Calcium: the supplement question that experts still disagree about

Calcium is an odd case. The mineral itself is uncontroversial. Calcium supplements are one of the few places where two credible expert bodies read the same evidence and came away with different conclusions.

What it does in the body

• Calcium forms most of the structure of bones and teeth, and a small ionised pool controls blood vessel contraction, muscle function, clotting, nerve transmission and hormone secretion. Evidence E source

How much you need

• The RDA for calcium is 1,000 mg a day for adults 19–50 and men 51–70, and 1,200 mg for women 51+ and all adults 71+. — adults Evidence E source
• The Tolerable Upper Intake Level for calcium is 2,500 mg a day at ages 19–50 and 2,000 mg from 51. — adults Evidence E source
• The calcium requirement for babies is calculated from balance studies: infants retain about 40 per cent of the calcium they take in, and 240 to 400 mg a day gives the best absorption with the least waste. — healthy children aged 0 to 4 years; 23 studies, 15 mass balance and 8 isotopic, with only 3 studies in children older than six months Evidence C source
• Five weeks on roughly half the recommended calcium left no trace at all: parathyroid hormone, blood calcium and every measured metabolite stayed where they were. — healthy Chinese adults aged 23 to 28, half men and half women, with a habitual intake near the Chinese average of 400 mg a day against a recommended 800 mg Evidence B source
• Four out of five plant-based milks on the shelf are fortified with calcium, which means one in five is not, and the carton is the only way to tell. — 129 plant-based milk products sold in Illawarra supermarkets, Australia: almond, oat and soy made up 82% Evidence C source
• How much calcium a plant milk holds is a moving target: the share of Australian plant milks fortified with calcium went from 42.6% in 2020 to about 80% within four years. — plant-based milks on sale in Australia, audited in 2020, 2021 and again for this study Evidence C source
• Taken as a group, plant milks matched cow's milk for calcium, unlike protein, iodine and B12, where they fell well short. — 129 plant-based milk products against cow's milk, fortified and unfortified products pooled in the analysis Evidence C source
• Even breast milk, the most studied food there is, has no single calcium number: the pooled mean is 261 mg/L, but individual studies ran from 2 to 686 mg/L. — 154 studies of apparently healthy mothers across six continents, published 1965-2022 Evidence C source
• In the American diet calcium does not arrive as 'dairy' so much as in pieces: about 37% from milk and dairy, and another 17% hidden in pizza, sandwiches and pasta dishes. — US population, What We Eat In America / NHANES 2009-2010 Evidence E source
• Where dairy is scarce, drinking water is a real calcium source: in Madagascar it supplied about a fifth of all the calcium adolescents and women got. — young children, adolescents and women of reproductive age across all 23 regions of Madagascar, 2024 National Micronutrient Survey Evidence C source

How well your body absorbs it

• About 45% of calcium is absorbed at intakes of 200 mg a day but only about 15% above 2,000 mg a day. — adults Evidence E source
• Calcium supplements are absorbed best in doses of 500 mg or less: about 36% of a 300 mg dose against 28% of a 1,000 mg dose. — adults Evidence E source
• Only about 5% of the calcium in spinach is absorbed, against about 27% of the calcium in milk, because oxalic and phytic acid bind it. Evidence E source
• Parathyroid hormone is the one marker that moves: adding calcium to food pushed it down and nudged children's height and hip bone density up. — mostly women and children aged 1 to 72 months; calcium intake rose by 460 mg in children and up to 1,200 mg in postmenopausal women Evidence A source
• A year of daily milk in young children lowered parathyroid hormone by 13 per cent and built measurably more bone in the forearm, but not in the legs. — children aged 4 to 6 in northwest China for the trial; children aged 3 to 18 in the pooled trials Evidence A source
• Preparation decides how much of a tortilla's calcium you get: cutting the phytate in the maize by about 60% lifted absorption from 35% to 50% of the dose. — 5 healthy adult women fed roughly 140 g of tortillas in place of breakfast, once from low-phytate maize and once from the matching wild-type isohybrid Evidence C source
• Calcium-rich mineral water is absorbed at least as well as calcium from dairy, on the small evidence that exists. — adults in four studies that compared calcium absorption from mineral water with absorption from dairy products, Medline 1966-1998 Evidence C source

What too little does

• Long-term calcium shortage weakens bone and leads to osteoporosis, which means fragile bones and a higher chance of a fracture from a fall. — adults with chronically low calcium intake Evidence E source
• Chronic calcium deficiency also causes osteomalacia, where bone fails to mineralise properly and softens, in adults and in children. — adults and children with chronic deficiency Evidence E source
• How much calcium older adults eat does not predict how fast they lose bone: in roughly seven out of ten cohort studies there was no association at all. — adults over 50; 23 cohort studies of women and 7 of men, with mean calcium intake above 500 mg a day in all but one Evidence C source
• Broken bones are not a sign of eating too little calcium: across 44 cohort studies, how much calcium people ate did not track with how often they fractured. — adults over 50 Evidence C source

Who is most likely to fall short

• Teaching dialysis patients how to prepare food, on top of ordinary dietary advice, kept their blood calcium better controlled over a year than the advice alone. — 47 haemodialysis patients, all on individualised phosphate binder therapy Evidence B source

What the evidence does and does not show

• Not all trials find that calcium supplements improve bone health or reduce fractures, and more research is needed before conclusions can be drawn. — older adults Evidence B source
• A meta-analysis of 14 randomised trials in 28,935 healthy postmenopausal women found calcium supplements of 500–2,000 mg a day raised cardiovascular disease risk by 15%. — healthy postmenopausal women Evidence A source
• An expert panel concluded on moderate-quality evidence that calcium from food or supplements neither increases nor decreases cardiovascular risk. — general adults Evidence E source
• Twenty-two years after the Women's Health Initiative gave 36,282 women calcium with vitamin D, cancer deaths were 7 per cent lower and cardiovascular deaths 6 per cent higher, with no change in deaths overall. — postmenopausal women in the United States with no history of breast or colorectal cancer Evidence B source
• A meta-analysis of 13 double-blind placebo-controlled trials found calcium supplements raised cardiovascular risk by about 15 per cent in healthy postmenopausal women. — mostly healthy postmenopausal women Evidence A source
• A second meta-analysis, of 12 randomised trials, found no link between calcium supplements and heart attacks, strokes, heart failure or death. — participants of 12 randomised trials of calcium supplementation Evidence A source
• Across 35 prospective cohorts with 163,657 deaths, calcium from food tracked with slightly lower mortality while calcium from supplements tracked with nothing at all. — adults followed for 4.2 to 28 years in 36 publications Evidence C source
• The largest review to date, 69 trials and 153,902 people, found little to no effect of calcium supplements on the risk of breaking a bone. — adults aged 18 and over, 87 per cent community dwelling and 73 per cent not at high risk of fracture or falls Evidence A source
• That 'no benefit' verdict rests on people who were mostly healthy and living at home: for those at high risk or in residential care the same review says the evidence is thin. — the 69 included trials, characterised by living situation and baseline fracture risk Evidence A source
• In older people living at home, neither calcium nor vitamin D nor the two together lowered the risk of a hip fracture. — community-dwelling adults older than 50 years in 33 randomised trials Evidence A source
• An earlier meta-analysis that also counted people in care homes reached the opposite conclusion: calcium with vitamin D cut hip fractures by 30 per cent. — middle-aged to older adults, both community-dwelling and institutionalised, in eight randomised trials Evidence A source
• In postmenopausal women who already have osteoporosis, calcium with vitamin D moved bone density only at the pelvis and did not reduce fractures at all. — postmenopausal women with diagnosed osteoporosis in eleven randomised trials Evidence A source
• The 2025 Cochrane update found calcium in pregnancy makes little to no difference to pre-eclampsia, and once the small trials are set aside that null result carries high certainty. — pregnant women; 10 randomised trials in the updated review, 6 reporting pre-eclampsia Evidence A source
• That reversal happened because the reviewers threw out 20 trials they had previously counted, nine of them over doubts about whether the data were real. — the review's own included and excluded trial set: 10 trials retained, 8 comparing calcium with placebo and 2 comparing low with high dose Evidence A source
• Starting calcium before conception, in women whose last pregnancy had pre-eclampsia, also failed to prevent it. — 1,355 parous women whose most recent planned pregnancy had been complicated by pre-eclampsia or eclampsia, in one multicentre double-blind placebo-controlled trial Evidence A source
• In people whose blood pressure is normal, calcium supplements lower systolic pressure by 1.37 mmHg, an effect that is certain and tiny at the same time. — normotensive adults; 20 trials included, 18 in the meta-analysis Evidence A source
• The 'alkaline diet' story, that protein and grains acidify you and pull calcium out of your bones, does not survive the balance studies it rests on. — healthy adults whose acid-base intake was deliberately manipulated, 5 of 16 candidate studies met the inclusion criteria Evidence A source
• More calcium in the urine does not mean calcium leaving the body: the two moved independently in every study that measured both properly. — healthy adults in controlled acid-base feeding studies Evidence A source
• Drinking more milk did not mean fewer broken bones: in two large Swedish cohorts fracture risk edged up, not down, with every extra glass in women. — 61,433 Swedish women followed 20 years and 45,339 Swedish men followed 11 years Evidence C source
• When these studies say 'a glass of milk' they mean a measured 200 mL, so 'three or more glasses a day' is at least 600 mL, worth knowing before applying the finding to your own mug. — 61,433 Swedish women and 45,339 Swedish men Evidence C source
• Nobody has ever run a randomised trial of milk drinking against death or fracture, so every claim in either direction rests on people who chose what to drink. — the whole literature on milk intake, mortality and fracture Evidence C source
• The tidy figure for calcium in breast milk is an average over studies that disagree almost completely with one another. — 154 breast-milk calcium studies pooled by random effects Evidence C source

What too much does

• The upper limit for calcium is based on evidence linking 1,000 mg a day of supplemental calcium over seven years with a greater risk of kidney stones. — postmenopausal women in the WHI Evidence C source
• For the quarter of Americans who take a calcium supplement, the pill is not a rounding error: it averages 521 mg a day on top of food. — US individuals aged 2 and over, excluding pregnant and lactating women and breast-fed children, WWEIA/NHANES 2009-2010 Evidence E source

Medicines it interacts with

• Calcium carbonate can interfere with levothyroxine absorption, and the FDA label says not to take them within 4 hours of each other. — people taking levothyroxine Evidence E source
• Taking calcium supplements at the same time as quinolone antibiotics reduces how much of the antibiotic is absorbed. — people taking ciprofloxacin, gemifloxacin or moxifloxacin Evidence E source

What to do with this

Food first, and not because supplements are wicked. Food arrives in small doses across the day, which is how calcium is absorbed best, and it brings protein and other minerals with it.

Not all milligrams are equal. Dairy, fortified drinks and tinned fish with the bones in hand over most of what they promise. Spinach hands over very little, because oxalate holds on to it. Kale and other low-oxalate greens sit somewhere in between.

If you do take a supplement, split it into doses of 500 mg or less and keep calcium carbonate four hours away from levothyroxine. Be aware, too, that this is the one area of the site where two credible expert bodies read the same trials and disagreed about heart risk. That is a question to put to your own doctor rather than to a table of numbers.

If you are buying calcium for your bones, know what the trials found. Across 69 of them in 153,902 people, supplements made little to no difference to fractures in adults who were mostly healthy and living at home. For people who are frail or in care the picture is different and much thinner, and that is a question for a clinician who knows your own fracture risk.

If you are pregnant, ask rather than assume. The recommendation to take calcium against pre-eclampsia rested on a body of trials that has just been cut down by twenty, nine of them over doubts about whether the data were real, and what is left shows little to no effect at high certainty. Take that to your midwife or doctor. It is not a reason to stop something you were prescribed for a reason we cannot see from here.

If dairy is out, the carton is where this is won or lost. In an audit of 129 plant milks, 80.6 per cent carried added calcium, and as a group they matched cow's milk for it while falling short on protein, iodine and B12. The other fifth had none, and an unfortified almond or rice drink has almost none of its own. Read the nutrition panel once per brand and then stop thinking about it.

Do not let anyone sell you an alkaline diet for your bones. Eating more protein does put more calcium in your urine, and that is where the story starts and ends. In the controlled balance studies, whole-body calcium balance did not change with acid load and neither did a marker of bone breakdown.

Where to get it from food

The bottom line

Getting calcium from food is not in dispute. Supplements are, and the honest summary is that the effect on fractures is inconsistent and the effect on heart risk is contested. If you do take them, the size of each dose matters more than the total. Your body absorbs a 300 mg dose far more efficiently than a 1,000 mg one, so two small doses beat one large one. Two of these answers have moved since the page was written, and both moved the same way. The largest review of calcium supplements and fractures now covers 69 trials and 153,902 people, and it found little to no effect on breaking a bone. An earlier meta-analysis that also counted people in care homes had found a 30 per cent cut in hip fractures. The gap between those two is mostly a gap between who was in them, because the newer pool is largely people living at home who were not at high risk, and its authors say outright that for the frail end the evidence is thin. In pregnancy the change is sharper. The 2025 Cochrane update found calcium makes little to no difference to pre-eclampsia, with high certainty, after the reviewers removed 20 trials they had previously counted, nine of them over doubts about whether the data were real. Starting before conception did not work either. If you were told to take calcium in pregnancy, that instruction is older than the evidence under it, and it belongs in a conversation with whoever is looking after you. Three things have been added under this page since it was written, and one of them changes how you should read the rest. Milk is not the settled safe side of the argument. In two Swedish cohorts, 61,433 women followed for twenty years and 45,339 men for eleven, each extra glass a day went with slightly more fractures in women, a hazard ratio of 1.02 for any fracture and 1.09 for the hip, with men on no effect. A glass there is a measured 200 mL. Those are observations of people who chose what to drink, and no randomised trial of milk against fractures has ever been run, which is the honest limit on every claim about milk in either direction. Second, the alkaline diet argument is over: pooled balance studies show urinary calcium rising with the acid load of the diet while whole-body calcium balance and a marker of bone breakdown do not move. Third, if you drink plant milk, check the carton. Four cartons in five are fortified with calcium and the fifth is not, and the share has been climbing fast enough that a brand you checked two years ago tells you nothing about the one in your hand.

Sources

1. ca-01 · Position of an expert body · expert body statement
   Calcium makes up much of the structure of bones and teeth and allows normal bodily movement by keeping tissue rigid, strong, and flexible.
   NIH Office of Dietary Supplements, Health Professional Fact Sheet: Calcium · checked 2026-09-15 · extracted
2. ca-02 · Position of an expert body · expert body recommendation
   Ages 19–50: 1,000 mg; Men 51–70: 1,000 mg; Women 51+: 1,200 mg; Adults 71+: 1,200 mg (value from the source's table, not a sentence)
   NIH Office of Dietary Supplements, Health Professional Fact Sheet: Calcium · checked 2026-09-15 · independently re-checked
3. ca-03 · Position of an expert body · expert body recommendation
   Ages 19–50: 2,500 mg; Ages 51–70: 2,000 mg; Ages >70: 2,000 mg (value from the source's table, not a sentence)
   NIH Office of Dietary Supplements, Health Professional Fact Sheet: Calcium · checked 2026-09-15 · extracted
4. ca-r3-05 · Observational data · systematic review of balance and isotope studies
   The random-effects model meta-regression on 42 mass balance study arms showed an average net calcium retention of 40.4% among infants aged 0-6 mo (β = 0.404 [95% CI: 0.302, 0.506]). Isotope studies suggested calcium intake of 240 to 400 mg/d may promote optimal calcium absorption with minimal loss, and intake from human milk may lead to greater absorption and retention efficacy than formula or solid foods.
   Advances in Nutrition, 2022 · checked 2026-09-17 · independently re-checked
5. ca-s1 · Randomised controlled trial(s) · randomised controlled trial
   The results showed that there were no significant differences in blood and urine metabolites, metabolic hormone [parathyroid hormone, 1, 25(OH)2D3] levels and biochemical indicators(serum Ca, serum P, glycolipid metabolism and hepatorenal function indicators)between the calcium supplementation group and control group at each time point throughout the trail (P>0.05).
   Zhonghua Yu Fang Yi Xue Za Zhi, 2021 · checked 2026-09-17 · independently re-checked
6. ca-c1-01 · Observational data · cross-sectional product audit
   As shown in Table 2, plant‐based milks were most consistently fortified with calcium (80.6% of products). All beverages that were fortified with only a single nutrient were fortified with calcium.
   Hunt et al., Nutrition & Dietetics, 2025 · checked 2026-09-18 · independently re-checked
7. ca-c1-02 · Observational data · cross-sectional product audit
   Our data confirms that there has been a consistent increase in the proportion of plant‐based milks sold in Australia that are fortified with calcium, from 42.6% in 2020 (Zhang et al.) to 79% in 2021.
   Hunt et al., Nutrition & Dietetics, 2025 · checked 2026-09-18 · independently re-checked
8. ca-c1-03 · Observational data · cross-sectional product audit
   All plant‐based milk varieties contained sodium and calcium in levels that were not significantly different to cow's milk.
   Hunt et al., Nutrition & Dietetics, 2025 · checked 2026-09-18 · independently re-checked
9. ca-c1-04 · Observational data · systematic review and meta-analysis of composition studies
   The mean calcium concentration of breast milk was 261 mg/L (95% CI: 238, 284, range: 2, 686).
   Dror & Allen, International Breastfeeding Journal, 2023 · checked 2026-09-18 · independently re-checked
10. ca-c1-07 · Position of an expert body · national dietary survey
    Milk and dairy products contributed over one-third (37%) to total calcium intake, of which about half (19%) was from plain milk.
    FSRG Dietary Data Briefs, USDA Agricultural Research Service, WWEIA/NHANES 2009-2010 · checked 2026-09-18 · independently re-checked
11. ca-c1-09 · Observational data · cross-sectional national survey
    Overall, the contribution of drinking water was also relatively high in all population groups, with around 19% in adolescents and nonpregnant WRA and around 14% in children, contributing most in nonpregnant WRA with 57 mg/d.
    Nutrients, 2026 · checked 2026-09-18 · independently re-checked
12. ca-04 · Position of an expert body · expert body statement
    Absorption of calcium from food is about 45% at intakes of 200 milligrams (mg)/day but only 15% when intakes are higher than 2,000 mg/day.
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Calcium · checked 2026-09-15 · independently re-checked
13. ca-05 · Position of an expert body · expert body statement
    Absorption from supplements is highest with doses of 500 mg or less. For example, the body absorbs about 36% of a 300 mg calcium dose and 28% of a 1,000 mg dose.
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Calcium · checked 2026-09-15 · extracted
14. ca-06 · Position of an expert body · expert body statement
    Absorption of calcium is only 5% for spinach, whereas it is much higher, at 27%, for milk.
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Calcium · checked 2026-09-15 · independently re-checked
15. ca-s2 · Meta-analysis or systematic review · systematic review and meta-analysis
    Compared to controls, height increased 0.83 cm (95% CI 0.00; 1.65), plasma parathyroid hormone decreased -1.51 pmol/L, (-2.37; -0.65), urine:calcium creatinine ratio decreased -0.05, (-0.07; -0.03), femoral neck and hip bone mineral density increased 0.02 g/cm2 (0.01; 0.04) and 0.03 g/cm2 (0.00; 0.06), respectively.
    Nutrients, 2021 · checked 2026-09-17 · independently re-checked
16. ca-s3 · Meta-analysis or systematic review · cluster-randomised controlled trial with meta-analysis of randomised trials
    Of 278 completed the trial, intention-to-treat analysis revealed significant increases in BMD (4.05% and 7.31%) and BMC (4.69% and 7.34%) in the left forearm at the 6th and 12th months in the milk group compared to controls (P < 0.001)...Additionally, milk supplementation was associated with beneficial changes in bone resorption markers, parathyroid hormone (- 12.70%), insulin-like growth factor 1 (6.69%), and the calcium-to-phosphorus ratio (2.22%) (all P < 0.05). The meta-analysis, encompassing 894 children, indicated that dairy supplementation significantly increased BMD (SMD, 0.629; 95%CI: 0.275, 0.983) and BMC (SMD, 0.616; 95%CI: 0.380, 0.851) (P < 0.05) in the arms, but not in the legs (P > 0.05).
    Archives of Osteoporosis, 2024 · checked 2026-09-17 · independently re-checked
17. ca-c1-05 · Observational data · controlled crossover stable-isotope trial
    Mean fractional absorption of calcium from tortillas prepared from the low-phytate maize (0.50 +/- 0.03) was significantly (P = 0.003) greater than that from tortillas prepared from the control maize (0.35 +/- 0.07).
    Hambidge et al., American Journal of Clinical Nutrition, 2005 · checked 2026-09-18 · independently re-checked
18. ca-c1-10 · Observational data · systematic review and meta-analysis
    A meta-analysis based on published p values indicated calcium absorption from mineral waters was significantly higher (p = 0.03) than that from dairy products.
    Böhmer et al., Osteoporosis International, 2000 · checked 2026-09-18 · independently re-checked
19. ca-12 · Position of an expert body · expert body statement
    Calcium deficiency can reduce bone strength and lead to osteoporosis, which is characterized by fragile bones and an increased risk of falling.
    NIH Office of Dietary Supplements, Calcium - Health Professional Fact Sheet · checked 2026-09-16 · independently re-checked
20. ca-13 · Position of an expert body · expert body statement
    Another effect of chronic calcium deficiency is osteomalacia, or defective bone mineralization and bone softening, which can occur in adults and children.
    NIH Office of Dietary Supplements, Calcium - Health Professional Fact Sheet · checked 2026-09-16 · independently re-checked
21. ca-t6 · Observational data · systematic review of prospective cohort studies
    Most studies found no association between calcium intake and change in BMD in women (71%) or men (71%). Among women, five studies reported high rates (>30% of participants) of hormone treatment or osteoporosis therapy (HT/OT) use; 80% of these studies reported a positive association between calcium intake and change in BMD, compared with 10% of studies in which HT/OT use was low.
    Bristow et al., European Journal of Clinical Nutrition, 2022 · checked 2026-09-17 · independently re-checked
22. ca-s4 · Observational data · systematic review of cohort studies and randomised trials
    For dietary calcium, most studies reported no association between calcium intake and fracture (14/22 for total, 17/21 for hip, 7/8 for vertebral, and 5/7 for forearm fracture). For milk (25/28) and dairy intake (11/13), most studies also reported no associations.
    Bolland et al., BMJ, 2015 · checked 2026-09-17 · independently re-checked
23. ca-c1-06 · Randomised controlled trial(s) · randomised controlled trial
    The intervention group received additional education on specific preparation methods of different foodstuffs and consumed two hospital meals prepared according to these methods during hemodialysis.
    Journal of Nephrology, 2024 · checked 2026-09-18 · independently re-checked
24. ca-07 · Randomised controlled trial(s) · clinical trials cited by expert body
    Not all clinical trials have found that these supplements improve bone health or reduce the risk of fractures in this population.
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Calcium · checked 2026-09-15 · extracted
25. ca-08 · Meta-analysis or systematic review · meta-analysis of randomised trials
    A meta-analysis of 14 RCTs (including one study that administered supplements providing 20 mcg [800 IU] vitamin D per day) in 28,935 healthy postmenopausal women found that calcium supplements providing 500 to 2,000 mg/day calcium for 1 to 7 years increased CVD risk by 15% and coronary heart disease risk by 16%
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Calcium · checked 2026-09-15 · independently re-checked
26. ca-09 · Position of an expert body · expert panel review
    An expert panel convened by the National Osteoporosis Foundation and American Society for Preventive Cardiology determined, on the basis of moderate-quality evidence, that calcium intakes with or without vitamin D from foods or supplements neither increase nor decrease the risk of CVD or CVD mortality.
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Calcium · checked 2026-09-15 · independently re-checked
27. ca-h01 · Randomised controlled trial(s) · randomised controlled trial, long-term follow-up
    For women randomly assigned to CaD versus placebo, a 7% reduction in cancer mortality was observed after a median cumulative follow-up of 22.3 years (1817 vs. 1943 deaths; hazard ratio [HR], 0.93 [95% CI, 0.87 to 0.99]), along with a 6% increase in CVD mortality (2621 vs. 2420 deaths; HR, 1.06 [CI, 1.01 to 1.12]). There was no overall effect on other measures, including all-cause mortality (7834 vs. 7748 deaths; HR, 1.00 [CI, 0.97 to 1.03]).
    Thomson et al., Annals of Internal Medicine, 2024 · checked 2026-09-16 · independently re-checked
28. ca-h03 · Meta-analysis or systematic review · meta-analysis of randomised trials
    Calcium supplements significantly increased the risk of CVD (RR 1.15, 95% CI 1.06-1.25], I2 = 0.0%, n = 14) and CHD (RR 1.16, 95% CI 1.05-1.28], I2 = 0.0%, n = 9) in double-blind, placebo-controlled RCTs, specifically in healthy postmenopausal women.
    Myung et al., Nutrients, 2021 · checked 2026-09-16 · independently re-checked
29. ca-h04 · Meta-analysis or systematic review · systematic review and meta-analysis
    Calcium supplementation was not associated with myocardial infarction, total stroke, heart failure admission, and cardiovascular/all-cause mortality. Further studies are required to examine and understand these associations.
    Yang et al., Heart, Lung and Circulation, 2023 · checked 2026-09-16 · independently re-checked
30. ca-h05 · Observational data · meta-analysis of prospective cohort studies
    Dietary calcium intake was associated with a lower risk of all-cause mortality (Pooled ES for highest v lowest category: 0.95; 95% CI: 0.92-0.99, I2=62.1%, P < 0.001). Supplemental calcium intake was not significantly associated with risk of all-cause, CVD and cancer mortality.
    Asemi et al., Critical Reviews in Food Science and Nutrition, 2022 · checked 2026-09-16 · independently re-checked
31. ca-t1 · Meta-analysis or systematic review · systematic review and meta-analysis of randomised trials
    For the primary outcome of any fracture, little to no effect was found from use of calcium supplements (11 trials, 9067 participants; risk ratio 0.91, 95% confidence interval 0.81 to 1.01; moderate certainty), vitamin D supplements (36 trials, 92 045 participants; 1.00, 0.95 to 1.06; high certainty), or combined supplementation (15 trials, 51 126 participants; 0.91, 0.84 to 0.99; high certainty).
    Bolland et al., BMJ, 2026 · checked 2026-09-17 · independently re-checked
32. ca-t2 · Meta-analysis or systematic review · systematic review and meta-analysis of randomised trials
    Participants in most of the trials were community dwelling (87%) and not at high risk of fractures or falls (73%)...Evidence for high risk patients or those requiring residential care was limited for many outcomes for calcium monotherapy and for combined supplementation.
    Bolland et al., BMJ, 2026 · checked 2026-09-17 · independently re-checked
33. ca-t3 · Meta-analysis or systematic review · systematic review and meta-analysis of randomised trials
    There was no significant association of calcium or vitamin D with risk of hip fracture compared with placebo or no treatment (calcium: RR, 1.53 [95% CI, 0.97 to 2.42]; ARD, 0.01 [95% CI, 0.00 to 0.01]; vitamin D: RR, 1.21 [95% CI, 0.99 to 1.47]; ARD, 0.00 [95% CI, -0.00 to 0.01]. There was no significant association of combined calcium and vitamin D with hip fracture compared with placebo or no treatment (RR, 1.09 [95% CI, 0.85 to 1.39]; ARD, 0.00 [95% CI, -0.00 to 0.00]).
    Zhao et al., JAMA, 2017 · checked 2026-09-17 · independently re-checked
34. ca-t4 · Meta-analysis or systematic review · meta-analysis of randomised trials
    Meta-analysis of all studies showed that calcium plus vitamin D supplementation produced a statistically significant 15 % reduced risk of total fractures (SRRE, 0.85; 95 % confidence interval [CI], 0.73-0.98) and a 30 % reduced risk of hip fractures (SRRE, 0.70; 95 % CI, 0.56-0.87).
    Weaver et al., Osteoporosis International, 2016 · checked 2026-09-17 · independently re-checked
35. ca-t5 · Meta-analysis or systematic review · systematic review and meta-analysis of randomised trials
    Combined supplementation modestly improved BMD at the pelvis (SMD = 0.20, 95% CI: 0.05–0.35, p = 0.01) without significant changes in BMD at the lumbar spine, femoral neck, or total hip. The overall fracture risk was not significantly reduced (RR = 0.98, 95% CI: 0.89–1.07, p = 0.68).
    BMC Musculoskeletal Disorders, 2025 · checked 2026-09-17 · independently re-checked
36. ca-r3-01 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis
    Calcium may result in little to no difference in pre-eclampsia (risk ratio (RR) 0.83, 95% confidence interval (CI) 0.67 to 1.04; 6 RCTs, 15,364 women; risk difference (RD) 9/1000 fewer, 95% CI 17 fewer to 2 more; low-certainty evidence). Sensitivity analysis excluding small studies (fewer than 500 participants) indicates little to no difference in pre-eclampsia (RR 0.92, 95% CI 0.79 to 1.05; 4 RCTs, 14,730 women; high-certainty evidence).
    Cochrane Database of Systematic Reviews, 2025 · checked 2026-09-17 · independently re-checked
37. ca-r3-02 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis
    We included 10 RCTs with 37,504 participants. All trials provided standard care. Eight compared calcium supplementation to placebo, and two compared low- to high-dose calcium supplementation. We excluded 20 previously included trials; 11 because eligibility criteria changed and nine because they are awaiting classification due to trustworthiness issues.
    Cochrane Database of Systematic Reviews, 2025 · checked 2026-09-17 · independently re-checked
38. ca-r3-03 · Meta-analysis or systematic review · Cochrane systematic review of randomised trials
    Compared to placebo, calcium may result in little to no difference in pre-eclampsia or pregnancy loss at any gestational age (risk ratio (RR) 0.85, 95% confidence interval (CI) 0.67 to 1.07; 1 RCT, 1355 women; risk difference (RD) 28/1000 fewer, 95% CI 61 fewer to 13 more; low-certainty evidence)...Compared to placebo, calcium may result in little to no difference in pre-eclampsia (RR 0.84, 95% CI 0.62 to 1.14; 1 RCT, 1355 women; RD 19/1000 fewer, 95% CI 46 fewer to 17 more; low-certainty evidence).
    Cochrane Database of Systematic Reviews, 2025 · checked 2026-09-17 · independently re-checked
39. ca-r3-04 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis
    The effect on systolic and diastolic blood pressure was: mean difference (MD) -1.37 mmHg, 95% confidence interval (CI) -2.08, -0.66; 3140 participants; 18 studies; I2 = 0%, high-certainty evidence; and MD -1.45, 95% CI -2.23, -0.67; 3039 participants; 17 studies; I2 = 45%, high-certainty evidence, respectively.
    Cochrane Database of Systematic Reviews, 2022 · checked 2026-09-17 · independently re-checked
40. ca-c1-11 · Meta-analysis or systematic review · meta-analysis of randomised balance studies
    In conclusion, this meta-analysis does not support the concept that the calciuria associated with higher NAE reflects a net loss of whole body calcium. There is no evidence from superior quality balance studies that increasing the diet acid load promotes skeletal bone mineral loss or osteoporosis.
    Fenton et al., Journal of Bone and Mineral Research, 2009 · checked 2026-09-18 · independently re-checked
41. ca-c1-12 · Meta-analysis or systematic review · meta-analysis of randomised balance studies
    Changes of urine calcium do not accurately represent calcium balance. Promotion of the "alkaline diet" to prevent calcium loss is not justified.
    Fenton et al., Journal of Bone and Mineral Research, 2009 · checked 2026-09-18 · independently re-checked
42. ca-c1-13 · Observational data · prospective cohort studies
    For every glass of milk in women no reduction was observed in fracture risk with higher milk consumption for any fracture (1.02, 1.00 to 1.04) or for hip fracture (1.09, 1.05 to 1.13).
    Michaëlsson et al., BMJ, 2014 · checked 2026-09-18 · independently re-checked
43. ca-c1-14 · Observational data · prospective cohort studies
    Instructions were given that one serving of milk corresponded to one glass of 200 mL.
    Michaëlsson et al., BMJ, 2014 · checked 2026-09-18 · independently re-checked
44. ca-c1-15 · Observational data · stated evidence gap in a prospective cohort study
    The fact that no randomised trial has examined the effect of milk intake on incidence of mortality and fractures, long term experimental evidence is needed to confirm a causal association between higher milk intake and higher mortality.
    Michaëlsson et al., BMJ, 2014 · checked 2026-09-18 · independently re-checked
45. ca-c1-16 · Observational data · systematic review and meta-analysis of composition studies
    Moreover, the statistical heterogeneity was high for all three nutrients (I2 of 100% and significant τ2).
    Dror & Allen, International Breastfeeding Journal, 2023 · checked 2026-09-18 · independently re-checked
46. ca-10 · Observational data · observational evidence cited by expert body
    The ULs for calcium...are based on observational evidence from the WHI showing a link between higher intakes of supplemental calcium (1,000 mg/day for 7 years) and a greater risk of kidney stones.
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Calcium · checked 2026-09-15 · extracted
47. ca-c1-08 · Position of an expert body · national dietary survey
    The average intake of calcium from multi- or single ingredient supplements was 521 mg (3).
    FSRG Dietary Data Briefs, USDA Agricultural Research Service, WWEIA/NHANES 2009-2010 · checked 2026-09-18 · independently re-checked
48. ca-11 · Position of an expert body · expert body statement
    Calcium carbonate supplements can interfere with the absorption of levothyroxine...The FDA-approved label for this medication instructs patients who are taking calcium carbonate supplements to avoid taking levothyroxine within 4 hours of taking the supplement.
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Calcium · checked 2026-09-15 · extracted
49. ca-14 · Position of an expert body · expert body statement
    Simultaneous use of calcium supplements and quinolone antibiotics—such as ciprofloxacin (Cipro), gemifloxacin (Factive), and moxifloxacin (Avelox)—can reduce the absorption of quinolones.
    NIH Office of Dietary Supplements, Calcium - Health Professional Fact Sheet · checked 2026-09-16 · independently re-checked