How do vitamin D and calcium work together?

Vitamin D and calcium have a close relationship in your body. Without vitamin D, it’s hard for calcium to do its job to keep your bones healthy. 

It’s important to get enough vitamin D because it works hand-in-hand with calcium to keep your muscles, heart, and hormones working well. If you’re low on calcium, you may need to increase both calcium and vitamin D to improve your health. Read on to learn more about how to get enough of these two essential micronutrients.  

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Since vitamin D and calcium work closely together in your body, getting enough of these essential nutrients can affect your bone health, especially in the long-term. 

Vitamin D is essential for getting calcium into your bloodstream, which is why a vitamin D deficiency can lead to a calcium deficiency as well (Ross, 2011). Vitamin D also helps your gut and kidneys absorb calcium. To avoid deficiencies, make sure you eat foods containing vitamin D and calcium. Adults should be getting 1000-1300 mg of calcium daily through their diet, but guzzling milk isn’t a magic bullet (Institute of Medicine, 2011). 

If you have a chronic condition that impacts your ability to absorb nutrients, supplements may be a good option for you. If your healthcare provider prescribes a calcium supplement with vitamin D, it’s usually because these two nutrients work best when paired together. 

Without vitamin D, calcium cannot function properly in your body. A common misconception about bones is that they remain the same throughout your adult life, but this isn’t true. 

Bones are constantly releasing minerals and then rebuilding themselves. Calcium is the key player when it comes to forming the sturdy structure of your bones; without it, they would be soft and wouldn’t be the strong structures you use to move your body every day. It’s important to get enough calcium, but your best bet for bone health is to consider how much vitamin D you’re getting as well.  

If you’ve been diagnosed with a calcium deficiency, you’re not alone. Low calcium is common, especially in parts of the world where people consume less dairy, such as east Asia (Balk, 2017). 

But even if you consume plenty of calcium through your diet, it’s still possible to be low on calcium. People most at risk for low calcium include (Beto, 2015):  

• Those who are lactose intolerant

• Post-menopausal women

• Women who don’t menstruate

• Female athletes

Women’s hormone levels can affect bone health, too. Women who don't menstruate, or have stopped menstruating due to menopause have a harder time keeping their calcium levels stable. This is because estrogen helps the body take in calcium and post-menopausal women or women who don’t menstruate have lower levels of estrogen (Sullivan, 2017). 

Female athletes can experience an imbalance between their exercise habits and their nutrition, which can contribute to low calcium as well (Goolsby, 2017). 

When people can’t tolerate dairy, finding good sources of dietary calcium may be more challenging and can lead to calcium deficiencies. Many of the best sources of calcium are dairy products, but fortunately, there are other food options to consider. 

Symptoms of a calcium deficiency

The symptoms of low calcium can be subtle, and you might be deficient for a while before noticing anything unusual. 

As you age, you are at a higher risk for osteoporosis, a condition that affects the strength of the bones and is related to low calcium. As this condition develops, you may notice loss of height or increased weakness. 

People with osteoporosis often experience falls as well as an increased risk of fractures (Sozen, 2017). Vitamin D deficiencies increase the risk of developing this condition, as well as fractures—often the first sign bones are becoming more fragile. 

A vitamin D deficiency can also cause low calcium since your body can’t use calcium properly without vitamin D (Goyal, 2020). 

We’ve seen why getting enough calcium is important, now let’s talk a look at vitamin D. 

By increasing your body’s ability to hold on to calcium, vitamin D boosts the levels of calcium in your body. But that’s not all vitamin D does. Nicknamed the sunshine vitamin, vitamin S also plays an important role in keeping your skin, immune system, and heart healthy (Khammissa, 2018).  

Besides helping your body absorb calcium, vitamin D appears to have multiple roles in your brain (Bivona, 2019). It helps your brain develop and protects neurons from damage, and there’s even some evidence that supplementing with vitamin D can reduce the risk of dying from cancer (Zhang, 2019). 

Research shows that around two in five Americans don’t get enough vitamin D. Deficiencies are also more common in Black people, as well as those with a history of diabetes, obesity, and cigarette smoking. 

Since dairy milk is often fortified with vitamin D, those who don’t drink it might not be getting enough vitamin D from their diet. Similar to a calcium deficiency, the symptoms of a vitamin D deficiency may not be all that bothersome initially so you might not be able to tell if you have one (Parva, 2018). 

When it comes to vitamin D, where you live matters a lot. Researchers have found that if you live north of an imaginary line running east to west through Louisiana, you’re more likely to have a vitamin D deficiency. In winter, cold temperatures keep people indoors. Add the decreased daily sunlight, and it becomes challenging to absorb enough vitamin D from the sun (Holick, 2011). 

Here’s a look at what other groups are at risk for developing a vitamin D deficiency (Gani, 2015):

• Elderly people

• Those with a body mass index (BMI) over 30

• People who have had gastric bypass surgery

• Those who live with Crohn’s disease, cystic fibrosis, or liver disease

Symptoms of vitamin D deficiency

Many of the signs and symptoms of a vitamin D deficiency is related to bone health. Vitamin D deficiencies can cause both children and adults to develop osteomalacia, which is the softening of bones (Murshed, 2018). When your bones aren’t firm and sturdy, it can put you at risk for pain and fractures. 

The most common symptoms of vitamin D deficiency include bone pain, fatigue, muscle pain, and joint pain (Sizar, 2020). As you can see, the symptoms of vitamin D deficiency and calcium deficiency run parallel to each other since they have such a close working relationship in the body.  

While adults deficient in vitamin D may experience unpleasant symptoms, children who don’t get enough can develop a condition called rickets. Rickets impacts how bones grow, resulting in pain and improper bone growth that can be permanent. Children with this condition are also at a higher risk of fractures (Munns, 2016). 

A blood test can help determine if you don’t have enough vitamin D or calcium in your body (Pils, 2019). If you’re diagnosed with a calcium or vitamin D deficiency, you can increase the levels of your body through diet or supplements, or a combination of both. 

Technically you can get vitamin D from the sun, but it’s best to get it from your diet for a couple of reasons. First off, the type of light the sun gives off can damage your skin, and increase your risk for skin cancer (Watson, 2016). Plus, many people live in parts of the country where sunlight is in short supply during the winter months, making it an unreliable source of vitamin D. 

If sunlight is in short supply, you can turn to vitamin D-rich foods to get your daily intake. 

Vitamin D is found naturally in fewer foods than other micronutrients but is fortified in dairy products like milk. Recent studies also saw benefits in fortifying bread with vitamin D (Nikooyeh, 2016). Some foods high in vitamin D include (NIH, 2020):

• Cod liver oil

• Trout

• Sockeye salmon

• Mushrooms 

• Fortified milk 

For people who are lactose intolerant, vegan, or vegetarian, mushrooms are a great option for increasing the amount of vitamin D in your diet. And let’s not forget about calcium.  

Calcium is common in many dairy products, some fruits, and soy products. Increase your dietary calcium by eating more of the following foods (NIH, 2020):

• Low-fat yogurt

• Orange juice

• Part-skim mozzarella 

• Sardines

• Cheddar cheese

• Low-fat milk

• Soymilk

• Tofu   

How well your body can absorb vitamin D and calcium is an important piece of the puzzle, too.  

Many factors affect bioavailability, or how easily your body can absorb nutrients from food or supplements. 

Recent surgery, digestive conditions, and issues with your kidneys or liver can make it more challenging to get enough vitamin D or calcium (Pressman, 2017). If you can’t get enough calcium and vitamin D from diet alone, a healthcare provider may recommend you take a supplement. 

For people without a deficiency, the daily recommended amount of vitamin D ranges from 400 to 1000 IU. This range helps most people maintain sufficient levels in their bodies (Cashman, 2017). 

When it comes to calcium, the average is 1000 to 1300 mg of calcium daily for most (Ross, 2011). The exact amount somebody should take in every day—from diet or using supplements—depends on their age, sex, and overall health. 

If you’re diagnosed with a deficiency, a healthcare provider may recommend higher daily doses of these nutrients until the levels in your body return to normal. If you’re looking into supplements, it’s important to know what form to take.   

Vitamin D comes in two forms: vitamin D2 and vitamin D3. Vitamin D2 is called ergocalciferol and comes from plant sources. Vitamin D3, cholecalciferol, comes from animal sources. While these two forms of vitamin D serve similar purposes in your body, there is some evidence that vitamin D3 may be more effective than vitamin D2 at raising your levels (Tripkovic, 2012). 

Many different forms of calcium are also available over the counter. The two most common supplements are calcium citrate and calcium carbonate. Calcium citrate can be taken with or without food, but calcium carbonate works better when taken with a meal. Calcium carbonate may cause side effects like constipation and bloating. 

Sticking to the recommended daily dosages is important, even when it comes to supplements. Less is often more with calcium supplementation as your body’s ability to absorb calcium decreases with higher doses (Ross, 2011). 

It’s possible to take too much calcium. Studies show that when people take high doses of calcium supplements, it can negatively affect how their heart and blood vessels work. 

However, eating foods high in calcium does not negatively affect the heart and blood vessels (Tankeu, 2017). As it comes with fewer potential side effects, it’s best to get the calcium you need from your diet.  

There are also some side effects to be wary of when taking combination calcium and vitamin D supplements. Research has found taking vitamin D and calcium together may help reduce the risk for bone fractures. However, other studies point out the risks of side effects—like kidney stones, digestive issues, and heart problems—outweigh the benefits of fracture risk reduction (Yao, 2019; Reid, 2015). 

While rare, it’s also possible to take too much vitamin D. The trick to getting the right amount of vitamin D is balance. If you take too much, the supplement won’t help the way you want it to. Plus, it can cause some unpleasant side effects (Galior, 2018). 

If a healthcare provider prescribed a vitamin D supplement for you, your best bet is to take the dosage prescribed. It’s also important to eat vitamin D-rich foods—getting nutrients like these from the food you eat is always the best way.   

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Current version

February 25, 2021

Written by

Caitlin Knudsen, RN, BSN

Fact checked by

Yael Cooperman, MD

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About the medical reviewer

Yael Cooperman, MD, Ro

Yael Cooperman is a physician and works as a Senior Manager, Medical Content & Education at Ro.