Nutrient Spotlight: Calcium

Written by: Nicole, The Fast 800 Health Coach

We’re often told as youngsters to drink our milk for strong bones, and this is, of course, true. What can come as a surprise is just how many varied sources of calcium are available in our diet, and how complex and intricate the balance of calcium in the body really is.

While they might seem like solid, immovable structures, our bones are changing and remodelling every day of our lives, to ensure calcium can get to all the places we need it to go. Calcium is essential not just for bone structure and strength, but also plays a crucial role in other processes that keep us alive.

What is calcium?

Calcium is the most abundant mineral found in the human body. The majority of our calcium is stored in bones and teeth. Calcium crystals, called hydroxyapatite, form amongst the collagen fibres of bone matrix, creating a dense and strong connective tissue to support a growing and moving body.¹

There is also a very small amount of calcium circulating in the blood at all times. This circulating calcium is tightly regulated through homeostasis, influenced and controlled through hormones and vitamin D via the thyroid, parathyroid, intestines, bones, and kidneys.

The homeostasis of blood levels of calcium is so important that the bones release their calcium in order to maintain it, no matter the state of bone mineral density. For this reason, conditions of low bone density (such as osteopenia and osteoporosis) are often symptomless until discovered through routine testing or broken bones.

Why do I need calcium?

The calcium we store in our bones and teeth provides a framework for the body. By providing attachment points for the muscles, the bones become levers that allow us to sit, stand, and move freely. As we grow, we need more calcium for our bones to increase in size and strength, supporting the body in development from birth to crawling and walking.

We also need calcium circulating through the bloodstream. Its presence acts as a messenger, signalling the need for different functions depending on where it is detected. Calcium is essential for cardiovascular health by maintaining normal blood pressure and blood clotting. It also plays a role in regulating muscle contractions (including the heart muscles), transmitting nerve impulses, the secretion of certain hormones, and the activation of some enzyme reactions.

These functions are very tightly regulated, which means the level of blood calcium is constantly being maintained through exchange with the bones.

How much calcium do I need?

The daily intake of calcium needed depends on age, whether pregnant or breastfeeding, and in some cases, certain medical conditions. There are also slightly different guidelines in each country. For personalised recommendations, please speak to your regular healthcare provider.

To keep things general, below are the daily intake recommendations as an average of the Australian, UK, and USA dietary guidelines for adults (general population).^{2 3 4}

Women      Average
19-30 yr      900 mg/day
31-50 yr      900 mg/day
51-70 yr      1235 mg/day
>70 yr         1235 mg/day

Men           Average
19-30 yr     900 mg/day
31-50 yr     900 mg/day
51-70 yr     1065 mg/day
>70 yr        1235 mg/day

How can I make sure I get enough?

For most healthy adults, adequate calcium intake is easily achieved through the diet. While supplementation can be helpful and is necessary for some, we absorb calcium through food more efficiently.⁴

Below we have included a list of foods that regularly appear in The Fast 800 programme recipes with their approximate/average calcium content (per 100g).

Absorption

There are a number of other factors to consider when getting enough calcium. While quantity is most important, absorption is also key. Stomach acid is the first step, helping to keep calcium soluble so it can later be absorbed in the intestines. In addition to this, certain nutrients enhance the absorption of calcium, while others can impede it.

Vitamin D plays an integral role in calcium absorption; the two go hand in hand. Without adequate Vitamin D, the body is not able to absorb enough calcium from the diet, even when calcium intake is high. This can lead to more calcium being released from the bones to ensure blood calcium remains stable. Conversely, with adequate vitamin D, calcium absorption efficiency can increase, so that even if calcium intake is lower than needed, the body can absorb more of the available calcium to achieve homeostasis.⁵

Some plant-based sources of calcium also contain nutrients that reduce the bioavailability of their calcium. These include phytates, found in such foods as nuts, seeds, and grains, and oxalates, found in spinach, silverbeet (chard), and beans.² This means it is important to include a wide variety of different calcium sources in your diet to ensure adequate intake and absorption, and not to totally exclude these foods, as they provide other important nutrients.

Sources of Calcium (milligrams per 100g)

Dairy
Parmesan 970mg
Cheddar 763mg
Mozzarella 685mg
Halloumi 620mg
Feta 323mg
Ricotta 232mg
Full fat Greek yoghurt 185mg
Full fat cow’s milk 104mg
Cottage cheese 89mg
Cream cheese 69mg
Whipping/heavy cream 60mg
Sour cream 50mg
Butter 17mg

Other animal-based
Pecorino 743mg
Sardines 381mg
Sheep’s milk 180g
Anchovies 167mg
Oysters 134mg
Goat’s milk 110mg
Goat’s cheese 63mg
Eggs 47mg
White fish 33mg
Tinned tuna 12mg
Chicken (breast) 12mg
Fresh salmon 7mg
Pork (fully-trimmed & diced, unspecified cut) 6mg
Beef (fully-trimmed & diced, unspecified cut) 5mg
Lamb (fully-trimmed & diced, unspecified cut) 5mg

Plant-based
Almonds 250mg
Brazil nuts 150mg
Pistachios 90mg
Walnuts 89mg
Hazelnuts 86mg
Cashews 34mg

Chia seeds 631mg
Flaxseeds 255mg
Sunflower seeds 100mg
Sesame seeds 62mg
Pumpkin seeds 43mg

Cocoa/cacao 150mg

Bread (wholemeal sourdough) 80mg
Quinoa 47mg
Whole rolled oats 38mg
Buckwheat 17mg
Brown rice 11mg

Lentils, dried red 22mg

Tofu 320mg
Soy beans, cooked 76mg
Black beans, cooked 57mg
Cannellini beans, cooked 46mg
Chickpeas, cooked 45mg
Kidney beans, cooked 36mg
Lentils, green or brown 21mg

Pak choy/bok choy 83mg
Spinach 53mg
Broccoli 32mg
Celery 44mg
Kale 35mg
Carrots 30mg
Sweet potato 27mg
Eggplant 23mg
Zucchini 18mg
Cucumber 18mg
Butternut 18mg
Cauliflower 17mg
Avocado 13mg
Asparagus 11mg
Tomato 9mg
Capsicum, green 8mg (red 4mg)

Blackberries 30mg
Oranges 29mg
Raspberries 26mg
Strawberries 18mg
Pears 7mg
Apples 5mg
Bananas 5mg
Blueberries 4mg

Oat milk (fortified) 124mg
Soy milk 115mg
Almond milk 67mg

Calcium is more than just bone scaffolding – it’s the body’s most abundant mineral and an essential player in everything from nerve signals to muscle contractions. While the majority is locked away for strength, your bones constantly release calcium to keep vital systems running through tight homeostasis.

To support this critical balance, prioritise a diverse diet rich in both animal and plant sources, and remember the golden rule of absorption: Calcium and Vitamin D are inseparable partners. By fueling your body with these two nutrients, you ensure total support for your health, from structure to function.