Calcium citrate vs calcium carbonate absorption after weight loss surgery
What it found
In people who had weight loss surgery, calcium citrate led to slightly higher calcium absorption and lower parathyroid hormone levels than calcium carbonate.
The differences were small.
What they found
Studies in people
Calcium absorption
Calcium citrate led to slightly higher calcium levels in the blood over 8 hours compared to calcium carbonate. The difference was small.
Parathyroid hormone
Calcium citrate lowered parathyroid hormone levels more than calcium carbonate, especially from 3 to 6 hours after taking the supplement.
Urinary calcium
People excreted more calcium in their urine after taking calcium citrate than after calcium carbonate, which suggests better absorption.
Surgery type
People who had sleeve gastrectomy absorbed more calcium than those who had gastric bypass or one-anastomosis gastric bypass. There was no difference between the two bypass types.
What the authors conclude
“The study demonstrates that Ca citrate was significantly better than carbonate in reducing PTH levels, enhancing relative Ca bioavailability, and increasing urinary Ca excretion.”
Also in their conclusions
- They conclude that calcium citrate was significantly better than carbonate in reducing parathyroid hormone levels, enhancing relative calcium bioavailability, and increasing urinary calcium excretion.
- They note that despite the statistical significance, the differences were marginal.
- They advise that further studies are necessary to assess the clinical relevance of these findings.
How it was done
After weight loss surgery, the body may absorb less calcium, which can lead to bone loss. The authors wanted to see which calcium supplement, citrate or carbonate, is absorbed better after three common types of weight loss surgery.
They studied 150 adults who had weight loss surgery (Roux-en-Y gastric bypass, sleeve gastrectomy, or one-anastomosis gastric bypass) at least 6 months earlier. Each person took both calcium citrate and calcium carbonate, one week apart, and researchers measured calcium and parathyroid hormone levels in blood and urine over 8 hours.
What it can’t tell you
- This study lasted only 8 hours per supplement, so it cannot show the long-term effects on bone health.
- Most participants were female, so the results may not apply equally to men.
- The study did not measure bone density or other long-term outcomes.
Who paid
- Authors work at
- Alexandria University, Egypt; Bariatric Surgery at Madina Women's Hospital, Egypt; Vrije Universiteit Brussel, Belgium
The paper
- Title
- Comparison of calcium citrate and calcium carbonate absorption in patients with a Roux-en-Y gastric bypass, sleeve gastrectomy, and one-anastomosis gastric bypass: a double-blind, randomized cross-over trial
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Hany M, Wuyts S, Abouelnasr AA, et al (2025). Comparison of calcium citrate and calcium carbonate absorption in patients with a Roux-en-Y gastric bypass, sleeve gastrectomy, and one-anastomosis gastric bypass: a double-blind, randomized cross-over trial. Surgery for obesity and related diseases. doi:10.1016/j.soard.2024.10.034Free full textPubMed 39603923DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error