Note: The U.S. Food and Drug Administration (FDA) does not approve supplements for safety or effectiveness. Talk to a healthcare professional about whether a supplement is the right fit for your individual health, and about any potential drug interactions or safety concerns.
If you’re concerned you’re not getting enough calcium, you may be considering supplements. There’s no doubt that calcium is essential for strong teeth and bones — and has long been considered a key supplement for preventing bone loss in women — but the way you ingest it matters.
Getting enough calcium from food, rather than supplements, is generally recommended for most people. Calcium supplements may even pose health risks, especially in older adults and women postmenopause.
Some data suggests that calcium supplementation may increase cardiovascular risk, though the findings are mixed. Studies also suggest that calcium supplements may provide limited benefit in reducing fractures, including hip fractures, in postmenopausal women.
Beyond these groups, calcium supplements can cause a range of side effects worth knowing about before you start taking them.
1. May Reduce Nutrient Absorption
Each of these minerals plays a distinct role in the body, but collectively they help transport oxygen throughout the body, support immune health, and regulate muscle function.
If you choose to use calcium in addition to other vitamin and mineral supplements, Dr. Stephenson recommends staggering your intake of each by several hours. This helps ensure that your body is able to absorb each nutrient efficiently.
Calcium supplements also lack the additional nutrients you get when eating calcium-rich foods. “Calcium-rich foods often contain vitamin K, vitamin D, and magnesium. These nutrients help maximize your calcium intake,” says Yoon Hang Kim, MD, MPH, a board-certified preventive medicine physician and integrative functional medicine practitioner in San Antonio, Texas.
2. May Cause Constipation
Unlike food, which contains small, manageable amounts of calcium, supplements slow down the passage of food through the digestive tract. This can cause gastrointestinal (GI) issues like constipation, gas, and bloating.
When you take high-dose calcium supplements, the muscle contractions that help move food through the gut slow down, and fluids secreted by the intestines decrease, making stools harder and more difficult to pass.
If you take calcium supplements, dividing your daily dose into smaller increments may reduce this effect. “The body absorbs calcium most efficiently when calcium supplements are taken in small doses, rather than in one large, daily amount,” explains Shaye Arluk, RDN, a registered dietitian-nutritionist and nutrition and wellness coordinator with Sentara Brock Cancer in Norfolk, Virginia.
3. May Lead to Hypercalcemia
Calcium supplements can trigger the same outcome through a different route. Most adults need between 1,000 and 1,200 milligrams (mg) of calcium per day, and many already get a significant portion of that through food. When supplementation pushes total intake well beyond that threshold, the body can struggle to absorb or excrete the excess, causing surplus calcium to accumulate in the blood rather than being used by bones and tissues.
4. May Interact With Medications
Calcium supplements bind to certain medications, which decreases absorption and reduces their effectiveness. These medications include:
- Thyroid medications like levothyroxine
- Antibiotics used to treat bacterial infections
- Human immunodeficiency virus (HIV) treatments like dolutegravir
To prevent interactions, take your medication several hours before or after taking calcium supplements.
Note that taking calcium supplements alongside lithium, a treatment for bipolar disorder, can also increase the risk of hypercalcemia.
It’s best to consult your healthcare provider before starting calcium supplementation if you take medications, Arluk says.
5. May Raise the Risk of Kidney Stones
Calcium from food may actually work against stone formation. Dietary calcium binds to oxalate in the intestines, preventing it from reaching the kidneys and urine where the most common type of stone, calcium oxalate, forms.
Calcium supplements may not offer the same benefit. Rather than providing the same oxalate-binding effect as dietary calcium, supplemental calcium may increase the amount of calcium released into the urine, especially when taken between meals. This may raise the risk of stone formation.
6. May Increase Heart Disease Risk
One meta-analysis of clinical trials found that taking daily calcium supplements increased the risk of cardiovascular disease by about 15 percent in healthy postmenopausal women.
But these findings remain inconsistent across studies, and more research is needed. Clinical guidelines, for example, note that there’s a lack of sufficient evidence directly linking calcium supplementation to cardiovascular disease.
“Most people can take calcium supplements safely, in moderation,” Dr. Kim says. But he recommends turning to calcium-rich foods instead of supplements if you have a personal or family history of heart disease.
Who Still Might Need Calcium Supplements?
“The only population I ever recommend focusing on supplements are those with a true lactose intolerance or dairy allergy, who cannot get the recommended dietary intake from food alone,” she adds.
If you’re worried that you’re not getting enough calcium from food, discuss your concerns with a healthcare provider. They can help you weigh the risks with the benefits of calcium supplements to determine if supplements are appropriate for you.
The Takeaway
- Calcium supplements can cause side effects, including constipation, reduced absorption of other minerals, and — when taken in excess — hypercalcemia, kidney stones, and may increase cardiovascular risk.
- Getting calcium from food is preferable to supplements for most people, as food sources provide additional nutrients like vitamin K, vitamin D, and magnesium that help the body use calcium effectively.
- Supplements may be appropriate for people with lactose intolerance or dairy allergies who can’t meet their calcium needs through diet. But anyone considering them should consult a healthcare provider first.
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