Which supplements for bone health?

Which nutrients influence bone health?

Do calcium and vitamin D form the basic duo?

Together, these minerals maintain the balance needed for skeletal strength, especially after age 50, the period when loss of bone mass accelerates. The adult skeleton contains around 1 kg of calcium, of which 99% is stored in the bones; the remainder circulates in the blood and contributes to muscle contraction and blood clotting. Vitamin D, synthesised by the skin during sun exposure, promotes calcium absorption by the intestine. Without it, even a correct calcium intake remains partly useless. The FOPH notes that in winter, more than 60% of adults show a blood level of 25-hydroxyvitamin D below the recommended threshold of 50 nmol/l^[10]. This vitamin is also involved in maintaining the immune system and in the normal functioning of the body.

Does vitamin K2 have a distinct role?

Vitamin K2 activates two key proteins (osteocalcin and matrix-Gla protein) that direct calcium fixation onto the bones and limit its deposition in the arteries, contributing to the mineralisation of the skeleton. A meta-analysis of 16 trials on 6,425 postmenopausal women (Ma et al., 2022)^[5] confirms an improvement in lumbar spine density with vitamin K2 supplementation. A more recent meta-analysis (Zhang et al., 2025, Frontiers in Endocrinology)^[6] confirms a favourable effect on the biological markers of bone remodelling, but stresses that the direct impact on fracture prevention remains to be confirmed by longer-term trials. Proteins, magnesium and zinc contribute to the bone matrix, but their isolated supplementation has not shown an effect of its own on density in adults without deficiency. Manganese and other trace elements are involved at lower doses in the metabolism of bone tissue.

What effect on density and fracture risk?

Do they really improve bone mineral density?

The effect is real but moderate. A recent meta-analysis of 11 trials on 43,869 postmenopausal women (Cong et al., 2025)^[1] finds a slight but measurable improvement in pelvic density thanks to the calcium + vitamin D combination, with no net gain at the lumbar spine or femoral neck. This improvement corresponds to a slowing of natural resorption rather than a spectacular gain. Another meta-analysis of 13 trials (Bai et al., 2025, Nutrients)^[2] shows that combining supplementation with physical activity — especially whole-body vibration or Baduanjin — markedly increases lumbar spine and femoral neck density in postmenopausal women, and slows mineral loss linked to menopause. The most marked gains appear between 3 and 6 months of combined intervention. Beyond 12 months, the effect plateaus. Regular weight-bearing exercise helps to strengthen the bones and supports bone capital throughout life.

Do they prevent fractures?

Not in the general population without deficiency. The VITAL trial (25,871 healthy adults, LeBoff et al., New England Journal of Medicine, 2022)^[4] showed no reduction in total, non-vertebral or hip fractures with 2,000 IU daily of vitamin D alone, regardless of baseline status. In institutionalised and deficient older adults, however, the calcium + vitamin D combination remains useful for preserving the skeleton: a meta-analysis of 19 trials on 69,234 older subjects (Jiao and Jiang, 2024)^[3] shows a reduction in the number of fractures, an increase in mineral density and a normalisation of the blood level of 25-hydroxyvitamin D. The benefit therefore depends heavily on baseline nutritional status: an adult with sufficient intake will gain practically nothing from taking an additional supplement. Lifestyle — regular physical activity, stable body weight, balanced diet — weighs more than supplementation alone.

Which doses to choose according to Swiss recommendations?

What do the FOPH, the FSVO and the SVGO recommend?

The FOPH and the FSVO recommend 600 IU of vitamin D for children and adolescents, and 800 IU from age 60^[10]. The Swiss Association against Osteoporosis (SVGO/ASCO), in its 2025 recommendations, targets an intake of 1,000 to 1,200 mg of calcium and 800 IU of vitamin D for people at risk of osteoporosis^[11]. These thresholds aim at a serum level of 25-hydroxyvitamin D above 50 nmol/l, considered sufficient to preserve the skeleton. Intake is preferably taken with a meal containing fats, which improves absorption — the dosage form matters less than this timing: capsule, tablet or softgel give equivalent results at the same dose. For calcium, the priority remains diet: a plain yoghurt provides around 150 mg, a glass of milk 250 mg, a 30 g piece of gruyère about 300 mg. Lactose-intolerant people will turn to fortified plant-based drinks, sardines with bones or certain mineral waters.

How to meet needs through diet first?

Two to three servings of dairy products supply about 1,000 mg of calcium; 20 minutes of sun exposure (face and arms) in summer covers vitamin D needs for an adult. For proteins, the recommendation targets 0.8 g per kilo of body weight per day in adulthood, and 1 to 1.2 g/kg after age 65, according to the European recommendations coordinated by Geneva University Hospitals (Chevalley et al., ESCEO 2022)^[9]. A rich and varied diet forms the foundation of a strong skeleton: calcium-rich foods such as canned sardines with bones, tofu fortified with calcium sulphate, certain Swiss and French mineral waters (above 300 mg/l) and almonds round out intake. Leafy green vegetables such as kale, as well as fresh seasonal fruits, provide magnesium and complementary vitamins. In winter, the skin no longer synthesises enough vitamin D: supplementation or fortified foods make up this seasonal shortfall, particularly for older people, women who cover their hair and dark-skinned subjects.

What precautions before supplementing?

What risks in case of overdose?

Overdose of vitamin D leads to hypercalcaemia (excess calcium in the blood) and a danger of kidney stones; excess calcium increases constipation and, according to several observational studies, may weigh on cardiovascular health. The upper tolerable limit is set at 4,000 IU daily for vitamin D and 2,500 mg for calcium in adults, according to the European Food Safety Authority (EFSA)^[12]. Beyond that, the benefit-risk balance is reversed. A meta-analysis of 14 trials on 985 kidney transplant recipients (Cai et al., 2025)^[7] reports that supplementation increases the danger of hypercalcaemia without a clear benefit on overall skeletal density or fracture prevention. For any prolonged intake, an annual blood test for 25-hydroxyvitamin D and serum calcium remains essential to avoid this kind of problem. The quality of the product chosen, its origin and the declaration of doses on the label help to make daily intake safer.

Should supplements be distinguished from medical treatment?

Yes, formally. Food supplements cover nutritional needs but do not treat established osteoporosis. A skeletal fragility confirmed by bone densitometry (T-score below -2.5) requires specific drug management — bisphosphonates, denosumab, raloxifene or teriparatide — prescribed after assessment. A network meta-analysis of 17 trials on 6,932 patients treated for breast cancer (Xu et al., 2026, Frontiers in Oncology)^[8] shows that all active drugs clearly outperform calcium + vitamin D alone for preventing mineral loss. In practice, the supplement accompanies the medicine but never replaces it; formulas aimed at strengthening joints or relieving joint pain also do not act on the deep fragility of the skeleton. A medical consultation is required after a low-energy fall followed by a fracture, in cases of persistent joint or bone pain, or where aggravating factors are present (prolonged corticosteroid therapy, early menopause, family history, rheumatoid arthritis). It is best to consult a healthcare professional before starting any course.

Frequently asked questions on supplements and bone health