Calcium
Calcium carbonate / calcium citrate · Foundation
Essential for bone, best obtained from food, and the supplement form carries a cardiovascular question the food form does not.
What the evidence says
Essentiality is not in question — but that is not the same as evidence for routine supplementation, which is where the tier sits. Fracture findings are mixed and population-dependent: benefit appeared most clearly with vitamin D in deficient or institutionalised older adults, and much less clearly in people already meeting their needs through diet. Several analyses raised a possible increase in cardiovascular events and kidney stones from supplements specifically — a signal not seen with dietary calcium.
What studies used
Recommended intakes sit around 1,000–1,200 mg/day TOTAL from food plus supplements combined. Carbonate was dosed with food in trials because it needs stomach acid; citrate does not.
Reported from published studies and product labelling — a record of what was used in research, not a recommendation. What is right for you is a conversation with a clinician.
Watch out for
- Count dietary intake first — most people are closer to target than they think
- Competes with iron and zinc for absorption, so taking everything together undercuts all three
Evidence base
established literature
Large human evidence base: several phase 3 or 4 trial reports, plus multiple meta-analyses or systematic reviews.
This letter measures how much human research exists, not whether it works for you — the tier above (Moderate) is the read on quality.
Research (12)
- Calcium intake and bone mineral density: systematic review and meta-analysisBMJ · 2015
- Calcium and vitamin D in bone fracture healing and post-traumatic bone turnoverEur Cell Mater · 2018
- Nutrition and Osteoporosis PreventionCurr Osteoporos Rep · 2024
- Osteoporosis prevention, diagnosis, and therapyJAMA · 2001
- Calcium Supplementation- Efficacy and SafetyCurr Osteoporos Rep · 2025
- Stress fracturesArch Endocrinol Metab · 2022
- Supplementation of vitamin D isolated or calcium-associated with bone remodeling and fracture risk in postmenopausal women without osteoporosis: A systematic review of randomized clinical trialsNutrition · 2023
- The effects of caffeine on bone mineral density and fracture riskOsteoporos Int · 2022
- Association Between Calcium or Vitamin D Supplementation and Fracture Incidence in Community-Dwelling Older Adults: A Systematic Review and Meta-analysisJAMA · 2017
- Use of calcium or calcium in combination with vitamin D supplementation to prevent fractures and bone loss in people aged 50 years and older: a meta-analysisLancet · 2007
- The effect of vitamin D on bone and osteoporosisBest Pract Res Clin Endocrinol Metab · 2011
- What is the impact of daily oral supplementation of vitamin D3 (cholecalciferol) plus calcium on the incidence of hip fracture in older people? A systematic review and meta-analysisInt J Older People Nurs · 2023
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