difference, not to maximise intake. The NHMRC lists 2,500mg per day as the upper level of intake from all sources, but this is a ceiling rather than a target. For people with existing cardiovascular risk factors, there is no proven benefit to pushing calcium intake toward this limit, and your GP can help you work out the right balance for your individual situation.
Vitamin D supplements
If your blood level is below 50 nmol/L, supplementation is recommended. The preferred dose is 1,000 to 2,000 IU daily. Daily dosing produces more stable blood levels than weekly or monthly large doses.
Monthly high-dose vitamin D (such as 50,000 IU once a month) does not appear to reduce fracture risk. In one study, a single annual megadose of 500,000 IU actually increased falls and fractures. The 2024 guideline explicitly recommends daily or weekly dosing over monthly bolus.
Vitamin D toxicity is rare but possible at sustained intake above 4,000 IU per day. It can cause high blood calcium levels, kidney stones, and other complications. For most people, 1,000 to 2,000 IU daily during the winter months is appropriate. Your GP can advise on the right dose for your situation.
Combined calcium and vitamin D
The strongest evidence for supplementation comes from combining the two. A pooled analysis of six randomised trials found that combined calcium and vitamin D reduced hip fracture risk by approximately 16%. The benefit was most pronounced in people who were deficient (particularly those in residential aged care or who were frail and housebound).
For healthy, active, community-dwelling older adults who are getting adequate calcium and vitamin D from food and sun, the added benefit of supplementation is much smaller. That's why the guideline focuses on identifying and correcting deficiency rather than blanket supplementation for everyone.
Common misconceptions
"I take calcium tablets, so I'm covered."
Calcium supplements alone have not been shown to significantly reduce fracture risk in healthy community-dwelling adults. Exercise, falls prevention, and osteoporosis medication (if indicated) are all more important interventions. Supplements are a safety net for dietary shortfall, not a standalone solution.
"I get plenty of sun, so I don't need to think about vitamin D."
In Adelaide from May to August, UV levels are too low for reliable vitamin D synthesis without deliberate midday exposure. Older adults produce vitamin D less efficiently even with the same sun exposure. And people who work indoors, cover their skin, or apply sunscreen year-round may be deficient even in summer. A blood test is the only way to know your level.
"Dairy is the only way to get enough calcium."
Dairy is the most calcium-dense food group per serve, and it is well absorbed. But adequate calcium can be achieved on a dairy-free diet with careful planning. Calcium-set tofu, canned fish with bones, fortified plant milks (shake well), bok choy, and kale are all useful sources. The key is knowing which foods provide meaningful amounts and including them consistently.
Weight-bearing exercise does more for your bones than supplements.
Resistance training and impact exercise are the strongest modifiable stimuli for maintaining and building bone density. Calcium and vitamin D are necessary foundations, but they don't replace the effect of loading the skeleton through exercise. The combination of adequate nutrition and the right kind of exercise is more effective than either alone.
When to talk to your GP
Consider asking about calcium and vitamin D if any of the following apply to you.
- You've been diagnosed with osteoporosis or osteopenia
- You've had a fracture from a minor fall or bump
- You avoid dairy or follow a restricted diet
- You spend most of your time indoors or cover your skin
- You're a woman over 50 or a man over 70
- You're on osteoporosis medication (adequate calcium and vitamin D are needed for the medication to work properly)
- You're taking corticosteroids long-term
- You live in Adelaide and haven't checked your vitamin D level, particularly heading into winter
Your GP can check your vitamin D level with a blood test, estimate your dietary calcium intake, and advise whether supplementation is appropriate for your individual situation. For most people, the answer involves a combination of dietary adjustment, sensible sun exposure, and targeted supplementation where there's a genuine gap.
Calcium and vitamin D are foundations, not cures. They're necessary for bone health, but they work best alongside weight-bearing exercise, falls prevention, and medical treatment if it's needed. Getting the foundations right is a practical step you can take now, and it's one of the most straightforward conversations to have with your GP.
Wondering if you're getting
enough for your bones?
Book an appointment and we can check your vitamin D, review your dietary calcium, and work out a practical plan.
Common questions about calcium and vitamin D
Clinical information in this article is informed by the 2024 RACGP/Healthy Bones Australia guideline for osteoporosis management and fracture prevention, NHMRC nutrient reference values, Cancer Council Australia UV and vitamin D recommendations, and published research including Yao et al. 2019 (JAMA Network Open) and Bolland et al. 2015 (BMJ). This is general information only. Your GP can advise on what's relevant for your individual situation.
