Calcium

Calcium is the most abundant mineral in the body. About 99 percent of it is stored in bones and teeth, where it provides structural density and strength. The remaining one percent circulates in the blood and soft tissue, where it’s involved in muscle contraction, nerve signaling, and blood clotting. That one percent sounds small but the body guards it carefully — if blood calcium drops, it pulls calcium from bone to compensate. That process works fine in the short term. Over years, consistently low dietary calcium intake means the body is quietly drawing down its own skeletal reserves to maintain normal function.

Bone density isn’t a concern that announces itself early. It builds or erodes slowly over decades, which is why calcium intake in younger years matters more than most people realize. Peak bone mass is largely established by the mid-twenties. What you do after that is maintenance. The earlier adequate calcium intake becomes a habit, the better the foundation you’re working from later in life.

Dairy is the most concentrated and well-absorbed dietary source, which is why people who don’t consume dairy need to be more intentional about calcium than those who do. Leafy greens like kale and bok choy provide meaningful calcium in a form that absorbs reasonably well. Sardines and canned salmon with bones are excellent non-dairy animal sources. Fortified plant milks are a practical option for people avoiding dairy entirely.

Calcium doesn’t work in isolation. Vitamin D is required for calcium absorption in the gut — without adequate vitamin D, you can be eating plenty of calcium and still not absorbing it properly. Vitamin K2 helps direct absorbed calcium to bone rather than soft tissue. Magnesium is involved in calcium metabolism. It’s less a single nutrient story and more a system.

Reference Card

Mineral type: Major mineral Pillar: Nourish

What it does for you

Builds and maintains bone density and tooth strength
Enables muscle contraction — including the heart
Supports nerve signaling
Involved in blood clotting

Where to get it

Dairy — milk, yogurt, cheese
Fish with bones — sardines, canned salmon
Leafy greens — kale, bok choy, collard greens, broccoli
Fortified plant milks and some fortified cereals
Tofu made with calcium sulfate

Considerations

Vitamin D is required for calcium absorption — adequate vitamin D status matters as much as calcium intake
Vitamin K2 helps direct calcium to bone rather than soft tissue
The body pulls calcium from bone when dietary intake is consistently low — a process that works short term but erodes bone density over time
Absorption is better in smaller doses throughout the day than in one large amount

Signs your intake might be low

Muscle cramps or spasms
Brittle nails
Bone density loss over time — often silent until a fracture or scan reveals it

Common myths

Dairy is the only reliable calcium source — leafy greens, canned fish with bones, and fortified plant milks all provide meaningful calcium for people who don’t consume dairy
Taking a calcium supplement covers bone health — bone health involves vitamin D, vitamin K2, magnesium, and physical loading through resistance training alongside calcium; supplements alone don’t replicate what a varied diet and active lifestyle provide