Calcium is the most abundant mineral in the human body. The average adult has about 2 to 3 pounds of calcium in their body, with about 99% in the bones and teeth. The remaining 1% of body calcium is found in the blood and within cells, where calcium helps with dozens of metabolic processes. This 1% of calcium is so important to maintain that the body will draw on calcium stores in the bones – even at the expense of causing osteoporosis – to keep blood and cellular calcium levels within the proper range. Good dietary sources of calcium include all dairy products and several vegetables such as broccoli, bok choy and kale. A cup of milk contains about 300mg of calcium.
- Promotes strong bones
- Lowers blood pressure
- Reduces risk of colon cancer
- Reduces symptoms of premenstrual syndrome (PMS)
More than 99% of the body's calcium is stored in bones, where it serves both a structural and physiological role. The most obvious need for calcium is to help build and maintain strong bones, but calcium is also important for blood clotting, muscle contraction, nerve transmission, and maintenance of normal blood pressure. There is also some evidence that calcium supplements may be helpful in reducing the risk of colon cancer, regulating heart rhythms and treating premenstrual syndrome (PMS).
For decades, we have known about the important role that calcium plays in achieving and maintaining strong bones -and helping to prevent osteoporosis. More recent research, much of it conducted over the past 5 years, has suggested a number of other beneficial health effects of getting adequate calcium in the diet. Among the more exciting research, scientists have recently shown that eating more calcium-rich foods reduces the risk of colon cancer in men and that women who take daily calcium supplements can cut premenstrual symptoms in half (pain, bloating, mood swings, and food cravings). In other studies, researchers found that adequate calcium intake (along with vitamin D) can reduce blood pressure in women with mild hypertension and in black teen-agers (two groups who rarely consume enough calcium). The hypertensive effects of a high-salt diet tend to be most pronounced among people whose diets are low in calcium. In addition, women who take calcium supplements during pregnancy gave birth to children with healthier blood pressure levels (lower than average for the first seven years of life) - this might reduce the child's risk of developing high blood pressure later in life. If that weren't enough evidence that calcium supplements might be a good idea, there is also some evidence that calcium can even influence mood and behavior. The suggestion comes from a space shuttle study in which hypertensive rats become agitated when consuming a low-calcium diet, but become more calm and relaxed and when their diets contain adequate calcium levels.
Additional functions in which calcium plays a role include:
- Transmission of nerve impulses and control of muscle contractions
- Release of chemical messengers for communication between nerves
- Chemical signaling between cells
- Regulation of hormone and enzyme production and activity (regulation of digestion, fat metabolism, energy production)
- Hormone secretion
- Blood clotting
- Wound healing
Side effects from calcium supplements are rare, but may be possible at extremely high intakes. The Upper Intake Level (UL) for calcium is 2,500mg per day. Intakes above 1500 mg per day have not been associated with any greater benefits than more moderate intakes in the 1200-1500 mg per day range. Calcium - it's not just for bones anymore. The most abundant mineral in the body, calcium is most often associated with strong bones and teeth. After all, the body stores about 99% of its calcium in the skeleton. These calcium stores, however, are much more than idle calcium warehouses - they are actually a very active site of continuous mineral exchange between the bones and the blood. The bones continuously release calcium and other minerals into the circulation, where calcium may play a role in controlling blood pressure, easing PMS (premenstrual syndrome) and fighting colon cancer. Calcium is cheap, easily available and well tolerated as a supplement. Practically nobody consumes enough calcium in their daily diet, so calcium is one of the nutrients for which supplementation is highly recommended.
The Daily Reference Intakes (DRI) recommend the following daily intakes for calcium:
- 1300 mg for ages 9-18
- 1000 mg for adults aged 19-50
- 1200 mg for older adults
- 1500 mg for postmenopausal women not taking hormone replacement therapy
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