More Than Vitamin D for Women's Bone Health

Vitamin D and calcium in postmenopausal women affected bone health differently

(RxWiki News) "Take vitamin D," "Drink your milk," "Get enough calcium" — there are a lot of different recommendations about what is best for bone health. A new study aimed to explore the specifics of certain supplements and determine what can most help older women keep their bones strong.

The new study looked at both vitamin D and calcium supplementation in postmenopausal women.

The researchers found that while calcium supplementation seemed to improve bone health, vitamin D supplementation did not have a major effect on measures of bone health.

"Talk to your doctor about which supplements are best for you."

Led by John Aloia, MD, of Winthrop University Hospital in Mineola, New York, this study looked at 159 healthy women at a New York hospital. All the participants were white and postmenopausal.

The women were followed for six months, and 120 of the initial participants completed the study.

The participants were divided into four groups. One group was given 1,200 milligrams of calcium and a placebo (fake supplement) each day, one group was given 100 micrograms of vitamin D3 and a placebo each day, one group was given both vitamin D3 and calcium each day and one group was given two placebos each day.

Urine and blood serum samples were taken from the participants at the study's start, three months later and at completion of the study at six months. Dr. Aloia and colleagues were looking for indicators of bone health, including parathyroid hormone (PTH) levels and bone turnover.

Bone turnover is a naturally occurring process by which the body tears down old bone and replaces it by creating new bone. As women age, however, the process can start to speed up as old bone deteriorates faster than it can be replaced with new bone.

In a healthy person, low blood levels of calcium result in an increase of PTH, causing the body to increase the amount of calcium in the blood. High calcium levels in the blood result in a decrease of PTH, allowing the blood levels of calcium to decrease. Someone who has a consistently high blood level of PTH may be calcium deficient.

The researchers found that the participants receiving calcium had reduced PTH and better bone health markers. Vitamin D did seem to lower PTH, but not as much as the calcium. And in terms of bone turnover indicators, calcium came out on top.

"Supplementation of the diet with 1,200 mg calcium a day reduces bone turnover markers, whereas supplementation with up to 100 micrograms of vitamin D3 a day does not," the study authors concluded.

In a news release, Dr. Aloia explained that this finding does not discount completely the potential benefits of vitamin D.

“Vitamin D and calcium interact to suppress bone turnover by decreasing parathyroid hormone levels. This can be beneficial in women who are vitamin D deficient," explained Dr. Aloia. "In women who already are receiving the recommended daily allowance of vitamin D, however, the study found there was no advantage to adding a vitamin D supplement.”

Dr. Aloia did stress the need for women to discuss possible supplementation with their doctor.

“Women do need to be cautious about the possibility of vascular side effects from too much calcium and should consult their physicians about whether their diet is adequate or whether they should take supplements at all,” noted Dr. Aloia.

"The best advice is to balance any calcium intake with magnesium and aim for a more moderate calcium intake of 600-700mg per day such as followed in the UK and at the WHO. Dietary sources of calcium can meet this requirement especially if dairy, fish with bones and bone broths are eaten. Another necessary mineral in bone health is magnesium, which should be taken in amounts equal to calcium," Carolyn Dean, MD, ND, Medical Advisory Board Member of the non-profit Nutritional Magnesium Association, told dailyRx News. "Vitamin K is also important because it directs the calcium that is absorbed by vitamin D into the bones."

"Approximately 30 to 40 years ago, doctors began prescribing calcium on a routine basis to many men and almost all women over the age of 40 to counter the effects of bone loss due to aging. The conventional wisdom was that bone loss is due to calcium deficiency. After 40 years, it has become clear that taking calcium alone does not stop or even slow bone loss and does not prevent osteoporosis," explained Dr. Dean.

"The new wisdom now emerging is that magnesium is actually the key to the body's proper assimilation and use of calcium as well as vitamin D. If we consume too much calcium without sufficient magnesium, the excess calcium is not utilized correctly and may actually become toxic, causing painful conditions such as some forms of arthritis, kidney stones, osteoporosis and calcification of the arteries leading to heart attack and cardiovascular disease," said Dr. Dean.

This study was published online September 24 in the Journal of Clinical Endocrinology & Metabolism (JCEM). The study was supported by both Merck, a pharmaceutical company, and by New York State's Empire Clinical Research Investigator Program. No conflicts of interest were reported.

Review Date: 
September 23, 2013