- Health advice
- May 14, 2015
Calcium is essential for strong bones, but less than 1 percent of the calcium in your body is actually circulating in your blood at any time. The remaining 99 percent is stored in your bones and teeth, acting as a reservoir your body draws on whenever dietary intake falls short.[1]
Why calcium matters beyond your bones
Calcium keeps your bones and teeth strong, but it also plays a role in muscle contraction, nerve signalling and blood clotting. Your body tightly regulates blood calcium levels, and when dietary intake is not enough, it draws calcium from your bones to make up the difference.[1]
Bone tissue is constantly being broken down and rebuilt throughout life. In children and teenagers this process supports growth, while for postmenopausal women in particular, breakdown can outpace rebuilding, raising the risk of osteoporosis.[2]
Healthy Bones Australia estimates that around 6.2 million Australians aged 50 and over, or roughly two in three people in that age group, are living with osteoporosis or osteopenia (low bone density), a figure projected to keep rising as the population ages.[2] Getting enough calcium is one part of managing this risk, but it works alongside several other factors covered later in this guide.
How much calcium do you need each day?
Calcium needs change across your life, rising during growth years and again after menopause or age 70. These recommended dietary intakes (RDIs) come from the National Health and Medical Research Council (NHMRC).[3]
| Age and group | Recommended daily intake |
|---|---|
| Children 1 to 3 years | 500mg |
| Children 4 to 8 years | 700mg |
| Children 9 to 11 years | 1,000mg |
| Teens 12 to 18 years | 1,300mg |
| Adults 19 to 50 years | 1,000mg |
| Women over 50 years | 1,300mg |
| Men over 70 years | 1,300mg |
Despite these recommendations, the most recent national nutrition survey found that more than half of Australians aged 2 and over do not meet their recommended calcium intake from food alone.[4] Average calcium intake among Australian adults specifically sits at around 850mg a day, below the 1,000mg baseline recommendation.[3]
Best food sources of calcium, dairy and non-dairy
Dairy foods are a well-absorbed source of calcium, but they are far from the only option if you are dairy-free for health or other reasons.
| Food | Approximate calcium |
|---|---|
| 1 cup (250ml) milk | 280mg |
| 85g sardines with bones | 200mg |
| 1 cup cooked bok choy or similar leafy greens | 150-160mg |
| ¼ cup (25g) almonds | 100mg |
| 15g tahini (sesame seed paste) | 100mg |
| 225g boiled chickpeas | 110mg |
| 1 tablespoon sesame seeds | 88mg |
| 1 medium orange | 50mg |
Gram for gram, sesame seeds, canned fish with soft bones, and leafy greens all add meaningfully to your daily calcium total, even without dairy.
What can reduce how much calcium you actually absorb
Eating calcium-rich food is only part of the picture, since not all of it is absorbed at the same rate. Naturally occurring compounds in some plant foods can bind to calcium and reduce how much your body takes up.
- Oxalic acid in spinach, rhubarb and dried beans reduces calcium absorption, so don't rely on high-oxalate vegetables as your main calcium source.
- Phytic acid in wheat bran, nuts, seeds and dried beans can also lower absorption; soaking dried beans overnight before cooking helps reduce this effect.
- Excess caffeine and salt both increase how much calcium is lost through urine, so it's worth moderating intake if you're working on your calcium levels.
A food's calcium content is not the same as how much of it your body actually absorbs. Government dietary guidance notes that, compared with milk, calcium absorption from dried beans is only around 50 percent as efficient, and from spinach around 10 percent, largely because of the oxalic acid spinach contains.[5] This is why a varied diet across several calcium sources works better than relying on any single high-oxalate food.
Nutrients that work alongside calcium
Calcium does not work in isolation. Several other nutrients support how your body absorbs and uses it for bone strength.
- Vitamin D is required for calcium to be absorbed from your gut in the first place, and Healthy Bones Australia recommends adequate vitamin D alongside calcium intake for bone health.[2]
- Magnesium is a structural part of the bone matrix and works in partnership with calcium.
- Vitamin K supports the proteins involved in bone mineralisation.
- Zinc, manganese, boron and phosphorus all play supporting roles in bone formation and structure.
Beyond calcium: other contributors to low bone density
Calcium and vitamin D are often the default focus for bone health, but they are only part of the picture. Several other factors can contribute to low bone density, including:
- Hormonal changes, including declining oestrogen after menopause or low testosterone in men
- Insufficient regular weight-bearing exercise
- Digestive conditions, such as coeliac disease, that affect nutrient absorption
- Reduced digestive enzyme production, which can affect how well nutrients are absorbed
- Family history, thyroid or kidney conditions, and certain medications, including long-term corticosteroid use
A qualified naturopath or nutritionist can help you look at these factors together, rather than treating calcium supplementation as a solution on its own.
When to see a healthcare professional
If you have risk factors for osteoporosis, such as a family history, early menopause, or a previous minimal trauma fracture, speak with your GP about a bone density (DEXA) scan rather than waiting for symptoms, since low bone density typically causes no symptoms until a fracture occurs.[2]
A sudden fracture from a minor bump or fall, ongoing bone pain, or a noticeable loss of height should also be discussed with your doctor promptly.
Building strong bones beyond diet
Diet and supplementation are only part of maintaining bone strength. Regular weight-bearing exercise, such as walking, resistance training or dancing, helps build and maintain bone density throughout adulthood.
The current Australian clinical guideline for osteoporosis management also emphasises exercise and fall-prevention strategies alongside nutrition as part of a complete approach to bone health.[6]
Can you get too much calcium?
Yes, although the risk comes almost entirely from supplements rather than food. Tolerable upper intake levels are set at 2,500mg a day for adults aged 19 to 50, dropping to 2,000mg a day for adults over 50, taking into account calcium from all sources combined.[7]
The most well-documented risk of excess calcium is kidney stones, and current research suggests this risk relates specifically to calcium supplements rather than calcium from food, since dietary calcium may actually help reduce kidney stone risk by binding to oxalate in the gut.[7] Very high intakes can also cause bloating, constipation, and in rare cases a harmful buildup of calcium in the blood, so more is not always better.
Since the risk of excess calcium is linked mainly to supplements, the safest approach is to build your calcium intake from food first, and use a supplement only to bridge the gap to your recommended daily intake, ideally with guidance from a naturopath or your GP.
The role of silica in bone health
Silica is a less well-known nutrient in the bone health conversation. Some research reviews suggest silica plays a role in bone formation and the strength of connective tissue, potentially by supporting the collagen matrix that calcium mineralises onto.[8]
The evidence for silica is less extensive than for calcium and vitamin D, so it is best considered a complementary, supporting nutrient rather than a replacement for an adequate calcium intake. Beyond bone health, silica is also associated with healthy skin, hair and nails, since it is a component of collagen throughout the body.
Frequently asked questions
How much calcium do adults need each day?
Most adults aged 19 to 50 need around 1,000mg of calcium a day. This rises to 1,300mg a day for women over 50 and men over 70, based on current NHMRC recommendations.
Can I get enough calcium without dairy?
Yes. Canned sardines with bones, leafy greens, almonds, tahini and sesame seeds are all useful non-dairy calcium sources, though a varied diet across several of these is best since absorption rates differ between foods.
What reduces calcium absorption?
Oxalic acid in foods like spinach and rhubarb, and phytic acid in bran, nuts and dried beans, can both reduce how much calcium your body actually absorbs from a meal. Excess caffeine and salt can also increase calcium loss through urine.
Is low bone density only caused by not getting enough calcium?
No. Hormonal changes, insufficient weight-bearing exercise, certain digestive conditions, and some medications can all contribute to low bone density alongside calcium and vitamin D intake.
How common is osteoporosis in Australia?
Healthy Bones Australia estimates around 6.2 million Australians aged 50 and over, or about two in three people in that age group, have osteoporosis or osteopenia (low bone density), with numbers projected to keep rising as the population ages.
Can you get too much calcium?
Yes, though the risk relates mainly to supplements rather than food. Tolerable upper intake levels sit at 2,500mg a day for adults 19 to 50 and 2,000mg a day for adults over 50, with excess supplemental calcium linked to a small increased risk of kidney stones.
What is silica's role in bone health?
Some research suggests silica supports bone formation and the collagen matrix that calcium mineralises onto, working alongside calcium rather than replacing it. The evidence base for silica is smaller than for calcium and vitamin D, so it is best viewed as a complementary nutrient.
Related articles
- Magnesium and its role in bone health
- Are you getting enough vitamin D?
- Shop our calcium and bone health range
Sources
- Better Health Channel, Victorian Department of Health. Calcium. Available from: betterhealth.vic.gov.au
- Healthy Bones Australia. About Osteoporosis, and A Burden of Disease Analysis 2023-2033. Available from: healthybonesaustralia.org.au
- National Health and Medical Research Council / Eat For Health. Nutrient Reference Values for Australia and New Zealand - Calcium. Available from: eatforhealth.gov.au
- Better Health Channel, Victorian Department of Health, citing the National Nutrition and Physical Activity Survey. Calcium. Available from: betterhealth.vic.gov.au
- Eat For Health, National Health and Medical Research Council. Nutrient Reference Values - Calcium, bioavailability. Available from: eatforhealth.gov.au
- Royal Australian College of General Practitioners and Healthy Bones Australia. 2024 guideline for osteoporosis management and fracture prevention. Medical Journal of Australia, 2025.
- National Academies of Sciences, Engineering, and Medicine / National Institutes of Health. Tolerable Upper Intake Levels for Calcium, and research on calcium supplementation and kidney stone risk.
- Jugdaohsingh R. Silicon and bone health. Journal of Nutrition, Health and Aging.
General Disclaimer
This article is intended for general informational and educational purposes only. It does not constitute medical advice and is not a substitute for professional healthcare advice, diagnosis, or treatment.
The information in this article is not intended to diagnose, treat, cure, or prevent any disease or health condition. References to health benefits reflect the current state of published research and are not claims made about any specific product. Individual results may vary.
Vitamin and mineral supplements should not replace a balanced diet. If you are pregnant, breastfeeding, taking prescription medications, or have an existing health condition, consult a qualified healthcare professional before starting a new supplement. Keep all supplements out of reach of children.
Product and collection links in this guide reflect the independent recommendation of the Mr Vitamins practitioner and retail team. No brand has paid for inclusion, placement, or editorial content.
© Mr Vitamins. All rights reserved. Content is reviewed periodically but may not reflect the most current research or regulatory guidance. Last reviewed: 23 July 2026.
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