Healthnotes Newswire — Calcium supplements are commonly used to promote bone strength, and are one of the most widely recommended nonprescription therapies for the prevention of osteoporosis. But doctors do not always agree on how much to take and when to take it. A new study,¹ published last month in the American Journal of Clinical Nutrition, found that dosage and timing of calcium supplementation had little effect on markers of bone formation and loss of calcium from bone.

The authors conducted three separate studies: one to evaluate the effects of the timing of calcium intake; one to evaluate the effects of the amount of intake; and one to evaluate the effects of small, repetitive intakes on calcium and bone metabolism. The participants were 30 healthy women, aged 21 to 34 years. After administering calcium supplements according to one of the respective regimens, the researchers measured blood and urine levels of calcium, several hormones, and several biochemical markers of bone formation and breakdown.

Day or Night?

Doctors sometimes recommend that women take calcium supplements at night because it is considered more likely to have a beneficial suppressive effect on parathyroid hormone (PTH), which reaches peak concentrations in the blood at night. The amount of PTH in the blood determines how much calcium is released from bone into the blood; it is therefore an important factor in the development or prevention of osteoporosis. The new study found that the time of day when calcium is taken appears to have no effect on blood levels of PTH, so there is no need to take calcium supplements only at night, at least not by women before they reach menopause.

How Much at a Time?

Previous research has found that dividing the daily amount of calcium supplemented into several smaller amounts increases the percentage of calcium absorbed by the body.² The new study confirmed these findings. However, the new study was unable to show that the amount of calcium taken at any given time affected markers of bone formation and breakdown. Although the effects of calcium on PTH did vary with the amount of the calcium taken in the current study, the authors could draw no conclusions about what calcium regimen is best for bone health in healthy young women.

Even the most positive trials show that calcium supplementation has only minor effects on bone mass. Nonetheless, calcium supplementation plus hormone replacement therapy does appear to be much more effective than hormone replacement therapy without calcium for the prevention of osteoporosis.³ Several clinical trials have also investigated the effects of calcium in premenopausal women, and calcium supplementation has shown a significant beneficial effect on bone mass in these women as well.⁴

Although it remains a controversial topic, the protective effect of calcium against bone loss is one of very few health claims permitted on dietary supplement labels by the U.S. Food and Drug Administration. In order to achieve the 1,500 mg per day calcium intake many researchers consider optimal, 800 to 1,000 mg of supplemental calcium is generally added to the 500 to 700 mg readily obtainable from the diet.