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 used for treatment and prevention of low calcium levels and resulting bone conditions including 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 used for premenstrual syndrome (PMS), leg cramps in pregnancy, high blood pressure in pregnancy (pre-eclampsia), and reducing the risk of colon and rectal cancers.
Some people use calcium for complications after intestinal bypass surgery, high blood pressure, high cholesterol, Lyme disease, to reduce high fluoride levels in children, and to reduce high lead levels.
Calcium carbonate is used as an antacid for “heartburn.” Calcium carbonate and calcium acetate are also used for reducing phosphate levels in people with kidneydisease.
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?”
How does it work?
The bones and teeth contain over 99% of the calcium in the human body. Calcium is also found in the blood, muscles, and other tissue. Calcium in the bones can be used as a reserve that can be released into the body as needed. The concentration of calcium in the body tends to decline as we age because it is released from the body through sweat, skin cells, and waste. In addition, as women age, absorption of calcium tends to decline due to reduced estrogen levels. Calcium absorption can vary depending on race, gender, and age.
Bones are always breaking down and rebuilding, and calcium is needed for this process. Taking extra calcium helps the bones rebuild properly and stay strong.
- 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 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
- 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.
- 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.
- 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. Research also shows that taking calcium supplements might help to keep colorectal cancer from returning. However, people with low levels of vitamin D do not seem to benefit from calcium supplements.
- 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 be more effective 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.
- Stroke. There is some evidence that increasing calcium intake in the diet might decrease the risk of stroke.
- 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.