Calcium’s Role in the Body


Calcium is one of the most abundant minerals in the human body — and for good reason. Around 99% of it is stored in our bones and teeth, with the remaining 1% circulating in our blood, muscles, and tissues, playing critical roles in daily health.

Why your body needs calcium:

  • Bone and teeth strength: It’s the main structural mineral, maintaining density and resilience.

  • Muscle function: Every muscle contraction — from lifting your arm to the beating of your heart — relies on calcium.

  • Nerve communication: Calcium ions help transmit messages between your brain and body.

  • Blood clotting: It’s essential in the clotting process to stop bleeding after an injury.

  • Enzyme and hormone activity: Calcium helps trigger the release of enzymes and hormones vital for metabolism and energy.

Animal vs. Plant Calcium

Why Both Matter

Many people think of dairy as the default calcium source, but certain plant foods can also be rich in this mineral. A mix of both can give you more variety — and, in some cases, plant foods may be better tolerated for those with dairy sensitivities.

Absorption Matters

Why Not All Calcium is Equal

Calcium content on paper isn’t the whole story. How much you absorb depends on:

  • Oxalates and phytates in certain plant foods (e.g., spinach, beet greens, nuts, seeds) which bind calcium, making it less available.

  • Lactose in dairy, which may enhance absorption in those who tolerate it.

  • Processing methods — for example, calcium-set tofu has much higher levels than tofu set with other coagulants.

 

Top 7 Animal-Sourced Calcium Foods

(Calcium content per standard serving, %DRV based on 1,000 mg/day)

  1. Milk (skimmed or semi-skimmed) – 1 cup (≈240 ml) → 300 mg (30%)

  2. Yogurt (low-fat, plain) – 1 cup (≈240 ml) → 450 mg (45%)

  3. Parmesan cheese – 1 oz (≈28 g) → 335 mg (34%)

  4. Cheddar cheese – 1 oz (≈28 g) → 205 mg (21%)

  5. Mozzarella (part-skim) – 1 oz (≈28 g) → 210 mg (21%)

  6. Sardines (with bones, canned in oil) – 3 oz (≈85 g) → 325 mg (33%)

  7. Salmon (canned with bones) – 3 oz (≈85 g) → 241 mg (24%)

 

Top 7 Plant-Based Calcium Foods

(Calcium content per standard serving, %DRV based on 1,000 mg/day)

  1. Firm tofu (calcium-set) – ½ cup (≈126 g) → 430 mg (43%)

  2. Collard greens (cooked) – 1 cup → 266 mg (27%)

  3. Chia seeds – 4 tbsp (≈40 g) → 333 mg (33%)

  4. Almonds – 1 oz (≈23 nuts) → 76 mg (8%)

  5. White beans (cooked) – 1 cup → 161 mg (16%)

  6. Kale (cooked) – 1 cup → 177 mg (18%)

  7. Fortified plant milk – 1 cup (≈240 ml) → 300–350 mg (30–35%)

 
 

Maximise Calcium Uptake

tips to improve absorption

  • Pair with vitamin D — without enough vitamin D, your gut can’t absorb calcium efficiently. Aim for sun exposure, fatty fish, or supplementation if needed.

  • Spread intake throughout the day — the body absorbs calcium better in smaller doses rather than one large serving.

  • Avoid excessive caffeine and alcohol — both can increase calcium excretion.

  • Balance with magnesium and vitamin K2 — they help direct calcium into bones rather than soft tissues.

Vitamin D & Calcium

The Perfect Pair

Vitamin D acts like a “key” that unlocks calcium absorption in the gut. Without it, even a high-calcium diet can still leave you deficient.

  • Best natural sources: sunlight, salmon, mackerel, sardines, egg yolks.

  • In the UK, sunlight levels between October and April are often too low, so a supplement is commonly recommended.

 
 

Final Thoughts

Whether you’re plant-based, dairy-loving, or somewhere in between, the key is variety. Combining high-calcium foods with smart absorption strategies — plus supporting nutrients like vitamin D, magnesium, and K2 — will give your body the best chance to build strong bones, steady your nerves, and keep your muscles (including your heart) working at their best.