Every cell in your bones, heart, and brain needs a steady supply of calcium to work properly. Calcium supplements can help with osteoporosis, heartburn, PMS, and more. However, their use in higher doses comes with certain health risks such as kidney stones. Read on to learn the benefits and risks of supplementing.
What is Calcium?
Calcium is the most abundant mineral in the human body and accounts for about 1-2% of body weight. Each and every cell – in the bones, heart, muscles, and nervous system – need it to work.
Calcium plays essential roles in muscle contractions, blood coagulation, bone and teeth formation, and much more .
Only around 1% of total body calcium is found in the blood; the remaining 99% is stored in the bones and teeth [2, 3].
- Strengthens bones & prevents osteoporosis
- May help prevent colon cancer
- Helps maintain normal blood pressure
- Relieves heartburn
- May prevent pregnancy complications
- Reduces PMS symptoms
- Intake needs to be balanced with other nutrients
- Possibly unsafe in excess amounts
- May increase the risk of kidney stones
- May increase the risk of prostate cancer
- May cause stomach upset
- Reduces iron absorption when taken with meals
The best food sources of calcium are dairy products: milk, yogurt, and cheese [4, 5, 6].
Non-dairy foods naturally rich in calcium include [7, 8, 9, 10, 11]:
- Canned or fresh fish with bones (sardines, sardelles, or even salmon)
- Beef tripe
- Tofu (calcium-set is best)
- Leafy greens (kale, broccoli, sprouts, bok choy, collard greens)
- Nuts (hazelnuts, walnuts, almonds)
- Kidney beans
A healthy and balanced diet should provide most people with all the calcium they need. But some people require more, while others are unable to get enough of this mineral from food. In such cases, supplemental calcium may be a good solution.
As we’ll outline, the balanced intake of calcium along with other nutrients is key to getting the desired benefits while minimizing the risk of side effects.
Benefits of Calcium Supplements
Antacids made of calcium carbonate are effective and FDA-approved for treating mild indigestion and heartburn [12, 13].
2) High Potassium Levels
Intravenous calcium gluconate can reverse heart rhythm issues induced by high potassium blood levels (hyperkalemia); it’s an FDA-approved, first-line treatment .
3) Low Calcium Levels
Oral calcium supplements are effective for treating and preventing low calcium blood levels (hypocalcemia). Intravenous calcium salts are needed for severe hypocalcemia with muscle spasms .
4) Kidney Failure
The buildup of phosphate is a major issue in some patients with kidney failure. Oral calcium carbonate or calcium acetate is effective as a phosphate binder. Calcium acetate (PhosLo) may be a better option, and it’s FDA-approved for this condition .
Calcium and vitamin D are two crucial nutrients for the prevention and treatment of osteoporosis. The National Osteoporosis Foundation (NOF) recommends calcium intake of 1000 mg/day for men aged 50-70 and 1200 mg/day for women aged 51+. Individuals who can’t meet their needs from food sources are advised to take supplements .
Adequate calcium intake from foods and supplements can help prevent osteoporosis in young people and specific types such as glucocorticoid-induced osteoporosis. That said, the evidence for calcium benefits in men is much weaker and requires further investigation [18, 19, 20].
Although calcium supplements are effective individually, most experts suggest combining them with vitamin D, which enhances calcium absorption and instructs the body to use it for bone formation [17, 21].
Premenstrual syndrome (PMS) is extremely common and the exact causes are diverse. Low levels of vitamin D and calcium can trigger PMS or contribute to the symptoms, according to a large review of 28 trials .
According to multiple studies with women suffering from PMS, calcium can relieve many of the symptoms such as anxiety, depression, fatigue, and water retention [23, 24, 25, 26].
7) Bone Strength
Some evidence suggests calcium can improve bone health in physically active people, including athletes, military personnel, and manual workers.
During intense exercise, blood pH levels drop as lactate levels rise. To compensate, the body releases calcium from bones, which increases bone loss if the demand for calcium isn’t met. Calcium supplements might be helpful during these periods of intense strain on the whole body and skeletal system [27, 28, 29].
In one trial with 243 army personnel, calcium and vitamin D improved bone density (BMD) and strength .
In yet another trial, 32 well-trained female athletes were given a meal with ~1,350 mg calcium 90 minutes before strenuous exercise. Calcium reduced the typical bone loss seen with prolonged high-intensity exercise .
In another study with 867 healthy men, calcium with vitamin D also improved BMD, especially in the neck, hips, and spine. However, a large review concluded that more evidence is needed before we can claim that supplementation is beneficial for all non-deficient, healthy, older men .
8) Colon Cancer Prevention
According to several review studies, calcium supplements use is associated with lower colon cancer rates and relapse. Most of the trials found that calcium supplements were more effective when taken with vitamin D at the same time [32, 33, 34, 35].
Calcium supplements may aid in colon cancer prevention by protecting colon cells from the damaging effects of free bile acids. Another way calcium might work is by activating a pathway called APC/beta-catenin, which becomes underactive early in colon cancer. Vitamin D, in turn, helps break down bile acids and enhances DNA repair [36, 37].
That said, the studies don’t prove the actual anticancer effects of calcium supplements. They’re not meant to treat any kind of cancer.
9) High Blood Pressure
Adequate calcium intake might prevent the onset of high blood pressure, according to a large review of over 3,000 people. Calcium intake (via food or supplements) slightly reduced blood pressure, especially in those under 35 years of age, salt-sensitive people, and those with low baseline calcium intake .
However, a meta-analysis of eight low-quality clinical trials and 36,800 participants found no significant effects of a calcium-vitamin D combination on blood pressure. Further studies are needed to confirm the effectiveness of calcium supplements for blood pressure reduction .
10) Pregnancy Complications
Preeclampsia is a sudden high blood pressure during pregnancy, which usually starts around the 20th week. It affects about 5% of pregnant women and can lead to organ damage, pregnancy complications, and even death if left untreated. Adequate calcium intake is an important part of prevention .
According to a large review, calcium supplements (over 1g/day) cut the risk of preeclampsia in half .
Supplementation is particularly important if you don’t get enough calcium from food. The World Health Organization recommends 1.5-2 g/day for pregnant women with low dietary calcium intake. Consult your doctor before supplementing to rule out any risks or interactions .
No valid clinical evidence supports the use of calcium supplements for any of the conditions in this section. Below is a summary of up-to-date animal studies, cell-based research, or low-quality clinical trials which should spark further investigation. However, you shouldn’t interpret them as supportive of any health benefit.
11) Fall Prevention
A review study of more than 16,000 elderly people found that a combination of calcium and vitamin D supplements reduces the risk of falls. Falls are a huge hazard for the elderly and often lead to serious or even fatal fractures .
There is no doubt that adequate vitamin D and calcium balance is important for bone and overall health in the elderly. Together, these nutrients help maintain normal posture and muscle-nerve communication .
But some results with supplementation are less conclusive, with a number of studies failing to find any benefit. Vitamin D appears to play a more important role and drive positive results in fall prevention. The effects of calcium, apart from vitamin D, require further investigation .
12) Fatty Liver
Vitamin D deficiency is common in people with liver disease, which eventually reduces calcium absorption .
In two trials of 120 people with nonalcoholic fatty liver disease, calcium and vitamin D improved several markers of liver damage and heart health (ALT, AST, triglycerides, and LDL cholesterol). Vitamin D alone did not improve liver health [46, 47].
These findings highlight the tight synergy between calcium and vitamin D and their importance for liver, bone, and heart health. However, more research is needed to draw reliable conclusions.
According to the largest review of evidence to-date, carried out by the International Foundation for Osteoporosis, calcium supplements alone don’t reduce the risk of fractures. A combination with vitamin D can modestly reduce the risk, but routine supplementation is not suggested for a general, community-dwelling population .
In a meta-analysis of 33 clinical trials with 51,145 participants, “the use of supplements that included calcium, vitamin D, or both was not associated with a significant difference in the risk of hip fractures compared with placebo or no treatment” .
A clinical trial of 53 people found that calcium and vitamin D enhanced weight loss when combined with a restricted diet. The doses used were 600 mg calcium and 125 IU vitamin D daily .
However, a recent review of 41 studies concluded that calcium supplements don’t increase weight loss .
According to the available evidence, calcium supplements may not help with:
Based on a solid body of clinical evidence, calcium supplements definitely don’t help with:
Side Effects & Safety of Calcium Supplements
Calcium supplements are likely safe for a general population, as well as children and pregnant women, in the amounts that don’t exceed the safe upper limit (more details to follow) .
Possible side effects can occur due to high dosage or interactions with drugs, supplements, and health conditions.
Risk of Kidney Stones
The most well-known side effect of calcium supplements is a modestly increased risk of kidney stones. Data from studies suggest around 17% increased risk. The chance of this happening may be reduced by using the calcium citrate form. Calcium citrate reduces the formation and growth of the most common kidney stones (oxalic acid) [48, 58].
Another relatively common side effect of calcium supplements is stomach upset. Symptoms may include constipation, cramping and bloating. Heartburn and nausea are also possible. Calcium carbonate is most likely to cause these problems, as it requires stomach acid for absorption. So again, choosing the citrate form may minimize this side effect [48, 59].
Decreased Nutrient Absorption
Calcium supplements can inhibit iron absorption when taken with meals. Women have higher iron requirements than men and should take calcium supplements at least 2 hours before or after meals [60, 61].
Over-supplementing calcium may come at the expense of other nutrient deficiencies. When you increase your calcium intake, you need to ensure you are getting sufficient amounts of:
These are important nutrients help calcium work optimally in the body.
Some studies have found that calcium supplements increase the risk of heart disease. However, several large reviews consider the evidence too weak to draw any reliable conclusions.
A 2012 review of 16 studies and over 350k people didn’t find a link between heart disease and calcium supplements .
Two more recent reviews similarly found no evidence of increased risk of heart disease, concluding that calcium intake from all sources below 2,500 mg/day is safe [63, 64].
Reviews by expert panels – including the National Osteoporosis Foundation, the American Society for Preventive Cardiology, and the International Foundation for Osteoporosis – back up this opinion [65, 48].
Concerns have been raised about high calcium intake in men and prostate cancer risk. However, it’s impossible to draw any conclusions yet.
According to a review study including more than 900k men aged 50-70 years, higher calcium intake (over 750 mg/day) increases the risk of prostate cancer .
Other studies found the risk of prostate cancer only increase to a meaningful extent when calcium intake is over 2,000 mg/day [67, 68].
A possible explanation is that high calcium intake ups your vitamin D requirements. Vitamin D protects cells from prostate and other cancer types. To stay on the safe side, make sure you get enough vitamin D if you take calcium supplements [69, 70].
With calcium, more is not better. Below are the maximum daily levels of calcium you should not exceed, including both supplements and food sources. About 5% of women over the age of 50 years surpass these levels by almost 400 mg/day .
Going over the upper tolerable levels for a short while is unlikely to cause any issues, but doing so long-term is unsafe .
|0–6 months||1,000 mg||1,000 mg|
|7–12 months||1,500 mg||1,500 mg|
|1–8 years||2,500 mg||2,500 mg|
|9–18 years||3,000 mg||3,000 mg||3,000 mg||3,000 mg|
|19–50 years||2,500 mg||2,500 mg||2,500 mg||2,500 mg|
|51+ years||2,000 mg||2,000 mg|
Heavy Metal Contamination
Calcium supplements may be contaminated with heavy metals. Analyses discovered lead levels above the safe limits in some products. The “natural sources” of calcium (dolomite, coral calcium, oyster shell) contained the highest levels of lead: 4-12x that of refined supplements! [71, 72, 73]
Supplement-drug interactions can be dangerous and, in rare cases, even life-threatening. Always consult your doctor before supplementing and let them know about all drugs and supplements you are using or considering.
Calcium supplements should not be taken with certain medications, including the following :
- Ceftriaxone: can result in life-threatening damage to the lungs and kidneys
- Dolutegravir, Elvitegravir (HIV): calcium can reduce the effectiveness of these
- Antacids (TUMS, Rolaids, Chooz): combining these may lead to an overdose of calcium
Calcium Supplements & Dosage
The best-researched and most common salt is calcium carbonate. It contains 40% elemental calcium, the highest of any form. On the downside, its absorption rate is relatively low: only around 22%. It is also the least water-soluble calcium salt, making it difficult to use in drinks .
People with low stomach acid will have trouble absorbing calcium carbonate, which needs an acidic environment to dissolve. If you take drugs for acid reflux (such as histamine-2 blockers and proton-pump inhibitors), you are probably one of them [76, 77].
Other forms include calcium orotate, citrate, and hydroxyapatite salts, and coral- or oyster-derived products, to name a few. If you’re looking for a breakdown of the pros and cons of each calcium salt, read through this post.
Most adults need at least 1,000 mg of calcium per day. Women over 50 years need a bit more, 1,200 mg a day. If you are a teenager who is pregnant or nursing, be sure to get at least 1,300 mg calcium per day .
The amount of supplemental calcium you need depends on your diet. If your dietary intake is low, you can supplement with up to 1,000 mg/day, unless directed differently by a doctor. Divided doses of no more than 500 mg work best .
The below doses may not apply to you personally. If your doctor suggests using a calcium supplement, work with them to find the optimal dosage according to your health condition and other factors.
The average daily calcium doses in clinical trials were as follows:
- Bone health: 1,000 to 1,200 mg
- Colon cancer: 1,200 to 2,000 mg
- Fatty liver disease: 500 mg
- Blood pressure: 1,000 to 1,500 mg
- Preeclampsia: 1,000 mg
- PMS: 1,000 to 1,200 mg
- Inflammation: 1,000 mg
This puts the typical calcium dosage in a range between 1,000-1,200 mg/day.
Calcium supplements may strengthen the bones, prevent high blood pressure, help with heartburn, support a healthy pregnancy, and more. They are generally safe and well-tolerated in adequate amounts.
On the downside, they can cause stomach upset and kidney stones. Conflicting evidence links their use to heart disease and other health risks. You can reduce or avoid most of the risks by staying below the upper limit and getting enough of other nutrients: vitamin D, magnesium, and vitamin K. Consult your doctor before supplementing.