Calcium
Everyone knows calcium builds bones. But most people don't know that supplementing too much can be harmful. Here's how to get the right amount — without overdoing it.
Calcium is essential for bone density, muscle function, and nerve signalling. But here's the nuance most guides miss: getting too much from supplements (above 1000 mg/day) may increase cardiovascular risk. The best approach is to get as much as possible from food (dairy, greens, ragi) and only supplement the gap — always paired with vitamin D and K2.
Good for you if: You don't eat much dairy, are post-menopausal, have been told you're at risk for osteoporosis, or have confirmed low calcium intake.
Dive deeper into the researchCommon side effects
- Constipation (common with calcium carbonate)
- Excess supplementation linked to cardiovascular risk
- Always pair with vitamin D3 and K2 for proper utilisation
What does calcium do?
About 99% of your body's calcium is stored in your bones and teeth. The remaining 1% circulates in your blood and is critical for muscle contraction, nerve transmission, blood clotting, and enzyme function. Your body will actually steal calcium from your bones to maintain blood levels — which is why chronic low intake leads to bone loss.
The key insight: calcium alone isn't enough. Without vitamin D (to absorb it) and vitamin K2 (to direct it to bones instead of arteries), calcium can end up in the wrong places — contributing to arterial calcification rather than bone strength.
What can you expect?
- Maintained bone density — especially important for post-menopausal women
- Fewer fractures — when combined with vitamin D and K2
- Better muscle function — calcium is essential for contraction
- Reduced PMS symptoms — studies show 1000–1200 mg/day improves PMS
How to take it
Aim for 1000–1200 mg total daily calcium (food + supplements). Calculate how much you get from food first. Only supplement the gap — usually 500 mg is enough for most people. Split doses (250 mg twice daily) for better absorption.
Always take with vitamin D3 (1000–2000 IU) and vitamin K2 MK-7 (100 μg) to ensure proper utilisation.
Food sources in India: Milk (300 mg/cup), curd (275 mg/cup), paneer, ragi (finger millet — 344 mg/100 g), sesame seeds, amaranth, and dark leafy greens.
Which form to buy?
| Form | Notes |
|---|---|
| Calcium citrate | Better absorbed; can take on empty stomach; less constipation |
| Calcium carbonate | Cheaper; take with food; can cause constipation |
| Calcium + D3 + K2 combo | Ideal; ensures proper utilisation |
Available from Shelcal, Calcimax, and generic brands at ₹150–400. If you choose to supplement, calcium citrate is generally better tolerated.
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eterni tracks your vitamin D, calcium, and bone-related markers — connecting supplements to outcomes.
Get early accessFrequently Asked Questions
Should I take calcium supplements or just eat more dairy?
Food first, always. Calcium from food (dairy, ragi, leafy greens, sesame) is better absorbed and safer than supplements. Only supplement if your total dietary intake falls below 800–1000 mg/day. Over-supplementing is linked to cardiovascular risk.
Why do I need vitamin K2 with calcium?
Vitamin K2 activates a protein called osteocalcin that directs calcium into your bones and teeth. Without K2, calcium can deposit in your arteries instead. The combination of calcium + D3 + K2 ensures calcium goes where you want it.
Can too much calcium be harmful?
Yes. Studies suggest that calcium supplementation above 1000–1200 mg/day (from supplements alone) may increase the risk of cardiovascular events and kidney stones. Get most of your calcium from food and only supplement the shortfall.
Is ragi (finger millet) really that high in calcium?
Yes — ragi contains about 344 mg of calcium per 100 g, making it one of the richest non-dairy calcium sources available in India. A single ragi roti or bowl of ragi porridge can provide 200+ mg of calcium.
How it works in your body
Calcium absorption occurs primarily in the small intestine via two pathways: active transport (regulated by vitamin D) and passive diffusion (concentration-dependent). Vitamin D stimulates the production of calbindin, a calcium-binding protein that facilitates intestinal absorption. Without adequate vitamin D, you absorb only 10–15% of dietary calcium instead of 30–40%.
Vitamin K2 activates matrix Gla protein (MGP) in blood vessels (preventing calcium deposits) and osteocalcin in bones (attracting calcium for mineralisation). This is why the trio of calcium + D3 + K2 is more effective — and safer — than calcium alone.
What the studies show
- Bone density: Calcium + vitamin D reduces fracture risk by 15–30% in post-menopausal women
- Cardiovascular risk: Calcium supplements alone (without K2) associated with increased MI risk in some meta-analyses
- PMS: 1000–1200 mg/day of calcium reduced PMS symptoms by 48% in a large RCT
- K2 protection: Adding K2 to calcium + D3 improved bone density while protecting arteries
Side effects & safety
- Constipation — Common with calcium carbonate. Switch to calcium citrate if this happens.
- Kidney stones — Excess supplemental calcium may increase stone risk. Dietary calcium actually reduces risk.
- Cardiovascular concerns — Over-supplementation without K2 may contribute to arterial calcification. Stay within 500–600 mg supplemental and always pair with K2.
- Drug interactions — Calcium can interfere with absorption of thyroid medication, tetracycline antibiotics, and bisphosphonates. Space them 2–4 hours apart.
Which labs to check
- Serum calcium — usually normal even in deficiency (bones buffer it)
- Vitamin D (25-OH) — essential partner; aim for 40–60 ng/mL
- DEXA scan — gold standard for bone density, especially post-menopause
- PTH — elevated parathyroid hormone suggests calcium or vitamin D insufficiency
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