The Better Bones Blog

by Dr. Susan Brown, PhD.

High calcium intake does not prevent fractures

Years ago, in the first edition of my book, Better Bones, Better Body, I noted that high calcium intakes did not seem to prevent fractures. Cross-cultural data, in fact, suggested that countries with the highest calcium intake actually had the highest rates of osteoporotic hip fractures. Recently, sophisticated meta-analysis of the major published studies on the topic confirm my early breakthrough observation—and go beyond it to suggest possible risks of high, imbalanced calcium intakes. High calcium intakes do not prevent fractures, and may actually increase risk of hip fracture among some.

In my blog post, “Vitamin D is more important than calcium” I report on the US NHANES 111 survey finding that only for women with very low vitamin D levels is a higher calcium intake associated with better bone density. The large national survey (Bischoff-Ferrari et al. 2009) found that if women were not deficient in vitamin D (that is they had a vitamin D level above 20 ng/mL), a calcium intake higher than 566 mg per day was not associated with any greater bone density than with an intake of 566 mg calcium per day.

I doubt this lack of association between bone density and higher calcium intake among all but the vitamin D deficient came as a surprise to Bischoff-Ferrari and colleagues.

And why do I say these researchers were likely not surprised?

Because these scientists had already carefully analyzed all the studies on calcium intake and fracture risk.

• In 2005, Bischoff-Ferrari et al. conducted an overview analysis of studies on vitamin D and fracture prevention and concluded, ‘Thus, additional calcium supplementation may not be critical for non-vertebral fracture prevention once 700-800 IU of vitamin D are provided.” (Bischoff-Ferrari et al. 2005)

• Then again in 2007, the same group conducted a monumental meta-analysis of all major studies looking at calcium intake and risk of hip fracture. As they reported, “Pooled results from prospective cohort studies suggest that calcium intake is not significantly associated with hip fracture risk in women or men. Pooled results from randomized controlled trials show no reduction in hip fracture risk with calcium supplementation and an increased risk is possible. For any nonvertebral fractures, there was a neutral effect in the randomized trials.” (Bischoff-Ferrari et al. 2007)

And what about the possible increased risk of fracture they suggest?

In their meta-analysis they found four clinical trials which reported separate results for hip fracture. These clinical trials involving 6,504 subjects found a 64% greater risk of hip fractures with calcium supplementation. While this question of if, and how, high calcium intake could actually increase hip fracture risk is both complicated and speculative, a logical explanation the researchers mention is that “calcium alone may not prevent hip fractures in women” and that other nutrients are essential for bone strength. The other nutrients they mention include vitamin D, protein, and phosphorus — at least one of which (phosphorus) can be detrimentally impacted by high calcium intakes health.

All this new research supports our long-standing Better Bones position that at least 20 nutrients are key to bone health and that all these nutrients should help keep one nutrient in balance with the others.

 

References:

Bischoff-Ferrari, HA, et al. 2005. Fracture prevention with vitamin D supplementation: A meta-analysis of randomized controlled trials. JAMA, 293(18): 2257-2264.

Bischoff-Ferrari, HA, et al. 2007. Calcium intake and hip fracture risk in men and women: A meta-analysis of prospective cohort studies and randomized controlled trials. Am J Clin Nutr, 86:17980-90.

Bischoff-Ferrari, HA, et al. 2009. Dietary calcium and serum 25-hydroxyvitamin D status in relation to BMD among U.S. adults. J of Bone Miner Res, 24(5):935-942.

 

Vitamin D is more important than calcium

Recently, data from a study of 10,000 Americans supported once again our contention that vitamin D is more important to bone health than is calcium. Even more, this new research suggests that high calcium intakes only aid bone density in those with very low vitamin D status.

Data from the U.S. National Health and Nutrition Examination Survey (NHANES III) published in early 2009, found that calcium intakes of 566 mg per day among women and 626 mg per day among men are likely adequate for those not burdened with low vitamin D levels. Among women only in those very low vitamin D levels (20 ng/mL or less) was there a positive association between calcium intake and bone density. Among women with a greater than 20 ng/mL vitamin D level, a calcium intake of over 566 mg per day was not associated with better bone density than that of women on just 566 mg calcium. Among men, calcium intake was not associated with bone density at any level of vitamin D studied.

So, if we need less calcium than previously thought, a good next question is, “Does higher calcium intake really prevent fractures, anyway?” The authors of this study answer that very question — and their answer is no. Summarizing the findings of more than a dozen large studies, they note the clear lack of association between calcium intake and osteoporosis fracture risk. In fact, a recent, large meta-analysis found higher calcium intakes to actually increase hip fracture risk. For further discussion of these recent findings on calcium intake and fracture see my blog post, “Higher calcium intake does not prevent fractures.”

 

Reference:

Bischoff-Ferrari, HA, et al. 2009. Dietary calcium and serum 25-hydroxyvitamin D status in relation to BMD among U.S. adults. J of Bone Miner Res, 24(5):935-942.

Strong back muscles can lower future fracture risk

Exercise builds muscle and bone, but the benefits are held to disappear upon exercise cessation — or so it appeared, anyway. A recent exercise study from the Mayo Clinic, however, documented powerful spinal fracture reduction eight years after cessation of a back strengthening program. Eight years after stopping this two-year exercise program, past exercisers had significantly greater bone density, and nearly a 2.7 times lower vertebral compression fracture incidence, than non-exercising controls.

This study found that healthy postmenopausal women can reduce their 10-year risk of vertebral fracture by nearly 300% with one simple back exercise performed 5 days a week. As suggested by this study, back-strengthening exercise is far more effective at reducing spinal fracture than any drug therapy and is totally safe — a true Better Bones, Better Body® Approach. Let’s look at the study in detail.

This Mayo Clinic study involved 50 healthy Caucasian postmenopausal women ages 58–75, with no back pain or injury. The women were divided into 2 groups for a 2-year randomized controlled exercise trial. Twenty-seven women performed progressive, resistive back-strengthening exercises, and twenty-three served as non-exercising controls. Measurements were made of back extensor muscle strength, bone mineral density, and spinal deformity.

At baseline, back extensor muscle strength was similar in both groups (exercisers at 39.4 kg and controls at 36.9 kg) and there was no significant difference in bone mineral density. By the end of the 2-year study period, exercisers had increased back extensor strength by some 70% while controls gained 32% in strength and there was no significant difference in bone mineral density between the two groups. At 10 years, the exercising group had lost 16.5% of their baseline back strength (down to 32.9 kg from 39.4) and the control had lost 27.1% of their baseline strength (down to 26.9 from 36.6 kg). The difference in back strength was still significant at 10 years. Overall, exercisers lost 1.65% back muscle strength per year while controls lost 2.7% a year. Bone density declined in both groups, but at 10 years, exercisers had significantly greater bone density than controls. Most importantly, among past exercisers, spinal compression fractures rates were 2.7 lower even 8 years after cessation of the back-strengthening exercise program.

And what was this effective exercise program? Women were instructed in progressive, resistive weight-lifting exercise for the back extensor muscles. They used a backpack that contained weights equivalent to 30% of the maximal isometric back extensor strength. Lying in a prone position (on their stomachs) they lifted the backpack ten times (see illustration). As their back strength increased, the amount of weight lifted was increased. The maximum weight of the backpack was 50 lbs. Women did the 10 repetitions of this back weight-lifting exercise 5 days a week for 2 years.

 

Reference:

Sinaki, M, et al. 2002. Stronger back muscles reduce the incidence of vertebral fractures: A prospective 10-year follow-up of postmenopausal women. Bone, 30(6):836-841.

 


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