Calcium 101: Bone Up on Your Knowledge

When you think about calcium, you probably think about bones — strong bones, healthy bones and, for kids, growing bones. And you’re right: From the time you’re born and well into old age, calcium does play a huge role in bone health.

But let’s give calcium all the credit it deserves. This mineral has other important roles to play within your body, too — and having too much or too little of it can really throw things out of whack.

Registered dietitian Beth Czerwony, RD, LD, explains what calcium does, how much of it you need and how to get it through your diet.

What is calcium?

Of all the many minerals in your body, calcium is the one you have the most of.

And the reason you probably associate it with bones and teeth is that most of your calcium is found in them.

“More than 99% of the calcium found in your body is in the form of teeth and bones,” Czerwony says. “The rest of it is found in your muscles and tissues and circulating through your blood.”

Even though that amount seems small, you really need that calcium in your blood. But calcium is an essential nutrient, which means that your body can’t produce it on its own. Instead, you have to get it from your diet or supplements — and if you don’t have enough of it, your body actually starts to steal it from your bones, which can cause all kinds of issues.

Why calcium is the key to healthy bones

Your body carefully self-regulates the amount of calcium in your blood. But if it senses that you’re getting low on it, it tries to make up for it by stealing some of the calcium from your bones.

“Not having adequate stores of calcium will cause the body to leach calcium from your bones in order to keep your blood levels normal,” Czerwony explains. “If your calcium levels get too low, the parathyroid hormone will signal the bones to release calcium into the bloodstream. This can cause weakening of the bones, or osteopenia.”

Low bone mineral density can ultimately lead to osteoporosis — fragile, porous bones that are at high risk for breaks.

What does calcium do for the body?

“Though calcium is most often thought about as being related to healthy bones and teeth, it also allows your body to do other critical things, like blood clotting, muscle contraction and nerve function,” Czerwony shares.

Beyond bones, here’s a little bit more about the other things calcium does for your body that make it such an important part of your diet.

Helps blood to clot

Your blood needs to be able to clot (stick together) so that you don’t bleed too much when you’re injured. When you get a scrape or a cut, calcium helps activate the platelets that stop the bleeding.

Regulates nerve function

Calcium has a huge part to play in making sure that your nerves can send messages throughout your body. It’s responsible for triggering the release of chemicals called neurotransmitters, which are the little messengers that keep your nerves in communication with one another.

Contracts muscles

There are more than 600 muscles in your body, and as you can imagine, there’s a lot of work happening behind (err, inside) the scenes to keep them all moving properly.

“Calcium plays a key role in the complex scientific process that makes sure your muscles can interact with one another and generate the right amount of force that you need for various movements,” Czerwony explains.

Keeps teeth and gums healthy

When you don’t get enough calcium, you risk not only bone loss, but also tooth decay and tooth loss. That’s because, like bones, your pearly whites need calcium in order to develop and stay strong. One study found that calcium supplements in people over 65 helped reduce the risk of losing teeth with age.

Helps regulate blood pressure

“Having adequate stores of calcium has been shown to help regulate blood pressure, specifically during pregnancy,” Czerwony notes. “This can help prevent pregnancy-related complications like hypertension and preeclampsia.”

Reduces the risk of some cancers

Studies show that getting enough calcium may help protect you from colorectal cancer, though researchers aren’t yet sure exactly how. It may also be associated with a lower risk of other cancers.

But don’t go taking calcium supplements with the hopes of reducing your risk. The National Cancer Institute says there’s not yet enough evidence that supplements can actually do that — so it’s still best to get your calcium through food.

May lower cholesterol

The jury’s still out on this one. Some studies show that getting calcium through your diet can improve cholesterol levels, while other studies show that calcium supplements don’t have any effect on cholesterol. But until scientists know for certain, don’t turn to calcium to try to lower your cholesterol.

Is calcium related to kidney stones?

If you’ve heard that too much calcium can cause kidney stones, let’s set things straight: “It’s actually calcium deficiency that is related to the formation of kidney stones,” Czerwony clarifies.

Research from two large clinical trials found that consuming a lot of calcium in your diet decreases women’s risk for kidney stones. But the same isn’t true of supplements, which can actually increase the risk of kidney stones.

The National Institute of Diabetes and Digestive and Kidney Diseases reiterates that having balanced calcium levels can help block the substances in your body that cause stones.

How much calcium do you need?

In the U.S., everyone ages 19 to 50 and ages 71 and older should get 1,000 milligrams (mg) of calcium per day.

But from ages 51 to 70, the recommended daily amount depends on your sex assigned at birth — namely because menopause, which people assigned female at birth typically experience in their early 50s, is one of the main causes of low bone density.

Here’s what the National Institutes of Health’s calcium recommendations say:

Keep in mind that these official recommendations don’t account for bodily differences like weight, height and overall health. And the amount of calcium you need changes depending on what country you live in, which dictates how calcium-rich your diet is likely to be.

“It’s always best to ask a healthcare provider how much you need,” Czerwony advises.

Too much or too little calcium

Many Americans aren’t getting enough calcium — and some may be getting too much, especially if supplements are involved.

Low calcium (hypocalcemia) can be caused by some health conditions, as well as:

• Consuming a lot of magnesium or sodium (salt).
• Drinking too much alcohol and/or caffeine.
• Eating disorders.
• Having your thyroid removed.
• Long-term use of steroids or corticosteroids.
• Vitamin D deficiency.

“It can be difficult to identify low calcium levels in your blood because you most likely won’t have symptoms until you’re experiencing a true deficiency,” Czerwony says. In fact, the signs of a calcium deficiency — like fatigue, muscle pain and tingling in your hands and feet — can be so subtle that for a while, you may not even recognize them as a problem.

On the other end of the spectrum is hypercalcemia, or having too much calcium. It can be the result of some medical conditions, but it can also happen if you take too many:

• Calcium supplements.
• Vitamin A or D supplements.
• Antacid tablets or chews (like Tums® or Rolaids®), which are made of calcium carbonate.

“If your hypercalcemia is being caused by supplements and antacids, that usually reverses soon after you stop taking them,” Czerwony notes, “but long-term hypercalcemia raises your risk of a heart attack.”

Are food sources better than supplements?

To get enough calcium, start with your diet. There are lots of calcium-rich foods to choose from, and they may already be on your regular menu.

“Dairy is your best way of getting calcium,” Czerwony confirms. Just 8 ounces of low-fat vanilla yogurt has 388 mg of calcium, while the same amount of plain, low-fat Greek yogurt has 261 mg.

Can’t do dairy? Milk-based products are the most abundant source of calcium, but they’re not the only option. Non-dairy foods like almond milk, fortified orange juice, spinach and black beans are all good sources of calcium, too.

“Tofu is particularly high in calcium if you buy the kind prepared with calcium sulfate, or gypsum,” Czerwony says. “It’s added because it helps the tofu stick together in a big block, but it also has the benefit of helping you get more calcium in your diet.”

Still, you might have trouble getting enough calcium in your diet if you don’t eat dairy.

“If you’re lactose intolerant, dislike dairy or follow a vegan diet, it can be difficult for you to get the right amount of calcium,” Czerwony recognizes. “In these cases, supplements may be the best option.”

Because of some of the risks of calcium supplements, though — including hypercalcemia — you should always speak to a healthcare provider first.

More tips for getting enough calcium

To help your body process calcium, be sure you’re getting enough vitamin D as well.

“Vitamin D helps you absorb calcium, among other functions in the body,” Czerwony says, “and having adequate vitamin D also allows for the right amounts of phosphorous to be absorbed into the body, too.” (Phosphorous, another mineral found in your bones, plays a key role in regulating nerve and muscle functions.)

It’s also important to know that your body can only absorb about 500 milligrams of calcium at a time. What does this mean for you?

“Break up your calcium intake throughout the day,” Czerwony advises. “Don’t take a calcium supplement right after your daily multivitamin, and don’t try to cram all of your calcium-rich foods into a single meal.”