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Calcium Safety and Side Effects

Calcium seems to be safe for most people. Calcium can cause some minor side effects such as belching or gas. Taking too much calcium (over 2500 mg/day) might increase the risk of side effects.

Some people shouldn't take calcium unless it is prescribed by their healthcare provider. Calcium should be avoided or used carefully in people who have conditions that cause too much calcium in the blood, such as parathyroid gland disorders and sarcoidosis.

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What other names is Calcium known by?

Acétate de Calcium, Aspartate de Calcium, Bone Meal, Calcio, Calcium Acetate, Calcium Aspartate, Calcium Carbonate, Calcium Chelate, Calcium Chloride, Calcium Citrate, Calcium Citrate Malate, Calcium D-Gluconate, Calcium Disuccinate, Calcium Gluconate, Calcium Glycerophosphate, Calcium Hydrogen Phosphate, Calcium Hydroxyapatite, Calcium Lactate, Calcium Lactogluconate, Calcium Orotate, Calcium Phosphate, Calcium Sulfate, Carbonate de Calcium, Chélate de Calcium, Chlorure de Calcium, Citrate de Calcium, Citrate Malate de Calcium, Coquilles d'Huîtres Moulues, Coquilles d'œuf, Dicalcium Phosphate, Di-Calcium Phosphate, Dolomite, Egg Shell Calcium, Gluconate de Calcium, Glycérophosphate de Calcium, Heated Oyster Shell-Seaweed Calcium, Hydroxyapatite, Lactate de Calcium, Lactogluconate de Calcium, MCHA, MCHC, Microcrystalline Hydroxyapatite, Orotate de Calcium, Ossein Hydroxyapatite, Oyster Shell, Oyster Shell Calcium, Phosphate de Calcium, Phosphate de Calcium Hydrogène, Phosphate de di-Calcium, Phosphate Tricalcium, Poudre d'os, Sulfate de Calcium, Tricalcium Phosphate.

What is Calcium?

Calcium is a mineral that is an essential part of bones and teeth. The heart, nerves, and blood-clotting systems also need calcium to work.

Calcium is taken by mouth for treatment and prevention of low calcium levels and resulting bone conditions including muscle cramps (latent tetany), osteoporosis (weak bones due to low bone density), rickets (a condition in children involving softening of the bones), and osteomalacia (a softening of bones involving pain). Calcium is also taken by mouth to prevent falls and to prevent high levels of the parathyroid hormone (hyperparathyroidism). It is also taken by mouth for premenstrual syndrome (PMS), leg cramps and depression in pregnancy, high blood pressure in pregnancy (pre-eclampsia), and to improve bone development in the baby. Calcium is used to reduce the risk of cancer, stroke, and cardiovascular disease, to increase survival following a heart attack, to help retain teeth in the elderly, and to help with weight loss.

Some people take calcium by mouth to prevent diarrhea and seizures due to sudden decreases in calcium levels. It is also taken by mouth to prevent for complications after intestinal bypass surgery, high blood pressure, high cholesterol, diabetes, metabolic syndrome, Lyme disease, to reduce high fluoride levels in children, and to reduce high lead levels. Calcium is used to prevent vitamin B12 deficiency associated with the medication metformin. It is also used to increase survival in people who have had a heart attack.

Calcium carbonate is taken by mouth as an antacid for "heartburn." Calcium carbonate and calcium acetate are also taken by mouth to reduce phosphate levels in people with kidney disease.

Calcium is used as a mouth rinse to prevent and reduce pain and swelling inside of the mouth following chemotherapy. Calcium is given intravenously (by IV) for very low calcium levels of the blood and related symptoms. It is also used for high potassium levels in the blood, muscle cramps following spider bites, and during CPR (cardiopulmonary resuscitation). Calcium gluconate and gluceptate may be injected as a shot if calcium cannot be given by IV. Calcium-rich foods include milk and dairy products, kale and broccoli, as well as the calcium-enriched citrus juices, mineral water, canned fish with bones, and soy products processed with calcium.

Calcium can interact with many prescription medications, but sometimes the effects can be minimized by taking calcium at a different time. See the section titled "Are there any interactions with medications?"

Is Calcium effective?

Taking calcium can slow bone loss in women after menopause and in elderly men. This can reduce the risk of breaking bones.

Calcium can also decrease the symptoms of premenstrual syndrome (PMS), especially mood swings, bloating, food cravings, and pain.

There is also some evidence that calcium might lower the risk of getting colon cancer, especially among people who have already had small, noncancerous intestinal growths called "polyps."

Calcium also seems to be able to lower high blood pressure, especially in people with kidney disease or in pregnant women.

Taking calcium does not seem to be effective, however, in preventing bone loss in breast-feeding women, or after kidney or bone marrow transplants.

Effective for...

  • Indigestion. Taking calcium carbonate by mouth as an antacid is effective for treating indigestion.
  • High levels of potassium in the blood (hyperkalemia). Giving calcium gluconate intravenously (by IV) can reverse heart problems caused by hyperkalemia, a condition in which there is too much potassium in the blood.
  • Low levels of calcium in the blood (hypocalcemia). Taking calcium by mouth is effective for treating and preventing hypocalcemia. Also, giving calcium intravenously (by IV) is effective for treating very low levels of calcium.
  • Kidney failure. Taking calcium carbonate or calcium acetate by mouth is effective for controlling high phosphate levels in the blood in people with kidney failure. Calcium citrate is not effective for treating this condition.

Likely Effective for...

  • Weakened bones (osteoporosis) caused by corticosteroid drugs. Taking calcium along with vitamin D seems to reduce the loss of bone mineral in people using corticosteroid drugs long-term.
  • Parathyroid gland disorder (hyperparathyroidism). Taking calcium by mouth reduces parathyroid hormone levels in people with kidney failure and parathyroid hormone levels that are too high.
  • Osteoporosis. Taking calcium by mouth is effective for preventing and treating bone loss and osteoporosis. Most bone growth occurs in the teenage years, and then bone strength in women remains about the same until age 30-40. After age 40, bone loss typically occurs at rates of 0.5% to 1% per year. In men, this bone loss occurs several decades later. There is more bone loss if less than the recommended amount of calcium is obtained from the diet. This is very common among Americans. Bone loss in women over 40 can be reduced by taking calcium supplements. Some researchers estimate that taking calcium for 30 years after menopause might result in a 10% improvement in bone strength and a 50% overall reduction in the rate of bone break.
  • Reducing symptoms of premenstrual syndrome (PMS). There seems to be a link between low dietary calcium intake and symptoms of PMS. Consuming calcium daily seems to significantly reduce mood swings, bloating, food cravings, and pain. Also, increasing the amount of calcium in one's diet seems to prevent PMS. Women consuming an average of 1283 mg/day of calcium from foods seem to have about a 30% lower risk of developing PMS than women who consume an average of 529 mg/day of calcium. Taking calcium supplements, however, does not seem to prevent PMS.

Possibly Effective for...

  • Colorectal cancer. Research suggests that high intake of dietary or supplemental calcium reduces the risk of colorectal cancer. However, some conflicting evidence exists. This may be due to differences in blood levels of vitamin D. People with low levels of vitamin D do not seem to benefit from calcium supplements.
  • Increasing bone strength in fetuses. In pregnant women who eat a low amount of calcium as part of their diet, calcium supplementation increases the bone mineral density of the fetus. However, this does not appear to be beneficial for women with normal calcium levels.
  • Fluoride poisoning. Taking calcium by mouth, together with vitamin C and vitamin D supplements, seems to reduce fluoride levels in children and improve symptoms of fluoride poisoning.
  • High cholesterol. Taking calcium supplements along with a low-fat or low-calorie diet seems to modestly reduce cholesterol. Taking calcium alone, without the restricted diet, does not seem to lower cholesterol.
  • High blood pressure. Taking calcium supplements seems to reduce blood pressure slightly (usually around 1-2 mmHg) in people with or without high blood pressure. Calcium seems to work best in salt-sensitive people and people who normally get very little calcium. Taking calcium by mouth also seems to be helpful for reducing blood pressure in people with serious kidney disease.
  • High blood pressure during pregnancy (pre-eclampsia). Taking 1-2 grams of calcium by mouth daily seems to reduce pregnancy-related high blood pressure. Calcium appears to reduce the risk of high blood pressure in pregnancy by about 50%. Calcium appears to have the greatest effect in high-risk women and women with low calcium levels.
  • Tooth loss. Taking calcium and vitamin D by mouth appears to help prevent tooth loss in older people.
  • Weight loss. Adults and children with low calcium intake are more likely to gain weight, have a higher body mass index (BMI), and be overweight or obese compared to people with high calcium intake. Researchers have studied whether increasing calcium intake might help with weight loss. Some clinical research shows that increasing calcium consumption from dairy products, such as yogurt, increases weight loss, lean body mass, and body fat loss in people on a low-calorie diet as well as people on a regular unrestricted-calorie diet. Also, taking calcium supplements along with vitamin D seems to increase weight loss in people who have inadequate intake of calcium. Calcium supplements don't seem to increase weight loss in people with adequate calcium intake. Also, calcium does not appear to increase weight loss in people who are not overweight.

Possibly Ineffective for...

  • Breast cancer. Some research suggests that women who eat more calcium have a reduced risk for developing breast cancer. However, other research suggests that blood levels of calcium are not linked with breast cancer risk. Overall, most research suggests that taking calcium does not reduce the risk for breast cancer.
  • Heart disease. Most research shows that there is no association between calcium supplementation and the risk of heart disease in healthy people.
  • Heart attack. Early research suggests that people who consume more calcium in their diet have a lower risk of having a heart attack. However, the effects of calcium SUPPLEMENTS on heart attack risk are not clear. Some research suggests that calcium supplements increase heart attack risk. Other research shows there is no effect. It may be that some people have an increased risk while others do not. For example, people who take calcium as a single supplement might have an increased risk. On the other hand, people who take calcium with vitamin D do not seem to have an increased risk. Also, people who take a calcium supplement and consume more than 805 mg/day of calcium as part of their diet might be at an increased risk, while people who take a supplement and consume less calcium in their diet might not.

Ineffective for...

  • Cardiac arrest. Evidence suggests that administering calcium during cardiac arrest does not increase survival and might actually worsen the chance for resuscitation.

Insufficient Evidence to Rate Effectiveness for...

  • Cancer. Research shows that taking calcium alone does not reduce the risk of cancer. Taking calcium along with vitamin D might reduce the risk of cancer in some people, but results are conflicting. Some research shows that taking 1400-1500 mg of calcium daily plus 1100 IU of vitamin D3 (cholecalciferol) daily lowers the risk of developing cancer by 60% in healthy older women who have low blood levels of vitamin D before treatment. But other research shows that taking 1500 mg of calcium daily plus 2000 IU of vitamin D3 (cholecalciferol) daily does not reduce the risk of developing cancer in healthy older women who have adequate levels of vitamin D before treatment.
  • Diabetes. Some early research suggests that consuming more calcium from the diet or from supplements, either alone or in combination with vitamin D, lowers the risk of developing type 2 diabetes.
  • High levels of lead in the blood. Some research suggests that taking calcium supplements does not lower the levels of lead in the blood. However, other research suggests that taking calcium reduces blood lead levels by 11%.
  • Endometrial cancer. Taking calcium supplements might reduce the risk of developing endometrial cancer. However, dietary calcium does not seem to have any benefit.
  • Preventing falls. Evidence suggests that calcium plus vitamin D might help prevent falls by decreasing body sway and helping to keep blood pressure normal. Calcium alone does not seem to have the effect. Interestingly, calcium plus vitamin D seems to prevent falls in women, but not in men.
  • Stroke. There is some evidence that increasing calcium intake in the diet might decrease the risk of stroke. Other evidence suggests that increasing calcium intake does not reduce the risk of stroke.
  • Metabolic syndrome. Some evidence suggests that consuming more calcium from the diet and supplements, either alone or in combination with vitamin D, lowers the risk of developing metabolic syndrome.
  • Vitamin B12 deficiency caused by the drug metformin. Taking calcium supplements might reduce vitamin B12 deficiency caused by the diabetes drug metformin.
  • Ulcers in the lining of the mouth. Evidence suggests that using a mouth rinse containing calcium phosphate (Caphosol, EUSA Pharma) in combination with fluoride treatments reduces the duration of pain in people with mouth ulcers due to stem cell transplants.
  • Ovarian cancer. Early evidence suggests that high blood levels of calcium are linked to a reduced risk of ovarian cancer. However, other early research suggests that dietary calcium intake is not linked with the risk of ovarian cancer.
  • Depression after pregnancy (postpartum depression). Early research suggests that taking calcium daily, beginning 11-21 weeks into pregnancy, reduces depression at 12 but not 6 weeks after delivery.
  • Pregnancy-related leg cramps. Early research shows that calcium can help prevent leg cramps in the second half of pregnancy.
  • Prostate cancer. Research about how calcium affects the risk of prostate cancer has shown conflicting results. Some research suggests that taking calcium supplements daily decreases the risk of prostate cancer. However, other research suggests that there is not a link between calcium intake and the risk for developing prostate cancer.
  • Seizures. Early research suggests that calcium might help control seizures resulting from sudden drops in blood levels of calcium.
  • Lyme disease.
  • Other conditions.
More evidence is needed to rate the effectiveness of calcium for these uses.

Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, and Insufficient Evidence to Rate (detailed description of each of the ratings).

Therapeutic Research Faculty copyright

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