Why Did I Break a Bone? Hormones, Genetics & Vitamin D Explained

The question behind the question

When a relatively minor fall causes a fracture, doctors call it a fragility fracture. It's a clinical signal — your bones don't have the strength they should. And it's the most important warning sign you'll ever get about your bone health, because the single biggest predictor of a future fracture is having had one already.

Don't panic, but don't shrug it off either. Treat it as information. Your body is asking for the kind of attention it hasn't needed before — and most of what helps is within your reach.

Why women's bones change with menopause

Bone is a living tissue. Your body is constantly breaking down old bone (a process called resorption) and building new bone (called formation). Through your twenties and thirties, these two processes stay roughly balanced — your bone density remains stable.

Estrogen is the hormone that keeps that balance tilted slightly in favour of bone formation. As the Endocrine Society explains, estrogen acts directly on the cells that build bone (osteoblasts) and the cells that break it down (osteoclasts), holding the whole system in check.

When estrogen drops in perimenopause and menopause, that protection falls away. The cells breaking down bone become more active; the cells building bone become less so. The result, according to Cleveland Clinic: women lose 1–2% of their bone density per year through the menopausal transition, sometimes as much as 3–5%. Cumulatively, women can lose up to 20% of their lifetime bone density during menopause itself.

That's why a fall that wouldn't have caused a fracture at 35 produces one at 55. The fall is the trigger, but the fragile bones are the underlying setup.

Vitamin D — why it matters more than most people realize

Calcium gets all the press, but you can take all the calcium in the world and it won't reach your bones if you don't have enough vitamin D. Vitamin D is the hormone (yes, technically a hormone, not just a vitamin) that allows your gut to absorb calcium and your body to put it where it belongs: in your bones.

Conventional bone-health guidelines from bodies like the International Osteoporosis Foundation recommend a baseline of 800–1,000 IU per day to prevent overt deficiency. In functional medicine, the dosing target is higher — typically 4,000 IU of vitamin D3 per day for postmenopausal women, with the goal of bringing blood 25-hydroxy-vitamin-D levels into the optimal window of 30–60 ng/mL (75–150 nmol/L). The conventional 800 IU is enough to avoid clinical deficiency; 4,000 IU is the dose that actually puts most women into the range associated with the strongest bone-protective benefit.

Vitamin D doesn't work alone, though. To actually deliver calcium into bone and avoid depositing it where it shouldn't go (your arteries, your kidneys), vitamin D needs vitamin K2 as a co-factor. Always pair vitamin D supplementation with vitamin K2 — without K2, the calcium your vitamin D mobilizes can end up in the wrong places. K2 is also what helps your body actually absorb and direct the vitamin D you're taking. The two work as a team.

If you live in Canada, plan for the latitude

Living anywhere north of about the 40th parallel — which includes all of Oakville, the GTA, and essentially every Canadian city — creates a real seasonal vitamin D problem. From late September through April, the sun's angle here is too low for your skin to synthesize meaningful vitamin D from sunlight, regardless of how much time you spend outdoors.

Practical translation: start supplementing vitamin D every day from September onwards, and continue through the winter and spring. Even women who feel like they got plenty of sun over the summer are typically running a vitamin D deficit by November. By February, blood levels are often well into the deficient range without anyone realizing it.

And critically: get your blood level checked regularly. Once a year is a reasonable minimum for most women; twice a year (end of summer and end of winter) is better, especially if you have a known genetic predisposition to lower vitamin D levels — which a surprising number of women do, as we're about to discuss.

The genetics: why we don't all respond the same

Here's where it gets interesting — and where standard one-size-fits-all advice often breaks down.

Vitamin D works by binding to a receptor (the vitamin D receptor, or VDR) on your cells. The instructions for building that receptor are encoded by the VDR gene on chromosome 12. And like most genes, the VDR gene comes in different versions — what geneticists call polymorphisms. There are over 900 known variants in the VDR gene alone.

Why does this matter? Because a systematic review and meta-analysis of VDR polymorphisms and vitamin D supplementation response found that different VDR variants respond differently to the same vitamin D dose. The four most-studied polymorphisms are called FokI, BsmI, ApaI, and TaqI. Women with certain TaqI variants and the FokI “FF” genotype tend to respond better to standard vitamin D supplementation. Others may need higher doses to achieve the same bone-density benefit, or may need different supporting nutrients (vitamin K2, magnesium, boron) to make their vitamin D actually work.

The clinical takeaway: if you're taking the “standard dose” of vitamin D and your blood level still won't come up — or if your bone density keeps dropping despite doing everything right — your VDR genetics may be a piece of the puzzle. VDR gene testing is available through functional-medicine and some endocrinology labs, and the result can guide a more personalized protocol.

Genetics also influence how strongly your body experiences menopausal symptoms in the first place. Some women glide through the transition with mild symptoms; others have profound vasomotor and bone-density consequences. That difference is partly inherited. It's why “my mother breezed through it, so I will too” is one of the most misleading assumptions in women's health.

Practical supplements — what genuinely helps

A reasonable starting protocol for most postmenopausal women, adjusted based on lab work and your specific risk profile:

• Vitamin D3 — 4,000 IU daily as a functional-medicine baseline for postmenopausal women, adjusted based on blood 25(OH)D testing to keep your level between 30 and 60 ng/mL. Higher doses sometimes needed initially to correct deficiency, then tapered to maintenance.
• Vitamin K2 (MK-7) — 90–180 mcg daily. Pair this with your D3 — K2 directs calcium into bone (rather than into arteries) and helps your body actually use the vitamin D you're taking. Most over-the-counter vitamin D supplements don't include K2; consider adding it as a separate supplement or buying a combined D3/K2 product.
• Magnesium — 200–400 mg daily. Magnesium is required for vitamin D activation and bone formation. Up to 50% of adults are mildly magnesium-deficient. Glycinate or citrate forms are well-tolerated.
• Protein — 1.0–1.2 g per kg of bodyweight daily. Bones need protein, not just minerals. Many postmenopausal women are unintentionally under-eating protein.

⚠ A note on calcium: Calcium supplementation is not something to start on your own. Over-supplementing calcium can contribute to kidney stones and, in some patients, to cardiovascular calcification. Many women already get enough calcium from diet alone, and adding a calcium supplement on top can do more harm than good. Always discuss calcium supplementation with your doctor first, and ideally only after a blood-work and dietary assessment to determine whether you actually need it and at what dose.

This is a starting point, not a prescription. Specific doses depend on your blood work, kidney function, current medications and risk profile. Always discuss new supplements with your physician, particularly if you have any history of kidney stones, cardiovascular disease or are on medications that interact with vitamin D, K2 or magnesium.

Rebounder — gentle bone loading you can do at home

Bones respond to load. Without mechanical stress, they thin. With the right kind of stress, they remodel and strengthen. The question for women in their 50s and 60s isn't whether to load their bones — it's how to do it safely.

A rebounder (a small home mini-trampoline) is one of the gentlest ways to deliver bone-loading impact without hammering arthritic joints. Each gentle bounce produces ground reaction forces measurable enough to signal your bones, but the soft mat absorbs the punishment. Combined with the balance work rebounding requires — your stabilizing muscles fire constantly to keep you upright — it becomes one of the most efficient bone-and-balance combo exercises you can do.

What the research shows: a 12-week mini-trampoline trial in older women with osteopenia produced significant improvements in balance, gait, and fear of falling — all of which are huge for fracture prevention. Some smaller studies have also shown lumbar spine bone-density improvements with consistent rebounding (around 20 minutes, 3 times per week). The bone-density evidence isn't as strong as for some other interventions, but the fall-prevention evidence is very strong — and most fragility fractures happen because of a fall, not because of bone density alone.

Practical starter routine:

• 3 sessions per week, 15–20 minutes each
• Start with gentle bounces — feet stay on the mat — for the first 5 minutes
• Progress to small jogs, side-to-side steps, light arm movements
• If you've had a recent fracture or have severe osteoporosis, get cleared by your physician first

Whole-body vibration plates — passive but promising

Whole-body vibration (WBV) is exactly what it sounds like: you stand on a vibrating platform that delivers small, rapid mechanical oscillations through your whole body. The bones perceive these oscillations as repeated micro-loading, which can stimulate bone remodeling.

The evidence is genuinely mixed but trending positive. A 2022 systematic review and meta-analysis of randomized controlled trials concluded that WBV had measurable effects on bone density in postmenopausal women, particularly with high-frequency (~30 Hz), low-magnitude (~0.3 g), high-cumulative-dose (~7,000 cumulative minutes) protocols. Other large trials have shown no effect. The honest answer: WBV likely helps modestly, particularly for lumbar spine density, when done consistently over months — and the side benefits for muscle strength, postural control and circulation are well-established.

Practical starter routine:

• 10–15 minutes per session, 3–5 sessions per week
• Start at lower frequencies (15–20 Hz) and lower amplitudes; progress over weeks
• Stand with knees slightly bent — this transmits vibration through to bones rather than absorbing it in soft tissue
• If you have implanted hardware, retinal disease, severe osteoporosis or are pregnant, get cleared first

Other lifestyle moves that genuinely matter

• Resistance training, 2–3 times per week. Heavy(ish) weight-bearing exercise is the single best evidence-based intervention for bone density. Bodyweight, dumbbells, kettlebells, machines — any of them. Don't fear the weights.
• Daily walking, ideally outdoors. Combines weight- bearing impact with sunlight (vitamin D), and the daily routine builds the resilience to fall less often in the first place.
• Balance work. Single-leg standing, tai chi, yoga. The single best fracture-prevention intervention isn't bone density — it's not falling. Build the balance system and you reduce fracture risk dramatically.
• Eliminate or reduce smoking and heavy alcohol. Both directly thin bone.
• Sleep. Bone remodeling happens at night. Chronic poor sleep impairs the cycle.
• Address gut health. If you can't absorb calcium and vitamin D well, no supplement plan will reach its potential. Dysbiosis, low stomach acid, and inflammatory bowel conditions can all impair absorption.

Get tested — what to actually ask for

If you've had a fragility fracture or you're entering the menopausal transition, the workup I'd recommend includes:

• DEXA bone density scan — the gold-standard measurement of bone mineral density. Often covered by OHIP for eligible patients.
• 25-hydroxy vitamin D level — your circulating vitamin D status. Aim for 30–60 ng/mL.
• Calcium, magnesium, phosphorus, parathyroid hormone (PTH) — the supporting cast for bone health.
• Thyroid panel (TSH, free T4) — overactive thyroid accelerates bone loss.
• Estradiol (and FSH/LH) if you're assessing menopausal status.
• Bone turnover markers (CTX, P1NP) — for patients on bone treatment to monitor response.
• Optional: VDR genetic testing — for women whose vitamin D levels won't come up, who've had unexplained rapid bone loss, or who want a personalized protocol.

The bigger picture — and what to do next

The reason you broke a bone wasn't bad luck and it isn't your fault. It's a signal that your bone biology is changing — often quietly, often years before the first fracture, and almost always in a direction that responds well to attention.

Most women aren't given a clear path to act on this. They leave their doctor's office with a vague directive to “take more calcium and vitamin D” and no specifics. If that's where you are, you can do better. The combination of appropriate supplementation, consistent loading exercise (resistance training, rebounder, vibration plate), balance work, and the right labs to track your response gives you a real path forward.

At Oakville Pain Clinic I see many women in their 40s, 50s and 60s for musculoskeletal pain — and what often becomes clear in the assessment is that their pain story and their bone-health story are connected. If you'd like a comprehensive functional-medicine-informed look at your bone health risk, your hormone status, your vitamin D and the lifestyle program that actually fits your life, book a consultation. We'll order the right labs, review your imaging, and build a personalized plan.

— Dr. Biljana Kostovic