When women think about what they can do to prevent osteoporosis, most women think of calcium supplementation. Calcium improves bone health, increases bone mineral density, and improves the effectiveness of osteoporosis medications. Although most studies do not show a positive effect of calcium reducing fracture risk, in the Women’s Health Initiative (WHI) trial, hip fractures significantly reduced in older women on the calcium supplement program. Calcium supplementation has also been shown to decrease bone loss in postmenopausal women. The effects of calcium supplementation have been greatest in women whose baseline calcium intake was low, in older women, and in women with osteoporosis.
As women age, especially after menopause, calcium requirements increase due to both reduced intestinal calcium absorption and less efficient renal kidney conservation of calcium. Even though these two mechanisms are in play, the primary influence on calcium absorption is the actual amount of calcium that is ingested, either via diet or supplementation. Selected populations of postmenopausal women may not have adequate calcium intake, including older women, women who are lactose (dairy foods) intolerant, vegans (no animal/no dairy), and women on poor diets in general. Even in the U.S., postmenopausal women have dietary intakes of calcium of about 600 mg/day, which is below the recommended amount. The National Institutes of Health (last revised in 1994) and the National Academy of Sciences (last revised in 1997) are the two most well accepted recommended guidelines for calcium intake in women:
The amount of a calcium one takes in a supplement requires first estimating what your dietary intake is. Start with assuming that you get 250 mg per day, not counting the dairy foods or the calcium fortified foods, if you eat 2-3 meals per day. Most women take in an additional 300 mg per day in the form of one serving of dairy. If you take in more than one serving per day of dairy, then add another 300 mg for each serving of dairy, or for each serving of a calcium fortified soy food. If you drink one glass of milk per day, no soy foods or other calcium fortified foods, then your average daily intake is the 250 mg + 300 mg = 550mg/day. So, if you are 55 and postmenopausal, then you need an additional 650 mg/day (totalling 1,200 mg) to 950 mg per day (totalling 1,500 mg per day which falls within the recommendations of 1,200 mg-1,500 mg per day for postmenopausal women, not yet 65 years old.
There is a great deal of confusion and controversy about which form of calcium is best. When the calcium is taken on an empty stomach, calcium citrate are absorbed better than calcium carbonate. In addition, it may be that as women age, and have lower stomach acid production, lower fat absorption, and take in less vitamin D due to less exposure to sunshine and decreased fat absorption, calcium citrate may be a better choice due to these compromising effects on calcium absorption. In most women though, especially in peri menopausal women and postmenopausal women up to age 65, there is no known truly best form. Calcium carbonate is absorbed well when taken with food. Calcium citrate can be taken with food or on an empty stomach, making it more flexible as to timing of your supplement regime.
Calcium supplementation is extremely safe and even in amounts of total calcium intake up to 1,500 mg/day, there is no increase in the risk of a kidney stone. However, in women with a history of kidney stones, calcium supplements are contraindicated until she has medical testing/assessment and supervision. Calcium intake greater than 2,500 mg per day, taking into account diet and supplement, should be avoided. Some women become constipated or have nausea and indigestion with calcium supplementation, especially calcium carbonate. In these cases, calcium citrate will less likely cause these problems.
