Calcium, vitamin D and the loading of bone

Updated 10 Oct 2026

The current food estimate answers only part of the question

The latest saved food estimate contains about 2,153 mg calcium and 4 µg vitamin D. The calcium number is dominated by approximately 1,814 mg attributed to the confirmed whole 32 oz tub of nonfat yogurt. The narrow displayed calcium scenarios do not cover uncertainty in the online label; they should not be mistaken for a precise measurement.

For the selected male 19–30 reference, the calcium RDA is 1,000 mg/day and its upper limit is 2,500 mg/day from all sources. Vitamin D has a separate RDA of 15 µg (600 IU) and an upper limit of 100 µg (4,000 IU) from food and supplements. These are planning references, not a prescription to keep both nutrients near their upper limits. Original calcium and vitamin D adequacy tables, printed pp.349/363, Original upper-limit tables, printed pp.419/441.

The log does not establish a calcium shortage. Food vitamin D is below its intake reference, and vitamin D was explicitly not taken on this reported day. That still does not establish my blood vitamin D concentration, because the food estimate is not a measure of sunlight exposure, absorption or body stores.

A positive fracture trial in a particular training environment

An eight-week randomized trial enrolled 5,201 female Navy recruits undergoing basic training. Daily supplements supplied 2,000 mg calcium plus 800 IU vitamin D, or placebo. Confirmed stress fractures occurred in 5.3% versus 6.6% of recruits, respectively: a relative risk of 0.80, with a 95% confidence interval of 0.64–0.99. The approximate absolute difference was 1.3 percentage points. Lappe et al., 2008.

This is a clinically useful outcome rather than merely a blood marker. It is also specific to women exposed to a demanding, standardized military program. The intervention combined two nutrients, baseline vitamin D status was not measured, and withdrawal was substantial. The trial therefore cannot identify which component caused the benefit or establish the same benefit in a young man already eating a calcium-rich diet.

The research dose is particularly unsuitable to copy into the current food estimate: adding 2,000 mg supplemental calcium to roughly 2,153 mg food calcium would exceed the applicable total-intake upper limit. A positive study does not erase its starting conditions or the rest of my diet.

Improving vitamin D did not always reduce fractures

The contrasting trial is unusually informative because low vitamin D was common at baseline. A Mongolian school study randomized 8,851 children aged 6–13 to 14,000 IU vitamin D weekly or placebo for three years; 8,348 contributed to its fracture and safety analysis. About 95.5% had baseline 25-hydroxyvitamin D below 50 nmol/L. Children with clinical rickets were excluded. Fractures were reported in 6.4% versus 6.1%, with an adjusted risk ratio of 1.10 (0.93–1.29): no demonstrated fracture reduction. Ganmaa et al., 2024.

This does not mean that treating rickets or another diagnosed deficiency disorder is useless. Those children were excluded, and the study tested prevention of ordinary fractures rather than treatment of that disease. Nor does a childhood trial answer every question about adult stress fractures. It does challenge the broad claim that correcting a low laboratory concentration necessarily prevents fractures in any population.

More bone mineral density can coexist with a null fracture result

In the Women’s Health Initiative, 36,282 postmenopausal women received 1,000 mg elemental calcium plus 400 IU vitamin D daily, or placebo, for about seven years. Hip bone mineral density was 1.06% higher with supplementation, but the intention-to-treat analyses did not show significant reductions in hip, clinical spine or total fractures. Kidney stones were more frequent: hazard ratio 1.17 (1.02–1.34). Jackson et al., 2006.

The population and pill regimen differ greatly from my food routine. The stone finding does not establish that my yogurt causes stones. It shows that a favorable intermediate outcome and an apparently sensible nutrient combination can coexist with no clear benefit on the primary clinical concern and a measurable adverse effect.

“Elemental calcium” also matters: the amount of calcium supplied is different from the weight of the compound containing it. A study’s 1,000 mg elemental dose is not interchangeable with 1,000 mg of calcium carbonate as a chemical compound.

Bone also responds to the training stimulus

A 12-month study compared resistance training twice weekly with jumping three times weekly in physically active men with low hip or spine bone mineral density. Thirty-eight men completed the study, with a mean age around 44. Both groups received 1,200 mg supplemental calcium and 400 IU vitamin D daily. Whole-body and lumbar spine density increased in both groups; total hip density increased only in the resistance group. Hinton et al., 2015.

The study supports attention to exercise type and skeletal site, but it had no inactive control and gave the same supplements to both groups. It cannot isolate the contributions of time, shared nutrients and exercise, and it did not demonstrate fewer fractures. It also does not justify immediately adding a jumping program to painful or recently increased training.

The relevant concept is a coordinated system: food provides materials and energy, while loading provides a stimulus whose dose, progression and recovery also matter. There is no evidence here that extra pills make any training load tolerable.

What this changes in my routine

I can keep yogurt because I enjoy it and it contributes protein and calcium, while recording any future change in the amount I drink as ayran. Adding water changes concentration and volume; it does not change the total calcium consumed if the same yogurt amount is eventually finished. A smaller yogurt amount, another dairy product or a change in fish needs a fresh food estimate rather than an assumed identical total.

Vitamin D deserves its own decision, using the actual product label and dose rather than treating yogurt as automatically fortified. A plan to buy it is different from a recorded dose taken. The purpose is to address a plausible intake gap, not to promise stronger shoulders or guaranteed injury prevention.

My previously reported progressive shoulder pain is also a separate problem. These studies concern stress fractures, bone density or fracture prevention; none diagnoses the source of front-of-shoulder pain or proves that calcium and vitamin D treat it. Reducing aggravating loading and obtaining appropriate assessment if pain persists or worsens remain distinct from improving the diet.

The most useful next food decision is therefore to verify the yogurt nutrient label, record vitamin D accurately if taken, and keep the meals comfortable enough to eat consistently. Nutrition and training should support each other without turning a positive trial in a different population into an extra supplement requirement.

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