Learn all about Calcium
What is Calcium?
Build strong bones & support muscle function with essential calcium. Also helps nerve communication & heart rhythm. Stay strong!
Benefits of Calcium
"While dairy is great for calcium, many plant foods offer it too. How well it's absorbed ('bioavailability') is key – kale calcium is better absorbed than spinach calcium. If using supplements, taking smaller doses throughout the day works better than one large dose."
- Dr. Connie Weaver, Distinguished Professor of Nutrition Science at Purdue University (source)
How to use Calcium
Dosage
Adults need 1000-1200mg daily. Best absorbed in smaller doses (500mg or less at a time).
Timing
Take with meals for better absorption. Calcium citrate form can be taken anytime; calcium carbonate form needs stomach acid (so take with food).
Notes
Vitamin D is crucial for absorbing calcium. Different supplement forms contain different amounts of actual ('elemental') calcium.
Who should take Calcium?
- Women after menopause (at higher risk of bone loss due to hormone changes)
- Older adults with decreasing bone density
- Those who eat little dairy or have conditions causing poor nutrient absorption ('malabsorption')
- Growing children and teens building bone mass
How does Calcium work?
The body tightly controls calcium levels using parathyroid hormone (PTH) and vitamin D. If blood calcium drops, PTH signals the body to activate vitamin D. Active vitamin D then increases calcium absorption from food and releases stored calcium from bones. This keeps levels steady for nerve signal transmission, muscle contraction, and enzyme function. In bones, calcium combines with phosphorus to form hard mineral crystals ('hydroxyapatite'), creating the skeleton's rigid structure.
Frequently asked questions
Natural sources of Calcium
Dairy (yoghurt, milk, cheese) is a top source and easily absorbed ('highly bioavailable'). Plant sources include kale, broccoli, bok choy, fortified plant milks, tofu made with calcium, and almonds. Sardines/salmon (with bones) also provide calcium. Absorption varies – foods high in oxalates (like spinach) contain calcium, but the body doesn't absorb it well.
Potential side effects & risks
Warnings
Check with a doctor before supplementing if you have high blood calcium ('hypercalcaemia'), kidney disease, sarcoidosis (an inflammatory condition), or a history of kidney stones. Very high intake (>2500mg daily) might increase heart/blood vessel ('cardiovascular') risk.
Side effects
Commonly causes constipation, gas, or bloating. High doses might cause kidney stones in people prone to them.
Interactions
Can reduce absorption of iron, zinc, magnesium, and certain drugs (like tetracycline/fluoroquinolone antibiotics, bisphosphonates for bone density, thyroid meds). Take calcium at least 2 hours apart from these.