Calcium: Benefits, Immune Support and How Much You Need

Calcium is the most abundant mineral in your body, and it's best known for building strong bones and teeth [1]. But it does a lot more than that. Calcium helps your muscles move, your nerves send messages and your body release hormones [1]. It also works as a team with vitamin D and magnesium, which is why research-based formulations combine all three [1] [2].

What is calcium?

Calcium is a mineral your body needs to build and maintain strong bones and to carry out many other important jobs [1]. About 98% of the calcium in your body is stored in your bones, and almost all the rest is in your teeth [1].

Here's something many people don't realize: your bones aren't just a frame. They're also your body's calcium bank. Bone is constantly being broken down and rebuilt, and your body draws on that bank to keep the calcium in your blood at a steady level [1].

To absorb calcium from the foods we eat, your body needs vitamin D [1]. Your body also absorbs calcium more efficiently in smaller amounts. It takes in about 45% of calcium at intakes of 200 mg a day, but only about 15% at intakes above 2,000 mg [1].

What does calcium do for the body?

Calcium's best-known job is giving your bones and teeth their structure and hardness [1].

Calcium is important to five things inside the human body: the bones and teeth, the muscles, the nerves, the blood vessels and hormones, and the immune system. Let's take each one individually.

• The bones and teeth: Calcium gives them their structure and strength [1].
• The muscles: Your muscles need calcium to move [1].
• The nerves: Calcium helps your nerves carry messages between your brain and every part of your body [1].
• The blood vessels and hormones: Calcium helps your blood vessels move blood through your body, and it helps release hormones that affect many of your body's functions [1].
• The immune system: And the last one. Inside your immune cells, calcium acts as a signal that switches them on when a threat shows up [3] [4].

Why is calcium important for the human body?

Without enough calcium over time, your bones can become weak and fragile. That can lead to osteoporosis, which raises the risk of falls and broken bones, as well as rickets in children and osteomalacia, or soft bones, in adults [1]. After about age 30, your bones slowly start losing calcium, and in middle age that loss speeds up [1].

Remember the calcium bank? When you don't get enough from food, your body keeps your blood level steady by making withdrawals from your bones [1]. You won't feel it day to day, but over the years those withdrawals add up.

Low intake is more common than many people realize. Many Americans get less than the recommended amount, especially children and teens ages 4 to 18, people who are Black or Asian, and adults over 50 living in poverty [1]. Postmenopausal women are also at higher risk, because the body absorbs and holds on to less calcium after menopause [1].

Calcium also depends on its teammates. Without vitamin D, your body can't absorb it properly [1]. Single nutrients taken by themselves tend to give inconsistent results, which is why research-based formulations pair calcium with vitamin D3, magnesium and other nutrients [2] [5]. Calcium does its best work as part of the team, not by itself.

How does calcium support immune function?

Calcium supports immune function by acting as an on switch inside your immune cells. When a T cell, B cell or natural killer cell recognizes a threat, calcium flows into the cell and signals it to activate, multiply and release the chemical messengers that coordinate your immune response [3] [4].

Think of your immune system as having two jobs: responding strongly when a threat shows up, and calming back down once the job is done. Let's look at how calcium fits in.

• First-line (innate) defense: This is your body's rapid-response team. Calcium signals help cells such as natural killer cells and mast cells release the chemical messengers they use to sound the alarm [3].
• Targeted (adaptive) defense: This is the part of your immune system that learns and remembers specific threats. T cells and B cells need a steady flow of calcium into the cell to fully switch on, multiply and do their jobs [3] [4]. In fact, people born with rare defects in these calcium channels have serious immune problems [3].

One honest note: this calcium signaling happens inside your cells, and your body keeps the calcium in your blood within a tight range by drawing on your bones [1]. Eating extra calcium won't supercharge your immune cells. What getting enough calcium does is keep your body from having to draw down your bone reserves to supply those everyday needs.

Getting the most from calcium

If you want to get the most out of calcium, here are five things the research points to.

• Choose a form that fits you: Calcium carbonate is absorbed best when taken with food. Calcium citrate is absorbed well with or without food, and it's easier to absorb for people with low stomach acid, which is most common in older adults [1]. The Micro Daily EMF formula uses calcium citrate [6].
• Split it up: Your body absorbs calcium best in doses of 500 mg or less at a time. The NIH suggests taking smaller doses twice a day rather than all at once [1]. That lines up neatly with the twice-a-day approach of comprehensive formulas [7] [8].
• Know what your supplement covers: Micro Daily EMF provides 250 mg of calcium a day, 20% of the Daily Value [6]. That means most of your daily calcium still needs to come from food.
• Eat calcium-rich foods: Dairy foods are the top sources for most people. Canned sardines and salmon with bones, kale, broccoli, bok choy and calcium-fortified foods help, too [1]. Spinach is a surprise exception: its natural compounds block absorption, so you absorb only about 5% of its calcium, compared with about 27% from milk [1].
• Mind the timing with medications and iron: Calcium supplements can interfere with some medications, including thyroid hormone and certain antibiotics, so they're usually taken a few hours apart [1]. Calcium can also lower how much iron you absorb, as we explain on our iron page.

One last thing to keep in mind: with calcium, more isn't automatically better. Some research suggests very high calcium intakes might raise the risk of heart disease and prostate cancer, although experts overall believe calcium doesn't affect heart disease risk [1]. Staying close to your recommended amount is the safest approach.

Frequently asked questions about calcium

How much calcium do I need each day?

Most adults ages 19 to 50 need 1,000 mg a day. Men stay at 1,000 mg through age 70, while women 51 and older need 1,200 mg, and everyone over 70 needs 1,200 mg. Children and teens ages 9 to 18 need the most, 1,300 mg, because their bones are still growing [1]. The upper limit from all sources is 2,500 mg a day for adults 19 to 50 and 2,000 mg for adults 51 and older [1].

What foods are high in calcium?

Eight ounces of plain low-fat yogurt has about 415 mg, a cup of calcium-fortified orange juice about 349 mg, and half a cup of firm tofu made with calcium sulfate about 253 mg. Three ounces of canned pink salmon with the bones has about 181 mg, and a cup of low-fat cottage cheese about 138 mg [1]. Kale, broccoli and bok choy add smaller amounts that your body absorbs well [1].

Which is better, calcium citrate or calcium carbonate?

It depends on you. Calcium carbonate is absorbed best with food. Calcium citrate is absorbed well with or without food, and it's the easier choice for people with low stomach acid, which is common in older adults [1].

Who is most likely to be low in calcium?

The groups most at risk are postmenopausal women and people who don't eat dairy, including people with lactose intolerance or a milk allergy and vegans. Children and teens ages 4 to 18, people who are Black or Asian, and adults over 50 living in poverty are also more likely to fall short [1].

What happens if you don't get enough calcium?

Over time, low calcium can lead to weak, fragile bones. In adults, that can mean osteoporosis or osteomalacia, and in children it can cause rickets, a condition that causes soft, weak bones [1].

Can you take too much calcium?

Yes. Calcium supplements can cause gas, bloating and constipation in some people, and spreading out doses or taking them with meals can help [1]. Very high intakes may carry other risks, so it's best to stay below the upper limit. High blood calcium is usually caused by a health condition rather than by diet [1].

Explore more micronutrients

Calcium works alongside other nutrients. Vitamin D helps you absorb it, and magnesium works with both to keep your bones strong. Learn more about iron, vitamin B12, zinc, potassium and folate.

Key sources: NIH Office of Dietary Supplements, Calcium Fact Sheets for Health Professionals and Consumers [1]; Vaeth M, Kahlfuss S, Feske S, "CRAC Channels and Calcium Influx in T Cell-Mediated Immunity," Trends in Immunology, 2020 [4]; Prasad KN, Micronutrients in Health and Disease, CRC Press, 2019 [5]. Every numbered citation links to its full entry on our References page.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. Talk with your healthcare provider before starting any supplement, especially if you are pregnant, nursing, taking medication or have a medical condition.