- Calcium and vitamin D are both necessary for strong, healthy bones.
- Evidence suggests that they are much more effective for bone health when taken together.
- Talk to your healthcare provider about the optimal dose for you.
A strong skeleton is important as you age. It keeps you upright and helps prevent osteoporosis and fractures. Unfortunately, more than 40% of adults age 50 and over have low bone mass—a risk factor for osteoporosis.
It’s no secret that one of the best ways to protect your bones is through nutrition, but there’s more to it than boning up on calcium. In fact, taking calcium supplements without sufficient vitamin D may not be as effective. But is it safe to take the two supplements together? Experts say yes.
“This combination is often recommended to prevent or treat osteoporosis and other conditions related to bone loss,” says Soma Mandal, M.D., a women’s health specialist.
Research backs these claims. For example, one narrative review includes a study that suggests that the combination of calcium and vitamin D was associated with a 19% relative risk reduction for hip fracture. But taking vitamin D or calcium alone was not found to be protective.
Another study found that for postmenopausal women in particular, combined calcium and vitamin D supplementation significantly reduced the incidence of hip fracture.
“This combination is particularly important for older adults and those who may not get enough sunlight or have specific health conditions,” says Taher Saifullah, M.D., a spine and chronic pain specialist. “Vitamin D acts like a key, unlocking the door for calcium absorption in the intestines. Without adequate vitamin D, calcium absorption plummets, hindering bone mineralization and potentially leading to problems like osteoporosis.”
In fact, a vitamin D deficiency could even lead to a calcium deficiency, adds Mandal.
That being said, not everyone needs to take these supplements. If you eat sufficient calcium- and vitamin D-rich foods like fortified dairy products, fatty fish and eggs, and you’re not at risk for deficiency, you probably do not need a supplement. In fact, research suggests that dairy products fortified with calcium and vitamin D can help improve overall bone mineral density in postmenopausal women better than supplements. It appears that dairy may enhance the effect these two nutrients have on bone.
Why You Need Calcium and Vitamin D
You probably know that calcium is important for strong bones, but there’s a lot more that calcium does for the body. The primary functions of calcium are:
- Giving structure to bones and teeth
- Promoting tissue health for normal body movements
- Regulating blood vessel contraction (for cardiovascular health)
- Aiding muscle function
- Supporting blood clotting
- Facilitating nervous system signaling
- Regulating hormone secretion
Vitamin D plays many roles in normal bodily functioning. Spoiler alert: One of them is working in tandem with calcium to promote bone health. Here are the main reasons you need vitamin D:
- Calcium absorption in the gut
- Maintenance of normal calcium and phosphate levels in the blood
- Supporting bone health
- Reducing inflammation
- Metabolizing glucose
- Cellular health
- Immune function
Of course, soaking up the sun is one of the best ways to get vitamin D, but there are real risks to sun overexposure. If you can’t be in sunlight long enough or often enough for your body to manufacture vitamin D, a supplement is probably a good idea for you.
How to Take Your Vitamin D and Calcium Supplements
Dosage
The recommended daily intakes for adults range from 600 to 800 IU for vitamin D and 1,000 to 1,300 mg for calcium. One study found reduced fracture risk from 400 to 800 IU of vitamin D and 1,000 to 1,200 mg of calcium daily among older adults.
That being said, supplementation should fill in any gaps from your diet and account for specific needs you may have based on nutrient deficiencies or health conditions. So if you eat a lot of calcium-rich foods and get a lot of sunlight, you may not need to supplement much, if at all.
Speak with your healthcare provider or a registered dietitian for individualized recommendations based on your diet, health status, medication and supplement regimen and nutrient needs.
Timing
“Take vitamin D with meals that have some healthy fats for better absorption. For calcium, it’s often best to split doses throughout the day, not taking more than 500 to 600 mg at once,” advises Saifullah.
If you are taking a combined calcium and vitamin D supplement, check the dosage and speak with a healthcare provider to determine whether you need to split the dose up or whether you should take it all at once.
Other Factors to Consider
If you’re not sure whether you need a supplement, your healthcare provider can perform a blood test to check your vitamin D levels. A registered dietitian can also help assess your dietary intake of each nutrient to see whether you are meeting your daily needs from food alone. They may want to monitor your levels periodically to ensure they are healthy, says Saifullah.
Furthermore, when selecting a supplement, be sure to purchase one from a reputable manufacturer that has been independently verified for purity and potency, since the FDA does not verify these factors before a supplement is sold.
Potential Side Effects and Risks
Taking vitamin D and calcium is generally safe. However, there are certain risks worth having on your radar.
For one, calcium supplements may lead to gastrointestinal symptoms like constipation, gas and bloating, says Mandal. Plus, too much calcium may increase your risk of kidney stones, especially if you’re not properly hydrated, adds Saifullah. The safe upper limit is 2,500 mg of calcium (or 2,000 mg if you’re 51 or over), an amount unlikely to cause side effects.
Some studies have also found that calcium supplementation may increase cardiovascular risk, although results are mixed and the connection is currently controversial. “In rare cases, excessive intake of these supplements can lead to hypercalcemia (high levels of calcium in the blood), which can cause symptoms like nausea, vomiting, confusion and abnormal heart rhythms,” says Mandal.
Furthermore, these supplements can interact with certain medications, including statins, steroids, thiazide diuretics, levothyroxine, lithium, quinolone antibiotics and dolutegravir. If you’re picking up a calcium supplement at the pharmacy, ask the pharmacist if it might interact with any medication you’re currently taking.
Our Expert Take
There’s no question that calcium and vitamin D are both necessary for optimal health—particularly bone health. Taking them together has proven to be more effective than taking them alone, but there are still potential side effects, especially if you take too high of a dose. Speak with your healthcare provider before starting a new supplement for guidance on the safety and appropriate dosage for you.
