Strontium ranelate, marketed under the trade name Protelos, is a prescription drug used in the treatment of osteoporosis to reduce the risk of vertebral and hip fractures in postmenopausal women and derives from the chemical element strontium. It is different than other osteoporotic treatments in that it works to both promote bone formation and reduce bone resorption. In other words, strontium ranelate helps bones grow and reduces bone loss.
Strontium is very similar to calcium. Its nucleus is nearly the same size as calcium. Because of this, the body very easily absorbs strontium. There’s also some research that suggests the body metabolizes strontium similarly to calcium.
The body uses vitamin D to help absorb calcium. Studies show that those sufficient in vitamin D absorb more calcium than those deficient. Some researchers consider a vitamin D level of 32 ng/ml the threshold for sufficiency verse deficiency because some research shows that you maximally absorb calcium with vitamin D levels above 32 ng/ml.
Therefore, researchers wanted to know, does vitamin D status also influence the absorption of the drug strontium ranelate? If so, vitamin D status may influence the dose of strontium ranelate prescribed.
Researchers out of Brazil enrolled 50 postmenopausal women into their study who had been diagnosed with either osteoporosis or osteopenia. The researchers segmented the women based on vitamin D levels, with 25 women having vitamin D deficiency (defined as levels below 20 ng/ml) and 25 women having vitamin D sufficiency (defined as levels above 30 ng/ml).
The patients were given one gram of strontium ranelate and the researchers tracked the fraction of absorbed dose at intervals of 30, 60, 120, and 240 minutes.
The researchers then administered the vitamin D deficient group with 50,000 IU/week of vitamin D for 8 weeks to bring them up to sufficiency for another round of analysis. The researchers repeated their strontium ranelate administration and absorption test.
They wanted to know, was there a difference in the way the deficient and sufficient groups absorbed strontium ranelate? And, did supplementing the deficient group change the absorption?
Here is what the researchers found:
- There was no difference in the amount of strontium ranelate absorbed in the deficient vs sufficient groups.
- After the researchers supplemented the vitamin D group and raised their levels above 30 ng/ml, there was still no difference in the amount of strontium ranelate this group absorbed before and after vitamin D treatment.
- In contradiction to some extent, the researchers found that 1,25(OH)2D (active vitamin D) did correlate positively with the fraction of absorbed dose at 120 minutes, the higher the 1,25(OH)2D, the more strontium ranelate absorbed. Mean levels of 1,25(OH)2D did rise before and after vitamin D treatment.
The researchers concluded,
“In summary, the correction of mild vitamin D deficiency is not linked with optimization of strontium ranelate absorption. However, the importance of vitamin D for bone health is irrefutable. Taking into account the benefits of correction vitamin D status in osteoporotic patients, we strongly recommend the treatment of vitamin D deficiency.”
Randomized controlled trials with larger sample sizes should be considered to definitively prove if vitamin D can help enhance strontium absorption. Until then, if you have osteoporosis and are taking strontium ranelate or not, it is important to maintain vitamin D intake for management of the condition. You can find more information on vitamin D and osteoporosis in our health condition summary page.