Calcium (Ca)

What is calcium?

Calcium is a mineral that helps us maintain strong bones and teeth, and supports other essential processes in the body. It is the most abundant mineral in the body, and 99% of the body’s calcium is found in teeth and bones.^{1, 2} Since our bodies cannot produce calcium, we must get it through food or supplements.

Why we need it

Calcium’s major function is providing structure and rigidity to our bones and teeth. Calcium makes up a large part of hydroxyapatite, a crystal substance that forms the foundation of bones and teeth. In this way, calcium is vital for healthy bones and teeth.

The small amount of calcium that is not in bones and teeth is important for other miscellaneous functions. For instance, this calcium supports muscle activity, blood vessel function, and hormone secretion, among other functions.¹

Where it’s found

Calcium is found mainly in dairy products like milk, cheese, and yogurt. It is also found in some fish and seafood, as well as nuts, tofu, and certain vegetables like spinach, kale, and broccoli. Additionally, calcium can be added to foods like soy milk or orange juice, through a process called fortification.³ Calcium can also be taken as a supplement. It’s available as a stand-alone supplement, as well as part of a multivitamin.²

Daily requirements

The daily Recommended Dietary Allowance (RDA) for calcium, or the amount that is likely to meet the needs of most healthy people, is 700-100 milligrams (mg) for children, 1300 mg for adolescents aged 9-18 years, 1000 mg for adults aged 19-30 years and men aged 51-70 years, 1200 mg for women over the age of 51, and 1200 mg for men over the age of 70.

Calcium deficiency

When you don’t get enough calcium, your bones may become weak and more likely to break. Severe calcium deficiency may lead to bone diseases such as rickets (in children) and osteoporosis (in adults), both of which are characterized by weakening of the bones and an increased risk of fractures. Calcium deficiency has also been linked to an increased risk of kidney stones and colon cancer.³

Groups that may be at a higher risk for calcium deficiency include postmenopausal women, as well as people who do not consume dairy products.

Can you get too much calcium?

Calcium can have harmful effects if consumed in excessive amounts. Too much calcium building up in the blood can cause symptoms like fatigue, heart arrhythmias, weight loss, and kidney stones.¹ This is almost always due to excessive calcium supplementation, rather than eating too much calcium from foods.¹

To prevent toxicity, a Tolerable Upper Intake Level (UL) has been established for calcium. The UL is 1000-1500 mg for infants, 2500 mg for children, and 2500-3000 mg for adolescents and adults.¹

Fun facts

Some plant-based foods (e.g., spinach, collard greens, and beans) contain compounds like oxalates and phytates, which can interfere with calcium absorption in the body.¹ Thus, while these foods contain calcium, we might absorb only a small portion of it.

Vitamin D, which we get through food and sunlight, helps keep our calcium levels in a safe range. For example, vitamin D allows us to absorb calcium from food, and it adjusts how much calcium is excreted by the kidneys or released from the bones, which is important when calcium consumption is low.¹