Salt and osteoporosis

Introduction

Osteoporosis is a condition involving the thinning of bones (bone demineralization), leaving them brittle and more susceptible to fracture. Ninety nice percent of calcium is stored in the bones, so sufficient calcium is important in order to maintain or reach peak bone mass (PBM).

In the UK, an estimated 3 million people are suffering from osteoporosis, with 1 in 2 women and 1 in 3 men over 50 years old breaking a bone at least once, mainly due to poor bone health. Each month, 1,150 people die as a result of a hip fracture. Osteoporosis mainly effects the older population, with 19.8 million people over the age of 50 in the UK. Since the 1960’s there has been a 7 fold increase in the number of osteoporosis cases. Each year osteoporosis costs the NHS approximately 2.3 billion pounds.

Who is most at risk of osteoporosis?

The older population are more at risk of osteoporosis because bones naturally become thinner as we get older. Post-menopausal women are particularly at risk of osteoporosis because of the decrease in the female hormone, estrogen. Those with higher salt intakes are increasing the amount of bone demineralization that takes place.

Studies have also demonstrated that there is a correlation between salt intake and calcium excretion in young and adolescent girls. It has been suggested that this may result in a reduced peak bone mass, which would increase the risk of osteoporosis later in life.  Consuming a low salt diet during adolescent years may therefore be important, to reduce the risk of osteoporosis later in life.

How does Salt Contribute?

Studies dating back to the 1980’s have found possible links between salt intake and urinary calcium (Ca) excretion.

Figure 1 – Changes in hip bone density with different urinary sodium excretions.

A high salt intake increases calcium losses in the urine (calciuria), some of which will be directly from the bones. One study found that for each 100mmol increase in salt intake, urinary Ca is increased by 1.4mmol. If this loss is assumed to be from the bone, then this equates to about 1% extra loss of bone each year.   Over extended periods this would lead to the weakening of bones and ultimately osteoporosis. Both epidemiological studies and randomized trials have shown that a decrease in salt intake reduces urinary calcium excretion. A study in post-menopausal women showed that the loss of hip bone density over 2 years was related to 24-hour urinary sodium at entry to the study, and was as strong as that relating to calcium intake. It was calculated that a reduction in salt intake from 10 to 5 g/day would have the same effect on hip bone density as an increase in calcium intake of 1000mg/day, a difficult amount to achieve without resorting to supplements (Fig 1).  Another study has suggested that in postmenopausal women with a sodium intake of more than or equal to 3.4g/day (8.5g salt), a reduction in salt intake would benefit their bone health.

Blood Pressure, Osteoporosis and Kidney Stones Salt intake and blood pressure are strongly linked, and it is also believed that patients with high blood pressure excrete more calcium in the urine and are, therefore, at higher risk of osteoporosis and kidney stones.  Recently, a study showed sodium to be a major linking factor between blood pressure and osteoporosis. The authors found that hip and spine Bone Mass Density (BMD) were inversely correlated with a higher sodium excretion, i.e. the higher the salt intake, the lower the BMD. They concluded that the increase in calcium excretion is obligatory as a result of the increased sodium in the diet (Fig 2).  Another study showed that a 20mmHg increase in BP is associated with 0.28mmol/day increase in Urinary Ca.

Figure  2 – the link between salt intake, blood pressure and bone mineral loss.

Current Salt Intake & Dietary Advice

Almost everyone in the UK (and the rest of the Western world) eats too much salt. The daily recommended amount in the UK is no more than 6 grams a day; the current average salt intake is 8.6g salt a day although many people are eating more than this.

People with or considered at risk of osteoporosis should ensure that they keep their salt intake below the recommended maximum of 6g. This can be achieved by simple changes, such as consuming less processed foods and checking product labels before purchase. Consuming low salt dairy products such as milk will also help maintain bone mass. Caffeine and fizzy drinks are thought to reduce bone mass, and therefore should be kept to a minimum. An increase in Vitamin D, Zinc and Copper may also be of help.
The original article with references is available here: 

www.worldactiononsalt.com/salthealth/factsheets/osteoporosis

Also see my next post, "Americans Consume Too Much Sodium (Salt)," for information about salt intake in the U.S.A.  

Sequential Treatment with Teriparatide (Forteo) and Strontium Ranelate in a Postmenopausal Woman with Atypical Femoral Fractures after Long-term Bisphosphonate Administration

Abstract

OBJECTIVE:

Despite the existence of numerous case series, no evidenced-based medical management for atypical fractures associated with bisphosphonate (BP) treatment has been established.

DESIGN:

We report the outcome of teriparatide (TRP) administration followed by strontium ranelate (SR) in a woman with a complete and an incomplete contralateral atypical fracture of the femoral diaphysis (AFF) associated with BP treatment. The spontaneous complete AFF was managed with intramedullary nailing, discontinuation of BP and initiation TRP.

RESULTS:

Eleven months later, she suffered a contralateral incomplete AFF. At the completion of the TRP treatment, she had only slight discomfort in the femur with the incomplete AFF. BMD testing revealed increase of 7.61% at the lumbar spine (LS) and 0.8% at the hip. Following TRP, 1-year SR treatment resulted in further BMD increase of 9.2% at the LS and 1.4% in the hip, while she does not report any pain. Bone markers remain within the normal range.

CONCLUSION:

Our case indicates that sequential therapy with TRP and SR in cases of AFF might be a rational treatment option. However, there is a need for additional information concerning the effect of TRP and SR, given alone or sequentially, in these patients in order to incorporate these drugs into the management of AFF.

http://www.ncbi.nlm.nih.gov/pubmed/24457408

Study Demonstrates DXA Scan Is Obviously Flawed

Most clinically important vertebral body compression fractures found on abdominal multidetector computed tomography (CT) scans would go unreported if sagittal reconstructions were not routinely evaluated, according to a new study.

"At this point, it is routine to evaluate sagittal reconstructions at abdominal multidetector CT (MDCT), and whenever vertebral fractures are detected, they are reported." However, this has not always been the case, said Travis Lauder, BS, a fourth-year medical student at the University of Wisconsin School of Medicine and Public Health in Madison.

"The studies we reviewed were done before 2007, when sagittal reconstructions were not automatically provided. We showed that without them, we missed a lot of vertebral compression fractures in patients who underwent abdominal multidetector CT," he explained.

Lauder presented the study results at the American Roentgen Ray Society 2013 Annual Meeting in Washington, DC. First results were published online February 28 in Radiology.

Lauder and his team retrospectively analyzed 2041 consecutive patients (mean age, 70.8 years) who had undergone abdominal multidetector CT and dual-energy x-ray absorptiometry (DXA) within 6 months of each other. The images were taken from 2000 to 2007, before sagittal CT reconstructions were routinely obtained.

The researchers used the Genant visual semiquantitative method to review transverse (axial) and retrospective sagittal multidetector CT reconstructions for the presence of moderate to severe fractures of the lower thoracic and lumbar spine. They also reviewed the electronic medical records of these patients to determine whether the fracture was reported at prospective CT interpretation, was known previously, or was subsequently diagnosed.

"At least 1 moderate or severe vertebral body compression fracture was retrospectively identified on CT in 97 patients," the researchers report. The fractures involved 1 level in 67 patients and 2 or more levels in 30 patients. In total, 141 fractures were identified.

In patients with an unreported fracture, vertebral body compression fracture was not recognized clinically in 64% and there was no evidence of osteoporosis on DXA in 48%.

"DXA is still the gold standard," Lauder noted, "but this analysis demonstrated that a lot of these patients have false negatives on DXA, and that the DXA test is obviously flawed."

Incidental findings are a well-known "double-edged sword" in cross-sectional imaging, said Abraham Dachman, MD, professor of radiology and director of the fellowship programs at the University of Chicago in Illinois, who was asked by Medscape Medical News to comment on the study.

"Many findings — some previously known by the referring physician and some not — can be found on CT. It is often difficult for the radiologist to know what findings to report, what findings to ignore, and what incidental findings are sufficiently important to require personal communication with the referring physician," Dr. Dachman said.

However, this study highlights the potential of abdominal CT to detect vertebral body compression fractures, he noted. Coronal and sagittal reconstructions are often done by the technologist who performs the exam using software on the CT scanner console; they do not require dedicated workstations.

"This study did not address how often the observation of vertebral body compression fractures changed patient management because it was retrospective in nature," Dr. Dachman said. "Still, it highlights the potential of CT to reveal information and provides a rationale to radiologists who wish to routinely report this observation."

This article appeared on Medscape under the title, “Vertebral Fractures Go Undetected without Sagittal Views.”

http://www.medscape.com/viewarticle/782730

The abstract and full text with CT images for “Unreported Vertebral Body Compression Fractures at Abdominal Multidector CT,” which was published in Radiology  in July 2013, can be read here:

http://pubs.rsna.org/doi/full/10.1148/radiol.13121632

For an excellent description of computed tomography (CT) and multidetector computed tomography (MDCT), see:

http://www.amic-chicago.com/Multidetector%20CT.pdf

For a description of an abdominal CT scan, see:

http://www.nlm.nih.gov/medlineplus/ency/article/003789.htm

For information on computed tomography angiography (CTA), see:

http://www.vascularweb.org/vascularhealth/Pages/ct-angiography.aspx

Strontium Citrate and Strontium Ranelate

Strontium ranelate is prescribed for postmenopausal osteoporosis in the United Kingdom, Australia, much of Europe and Asia, and Mexico. Due to an increased risk of thrombosis and cardiovascular events in patients with a history of cardiovascular problems, some doctors are discouraging their patients from taking strontium ranelate or refusing to prescribe it.

Strontium ranelate is not available in the United States or Canada. However, strontium citrate can be purchased as a supplement from health food stores and online distributors. Is strontium citrate safe and effective?

In 2012, Canadian researchers published the Combination of Micronutrients for Bone (COMB) Study. Here is the abstract:

“Along with other investigations, patients presenting to an environmental health clinic with various chronic conditions were assessed for bone health status. Individuals with compromised bone strength were educated about skeletal health issues and provided with therapeutic options for potential amelioration of their bone health. Patients who declined pharmacotherapy or who previously experienced failure of drug treatment were offered other options including supplemental micronutrients identified in the medical literature as sometimes having a positive impact on bone mineral density (BMD). After 12 months of consecutive supplemental micronutrient therapy with a combination that included vitamin D3, vitamin K2, strontium, magnesium and docosahexaenoic acid (DHA), repeat bone densitometry was performed. The results were analyzed in a group of compliant patients and demonstrate improved BMD in patients classified with normal, osteopenic and osteoporotic bone density. According to the results, this combined micronutrient supplementation regimen appears to be at least as effective as bisphosphonates or strontium ranelate in raising BMD levels in hip, spine, and femoral neck sites. No fractures occurred in the group taking the micronutrient protocol. This micronutrient regimen also appears to show efficacy in individuals where bisphosphonate therapy was previously unsuccessful in maintaining or raising BMD. Prospective clinical trials are required to confirm efficacy.”

Here is the COMB protocol for bone health:

(1) Docosahexaenoic acid or DHA (from Purified Fish Oil): 250 mg/day          

(2) Vitamin D3: 2000 IU/day         

(3) Vitamin K2 (non-synthetic MK7 form): 100 ug/day        

(4) Strontium citrate: 680 mg/day (strontium)       

(5) Elemental magnesium: 25 mg/day      

(6) Dietary sources of calcium recommended        

(7) Daily impact exercising encouraged    

The following two paragraphs are quotes from the paper:

“Studies to date have predominantly focused on strontium ranelate rather than the readily available strontium citrate supplement as used in this study. The results of this study, however, demonstrate that the micronutrient combination including strontium citrate is at least as effective in BMD change as strontium ranelate with suggestion of preferred efficacy of the former therapy at improving femoral neck outcomes. Furthermore, the ranelic acid salt is a purely synthetic molecular compound, while citrate is naturally occurring. It appears to be the strontium portion of the molecules which exerts most or all of the positive effect on bone. When consuming the strontium ranelate, for example, the compound splits into two strontium ions and one molecule of ranelic acid, with each absorbed separately. There is little evidence that the ranelic acid portion of the strontium ranelate compound contributes to the effect of strontium on skeletal tissue, and of the small amount of ranelic acid that is absorbed into the body, almost all is excreted within a week without ever being metabolized. All forms of strontium have bioavailabilities in the 25–30% range, but gastric tolerance appears to be better with the ranelate and citrate forms.”

“With the mounting concern about the safety profile of some standard medical interventions for bone compromise, strontium is very well tolerated and has shown remarkably little in the way of side effects or long-term adverse sequelae. An increased risk of thrombosis has been noted with strontium ranelate, an effect not reported (to our knowledge) with strontium citrate [16].”

16. S. J. Genuis and G. K. Schwalfenberg, “Picking a bone with contemporary osteoporosis management: nutrient strategies to enhance skeletal integrity,” Clinical Nutrition, vol. 26, no. 2, pp. 193–207, 2007.
The abstract to reference 16:
 http://www.clinicalnutritionjournal.com/article/S0261-5614%2806%2900151-8/abstract
The entire article (reference 16) in PDF form:
 http://www.uio.no/studier/emner/medisin/nutri/ERN3120/v12/ERN3120-Unit3-Student/02%20Osteoporosis%20and%20Ostaomalacia/Osteoporose-ern%C3%A6ring-03.pdf

The entire COMB Study article can be read here:

http://www.hindawi.com/journals/jeph/2012/354151/#B16