Each day, the body loses calcium in the urine, feces, and sweat. These losses have to be replaced by calcium in the diet. If calcium in the diet is not sufficient to cover these losses, the body takes calcium from the bones. Over time, insufficient calcium in the diet leads to negative calcium balance and bone loss (osteoporosis). Adequate calcium intake can help prevent osteoporosis and increase bone mass and strength.

MedicineNet:  How much calcium intake is necessary to prevent and treat osteoporosis?

Dr. Truong: The levels of calcium intake recommended by The National Institutes of Health Consensus Conference on Osteoporosis are:

1. 800 mg/day for children ages 1-10
2. 1000 mg/day for men, premenopausal women, and postmenopausal women also taking estrogen
3. 1200 mg/day for teenagers and young adults ages 11- 24
4. 1500 mg/day for post menopausal women not taking estrogen
5. 1200mg-1500 mg/day for pregnant and nursing mothers

These recommended levels of calcium intake are meant for all people, not just for those with established osteoporosis. Unfortunately, I am afraid that Americans overall are not taking in enough calcium. Surveys have shown that the average woman in the United States receives less than 500 milligrams of calcium per day in her diet.

MedicineNet: How can a woman tell whether she/he has enough calcium in the diet? How do you decide who needs calcium supplements?

Dr. Truong: You can roughly calculate the amount of daily calcium intake by the following method:

1. Excluding dairy products, the average American diet contains approximately 250 mg of calcium.
2. There is approximately 300 mg of calcium in an 8-ounce glass of milk or yogurt, or 16 ounces of cottage cheese.
3. A person on an average American diet who also drinks one glass (8 ounces) of milk will receive an estimated 550 mg of calcium.
4. A person on an average American diet who drinks two glasses of milk (or one glass of milk and 16 ounces of cottage cheese) will receive 850 mg of calcium.

If your calcium intake does not meet the recommended calcium requirements, you can make up the difference either by consuming more dairy products and other calcium rich foods, or by taking calcium supplements. Doctors usually recommend calcium supplements rather than increasing consumption of dairy products. Calcium supplements are easy to use, and calcium from supplements is usually absorbed as well as calcium from milk. Calcium supplements have no calories!

MedicineNet: What calcium supplements do you recommend? How much should one take? What is the best way to take calcium supplements?

Dr. Truong: The most practical and inexpensive form of calcium supplement is calcium carbonate (such as Os-Cal or TUMS) taken with meals. Calcium carbonate is most reliably absorbed if taken with meals.

Daily calcium requirement refers to the amount of elemental calcium consumed. Different calcium salts in calcium supplements contain different amounts of elemental calcium (the actual amount of calcium in the supplement). For example, Os-Cal and Tums are calcium carbonate salts. Each 1250 mg of calcium carbonate salt tablet (such as Os-Cal 500 mg or Tums 500 mg extra strength) contains 500 mg of elemental calcium. A person who needs 1000 mg/day of calcium supplement can take one tablet of Tums 500 mg extra strength (containing 500 mg of elemental calcium) twice daily with meals.

The calcium supplements are best taken in small divided doses with meals. The intestines may not be able to reliably absorb more than 500 mg of calcium all at once. Therefore, the best way to take 1000 mg of a calcium supplement is to divide it in two doses, 1500 mg in three doses.

If constipation and stomach upset occur with calcium carbonate, alternative supplements such as calcium phosphate and calcium citrate (Citracal) can be used.

MedicineNet: What are the side effects of calcium supplements? Are there any issues or concerns patients taking calcium supplements should be aware of?

Dr. Truong: Calcium supplements are safe and generally well tolerated. Side effects of high calcium intake are indigestion and constipation.

Many natural calcium carbonate preparations, such as oyster shells or bone meal, may contain high levels of lead, and probably should not be used.

The total daily intake of calcium should not exceed 2000 mg.

In a 12 year Nurses' Health Study involving 90,000 women, high calcium in diet actually lowers the risk of kidney stones. But taking calcium supplements increases slightly the risk of kidney stones. Scientists believe that taking supplements with meals rather than on an empty stomach may reduce kidney stone risk from calcium supplements.

Most importantly, high dietary calcium intake or taking calcium supplements alone is not sufficient in treating osteoporosis, and should not be viewed as an alternative to or substituted for more potent medications such as estrogens or bone anti-resorptive medications in preventing and treating osteoporosis.

Adequate calcium intake and adequate body stores of vitamin D are important foundations for maintaining bone mass and strength. However, they are not as effective as estrogen and antiresorptive medications both in the prevention and the treatment of osteoporosis.

MedicineNet:  How important is vitamin D in prevention and treatment of osteoporosis?

Dr. Truong: Vitamin D is important for osteoporosis in several respects:

1. Vitamin D stimulates the absorption of our food's calcium from the intestines.
2. Lack of vitamin D causes calcium-depleted bone (osteomalacia) that further weakens the bones and increases the risk for broken bones.
3. Vitamin D along with adequate calcium (1200 mg of elemental calcium) has been shown in some studies to increase bone mass and decreases fractures in postmenopausal women.
4. Furthermore, osteoarthritis (degenerative arthritis) of the knees appears to be worse in patients who are deficient in vitamin D. Patients with osteoarthritis whose body stores of vitamin D are relatively low may benefit from increased vitamin D intake or sunlight exposure.