Calcium
Research reviewed: Up until 03/2026
Calcium is a dietary supplement with 3 published peer-reviewed studies involving 1,556 participants, researched for Bone Health, Blood Pressure.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Bone Health
StrongBlood Pressure
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Bone Health
To assess the effects of calcium carbonate supplementation over 5 years on bone structure and clinical fracture incidence in elderly women
Study Type
Double-blind, placebo-controlled, randomised trial
Purpose
To assess the effects of calcium carbonate supplementation over 5 years on bone structure and clinical fracture incidence in elderly women
Dose
1,200 mg/day elemental calcium (as calcium carbonate) or placebo
Participants
1,460 elderly women aged β₯ 70 years
Duration
5 years
Results
Researchers observed that calcium supplementation significantly reduced the risk of all clinical fractures by 13% . Bone mineral density (an indicator of bone strength) at the hip was also significantly higher after 5 years in women taking calcium, with a difference of about 1β2%). In addition, cortical bone width at the tibia (the main lower leg bone; thicker bone means stronger structure) was significantly greater, suggesting calcium helped maintain bone strength and structure, reducing fracture risk over time.
To determine whether oral calcium supplementation produces a sustained reduction in bone loss in healthy postmenopausal women with relatively low dietary calcium intake
Study Type
Randomised, double-blind, placebo-controlled trial β extension of a 2-year RCT to 4 years
Purpose
To determine whether oral calcium supplementation produces a sustained reduction in bone loss in healthy postmenopausal women with relatively low dietary calcium intake
Dose
1 g elemental calcium per day (oral tablets) or placebo, with no change in usual diet
Participants
78 women who had completed an earlier 2-year double-blind trial; aged at least 3 years postmenopause at enrolment
Duration
4 years total (2-year extension of the original 2-year trial), with bone density measured every 6 months
Results
Researchers observed that total body bone mineral density (a measure of bone strength) showed a significant slowing of bone loss in the calcium group over the full 4-year period. Specifically, during years 2β4, bone loss was significantly reduced by 0.25% per year. However, there was no significant effect at specific sites like the lumbar spine (lower back bones) or proximal femur (upper thigh/hip area) in years 3β4, suggesting the benefit may vary depending on the part of the body.
Blood Pressure
To determine whether oral calcium supplementation reduces blood pressure in patients with established essential hypertension
Study Type
Randomised, double-blind, placebo-controlled crossover trial
Purpose
To determine whether oral calcium supplementation reduces blood pressure in patients with established essential hypertension
Dose
1 g/day elemental calcium (oral supplement) or placebo
Participants
18 patients with uncomplicated essential hypertension (mild-to-moderate); no antihypertensive medication during the trial
Duration
15 weeks per treatment period
Results
Researchers observed that standing systolic blood pressure (SBPβthe top number in a blood pressure reading, showing pressure when the heart pumps; high levels increase risk of heart disease) was significantly reduced by β8.6 mmHg with calcium supplementation compared to placebo. The effect was stronger in people who had higher urinary calcium excretion (a measure of how much calcium is lost in urine, reflecting how the body handles calcium), with a strong inverse relationship, meaning those losing more calcium in urine had the biggest blood pressure improvements. This suggests calcium may be especially helpful for a specific group of people with this underlying calcium imbalance.
Frequently Asked Questions
Common questions about Calcium research
There are currently 3 peer-reviewed studies on Calcium (Calcium), involving 1,556 total participants. Research covers Bone Health, Blood Pressure. The overall evidence strength is rated as Strong.
The evidence is currently rated as "Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (3 human studies), and reported outcomes.
Calcium has been researched for: Bone Health, Blood Pressure. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 3 out of 3 studies are human trials. Human trials carry more weight in our evidence scoring system.
Similar Supplements
Other supplements researched for similar health goals
