Do women need vitamin D and calcium for bone health?

How much calcium?

Calcium is the main mineral in bone. US recommended dietary allowances (NIH Office of Dietary Supplements) are:

Food first: dairy, calcium-set tofu, sardines or pilchards with bones, fortified products and some greens. If your food supplies about 600 mg, the gap to 1 000 mg is roughly 400 mg, so a modest supplement (or a few more dairy or fortified servings) is enough; taking more than you need adds risk without proven benefit. Evidence on calcium supplements is mixed: some meta-analyses suggest a small cardiovascular signal, others do not, and kidney stone findings conflict. Intakes at or below the upper limit are considered acceptable.

How much vitamin D?

Vitamin D helps absorb calcium and supports muscle and bone. Recommended intake for healthy adults is 600 to 800 IU (15 to 20 µg) a day. The EFSA (2023) upper limit is 4 000 IU (100 µg) a day for adults. The Endocrine Society (2024) does not recommend routine testing or higher supplementation for healthy adults under 75. Supplements help people who are deficient; they do not boost performance if levels are adequate.

South Africa is sunny, but low vitamin D is still found: a 2024 study of 1 244 Eastern Cape healthcare workers found 28.5% below 50 nmol/L, while a Western Cape study of healthy young adults (2019) reported low deficiency prevalence. Indoor workers, covered clothing, darker skin and older age raise risk. See do South Africans need vitamin D in summer and how much vitamin D.

Do supplements prevent fractures?

Evidence is mixed. The US Preventive Services Task Force concluded with moderate certainty that daily doses below 1 000 mg calcium and 400 IU vitamin D do not prevent fractures in postmenopausal women, and evidence for larger doses is inadequate. Some trials found calcium plus vitamin D reduced fractures in frail or institutionalised older people. The strongest levers for bone after menopause are resistance and impact training, enough protein, not smoking, limited alcohol, and medical treatment where indicated.

What do supplements cost in South Africa?

Vitamin D3 at 1 000 IU, October 2026: New Leaf D3 and K2, 183 tablets, R395 (R2.16 a day, Faithful to Nature); Now Foods D3 and K2, 120 capsules, R276.75 special (R2.31); Dis-Chem Gold Vitamin D3 1000 IU, 60 tablets, R160 (R2.67, Dis-Chem Living Fit). A 1 000 IU dose is above the 600 to 800 IU intake target but well below the 4 000 IU upper limit. We did not capture calcium prices. See best vitamin D3 in South Africa.

What about collagen, protein and creatine?

Collagen has a single 12-month trial of 5 g a day in postmenopausal women with reduced bone density, partly manufacturer-funded (details). Protein supports bone and muscle (how much protein women need). Creatine has emerging evidence (creatine in perimenopause).

When to see a doctor

Ask for a bone density (DXA) scan and advice if you are postmenopausal with risk factors, have had a fracture, lost height, use long-term corticosteroids, or have kidney disease, hyperparathyroidism or a thiazide diuretic prescription (these change calcium and vitamin D safety). Do not stop prescribed osteoporosis treatment in favour of supplements. Pregnant or breastfeeding women and under-18s should follow their doctor's or clinic's advice on vitamin D and calcium.

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