Updated: December 13, 2024

Calcium is a mineral necessary for all living organisms to build bones and keep them healthy. Calcium enables our blood to clot, our muscles to contract, and our heart to beat. About 99 percent of the calcium in our bodies is in our bones and teeth.

Calcium is crucial in growing new bone and maintaining bone strength. The concentration of calcium in the body tends to decline as we age through our skin, nails, hair, sweat, urine, and feces every day. 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.

As our body cannot produce its own calcium, it is important to get enough calcium from the food we eat. When we don't get the required amount of calcium for our body, it is taken from our bones. This can lead to weakening of bones which are prone to break. Not getting enough amount of calcium every day can lead to bone loss, low bone density, and even broken bones. Taking extra calcium helps the bones rebuild properly and stay strong.

Dietary Sources of Calcium

Dietary calcium can be found in several different foods and drinks. We can obtain calcium from a variety of sources. The following foods and drinks are rich sources of calcium:

• Cheese

• Milk

• Seaweeds, such as kelp, hijiki, and wakame

• Yogurt

• Beans

• Nuts and seeds, including pistachio, sesame, almonds, and hazelnuts

• Broccoli

• Figs

• Spinach

• Tofu

• Dandelion leaves

• Many fortified breakfast cereals

Also, many drinks, including soy milk and a variety of fruit juices, are fortified with calcium. If you drink soy milk or another liquid that is fortified with calcium, be sure to shake the container well as calcium can settle to the bottom. Crushed eggshells contain calcium and can be ground into a powder and added to food and drink. A simple way to add calcium to many foods is to add a single tablespoon of nonfat powdered milk, which contains about 50 mg of calcium. It is easy to add a few tablespoons to almost any recipe. Some dark green vegetables may contain high levels of oxalic acid, which reduces the ability of our body to absorb calcium.

Calcium Deficiency

The people at the highest risk of calcium deficiency are postmenopausal women. Since dairy products are one of the most common sources of calcium, people who are lactose intolerant or vegan are also at increased risk of calcium deficiency.

Uses & Effectiveness

Effective for:

• Indigestion: Taking calcium carbonate by mouth as an antacid is effective for treating indigestion.

• 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.

• Hypocalcemia: Taking calcium by mouth is effective for treating and preventing hypocalcemia, a condition in which there is low levels of calcium in the blood. Also, giving calcium intravenously (by IV) is effective for treating very low levels of calcium.

• Hyperkalemia: Giving calcium gluconate intravenously (by IV) can reverse hyperkalemia, a condition in which there is too much potassium in the blood.

Likely Effective for:

• Osteoporosis: Taking calcium by mouth is effective for preventing bone loss and treating osteoporosis. Most bone growth occurs in the teenage years. Bone strength in women remains about the same until age 30 to 40. After age 40, bone loss typically occurs every year. However, in men, this bone loss occurs several decades later. Bone loss is greater in people getting less than the recommended amount of calcium from their diet. Bone loss in women over 40 can be reduced by taking calcium supplements. Taking calcium for 30 years after menopause might result in a 10 percent improvement in bone strength. Taking calcium alone or with vitamin D also helps prevent fractures in people with osteoporosis. Taking calcium along with vitamin D seems to reduce the loss of bone mineral in people using corticosteroid drugs long-term.

• Parathyroid gland disorder: Taking calcium by mouth reduces parathyroid hormone levels in people with kidney failure and parathyroid hormone levels that are too high.

• 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 your diet might prevent PMS. Women consuming an average of 1283 mg/day of calcium from foods seem to have a lower risk of PMS than women who consume an average of 529 mg/day of calcium.

Possibly Effective for:

• Increasing bone strength in fetuses: Calcium supplementation increases the bone mineral density of the fetus in pregnant women who eat a low amount of calcium as part of their diet. However, this does not appear to be beneficial for women with normal calcium levels.

• Colorectal cancer: 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.

• High cholesterol: Taking calcium supplements along with a low-fat or low-calorie diet seems to modestly reduce cholesterol. However, taking calcium alone, without the restricted diet, does not seem to lower cholesterol.

• Tooth loss: Taking calcium and vitamin D by mouth appears to help prevent tooth loss in older people.

• 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 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.

• 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. Increasing calcium intake might help with weight loss. Results are mixed.

Possibly Ineffective for:

• Fractures: Taking calcium alone or with vitamin D does not seem to prevent fractures in older people without osteoporosis.

• Breast cancer: 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. Therefore, taking calcium does not reduce the risk for breast cancer.

• Heart disease: There is no association between calcium supplementation and the risk of heart disease in healthy people.

• Heart attack: 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. 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.

Final Thoughts

Maintaining sufficient calcium levels through diet or supplementation is vital for addressing deficiencies and supporting long-term health. Balancing calcium consumption with lifestyle factors allows its benefits to be fully realized while reducing potential risks.