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Is a bone density test worth the $$?


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Having crunched the numbers on my ovo-vegetarian calcium sources recently, I roughly estimate I have been getting < ~60% RDI, and I have been doing minimal weight bearing exercise.


I read material (eg. https://www.crsociety.org/topic/11299-calcium-bone-health-fracture-risk) that calcium supplementation does not have a significant effect on bone health. Furthermore I am hesitant to supplement anything long term which I can't measure ("can't manage what you can't measure!!!1!"), and a yearly bone density test would leave me out of pocket ~$250 AUD p/a. That's affordable for me, but potentially a waste of money if the test does not inform my decision to supplement.


I am interested in opinions on:


- Is the bone density test worthwhile?

- If it revealed any issues, would supplementation be a part of the solution worthwhile?

- In general, how much do you spend (non-rebate) on medical tests each year to monitor your health?


Alternatively: would it be prudent to ignore supplementing, RDI, and the bone density test, and simply increase my intake of plant based calcium sources + weight bearing exercise?



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Bone health is definitely a concern of many of us long-term CR practitioners and there is at least one horror story of someone practicing CR badly, resulting in very brittle bones and many years of difficult recovery. There is little doubt that the bone mass and bone density of both animals and people practicing CR is reduced, along with fat mass and muscle mass. But as I mentioned in my welcoming message to you, Michael Rae extensively documented (on the old email list - unfortunately not available at the moment  :(xyz) that DEXA scans of bone density are not very useful for predicting fractures in the general population, and especially not in very thin people like us, for whom the machines are very poorly calibrated. Finally, there is direct evidence from this Luigi Fontana study [1] of some of us human CR practitioners that while our bones are less dense, they have strong, high-quality internal structure, meaning (we hope) no serious increased risk of fractures. 


As a result, I don't get regular bone density scans, and in general I don't think other CR practitioners do either. Just be sure to eat nutrient-rich diet. The body is quite good at conserving calcium so 60% of the RDI may be sufficient. But as you know, I supplement with 250mg Calcium per day, along with vitamin K2 and strontium as insurance for bone health. And I would say you should definitely add some weight-bearing exercise to your regime for its bone building benefits.





[1] Aging Cell. 2011 Feb;10(1):96-102. doi: 10.1111/j.1474-9726.2010.00643.x. Epub

2010 Nov 15.
Reduced bone mineral density is not associated with significantly reduced bone
quality in men and women practicing long-term calorie restriction with adequate
Villareal DT(1), Kotyk JJ, Armamento-Villareal RC, Kenguva V, Seaman P, Shahar A,
Wald MJ, Kleerekoper M, Fontana L.
Author information:
(1)Division of Geriatrics and Nutritional Science, Washington University School
of Medicine, 660 S. Euclid Avenue, St. Louis, MO 63110, USA.
Calorie restriction (CR) reduces bone quantity but not bone quality in rodents.
Nothing is known regarding the long-term effects of CR with adequate intake of
vitamin and minerals on bone quantity and quality in middle-aged lean
individuals. In this study, we evaluated body composition, bone mineral density
(BMD), and serum markers of bone turnover and inflammation in 32 volunteers who
had been eating a CR diet (approximately 35% less calories than controls) for an
average of 6.8 ± 5.2 years (mean age 52.7 ± 10.3 years) and 32 age- and
sex-matched sedentary controls eating Western diets (WD). In a subgroup of 10 CR
and 10 WD volunteers, we also measured trabecular bone (TB) microarchitecture of
the distal radius using high-resolution magnetic resonance imaging. We found that
the CR volunteers had significantly lower body mass index than the WD volunteers
(18.9 ± 1.2 vs. 26.5 ± 2.2 kg m(-2) ; P = 0.0001). BMD of the lumbar spine (0.870
± 0.11 vs. 1.138 ± 0.12 g cm(-2) , P = 0.0001) and hip (0.806 ± 0.12 vs. 1.047 ±
0.12 g cm(-2) , P = 0.0001) was also lower in the CR than in the WD group. Serum
C-terminal telopeptide and bone-specific alkaline phosphatase concentration were
similar between groups, while serum C-reactive protein (0.19 ± 0.26 vs. 1.46 ±
1.56 mg L(-1) , P = 0.0001) was lower in the CR group. Trabecular bone
microarchitecture parameters such as the erosion index (0.916 ± 0.087 vs. 0.877 ±
0.088; P = 0.739) and surface-to-curve ratio (10.3 ± 1.4 vs. 12.1 ± 2.1, P =
0.440) were not significantly different between groups. These findings suggest
that markedly reduced BMD is not associated with significantly reduced bone
quality in middle-aged men and women practicing long-term calorie restriction
with adequate nutrition.
PMCID: PMC3607368
PMID: 20969721
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Thanks for the feedback Dean.


In which circumstances would you increase, lower or eliminate your calcium supplementation?


Also, in general, how much $ per year do you spend out of pocket to measure your biomarkers? (which seem pretty extensive from your blood tests spreadsheet)



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Hi Brendan:


I have a wonderfully competent and thorough GP who has three times ordered DXA tests for me.  I am slim compared with the vast majority of the population, but not compared with some people here.  Stress on bones (and muscles of course) makes them stronger, so light people exert appreciably less stress on their bones (and muscles) than the rest of the population which is carrying around a considerable amount of excess body mass.  (Did you ever encounter a bouncer who was slim and 5' 2"?  There is a reason.  And this is it!).  In addition, people with a BMI of 35 have so much protective padding it is doubtful they would break any bones if you dropped them from 40,000 feet.  So, if for no other reason than lack of padding, it is to be expected we will have a greater risk of fracture.  But there are some indications that while we have less bone, as measured by DXA, it appears to be of higher quality. 


In addition, calcium is a two-edged sword.  Too much of it tends to get deposited in artery walls (calcification).  And several studies have found an association between higher calcium intake and risk of prostate cancer, including one done, interestingly, in a country where dairy product intake is zero.


However, a couple of interesting pieces of (anecdotal) information:  adequate vitamin D is probably a lot more important to bones than calcium.  Many years ago (20, perhaps?) my GP tested my 25(OH)D and found it to be a tiny amount below her acceptable range, and prescribed 50,000 IU of D2 weekly for twelve weeks.  It just so happened that a local drug store was offering free bone density tests at the time, using an ultrasound measurement in the heel.  So I had my bone density checked weekly, and for eight weeks this number jumped week-by-week dramatically.  Then after the eighth week went flat, because adequate vitamin D stores had finally been established.  With this experience I am a lot more persuaded about the desirability of adequate vitamin D stores for bone health than for calcium. 


And another point of interest is that fracture frequency increases substantially with age.  Everyone knows this, but many may not know that it increases dramatically with age *even if you maintain the same DXA bone density numbers*.   So there is something to do with bone density that causes increased risk of fracture with age that is not measured by DXA. Which means, imo, that the usefulness - except in extreme cases - of DXA tests is questionable.  Ten years ago I had a "low risk of fracture".  With similar DXA scores measured recently I am now assessed as having a "mid-level risk of fracture".  And in ten more years, if I manage to maintain similar DXA numbers, I will have a "high risk of fracture".


So, it is important as one gets older to start adjusting one's behaviour in ways that will minimize the likelihood of falls and other events that could lead to fracture.  Giving up hang gliding, as an example.  With advancing age fractures heal more slowly, and over age 70 some people find they never properly heal, which leads to reduced mobility which alone can be a serious mortality hazard..


I no longer supplement calcium even though my intake from food appears to be about the same as yours.  My excellent GP frowns on this.  But I do supplement D3 (100,000 IU per month) aiming at a blood 25(OH)D level of between 100 and 125 in SI units.


And of course, I may change my strategy if I come across information I find persuasive.



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In which circumstances would you increase, lower or eliminate your calcium supplementation?


I can't think of any circumstances that would cause me to increase my calcium supplementation, given the recent pretty compelling evidence suggesting it doesn't reduce risk of fracture in the general population. Note: vitamin D supplements didn't either. It wouldn't take too much for me to drop my modest (250mg/day) Ca supplement. 


Also, in general, how much $ per year do you spend out of pocket to measure your biomarkers? (which seem pretty extensive from your blood tests spreadsheet)


Around $300 per year out of pocket. See this post for details.



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Maybe I'm imagining this, but I seem to recall reading maybe 10 years that Luigi (I think) was looking at a correlation between bone strength and fingernail strength, and that an easy test of bone condition via a fingernail sample might come of it. Any truth to this?

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