Calcium citrate vs calcium carbonate after gastric bypass
What it found
In 18 people who had gastric bypass, calcium citrate was absorbed better than calcium carbonate.
Blood calcium rose higher and parathyroid hormone dropped more with calcium citrate.
What they found
Studies in people
Blood calcium levels
Calcium citrate led to a higher peak blood calcium and a greater total rise over 6 hours than calcium carbonate. The peak was 9.4 mg/dl with citrate versus 9.2 mg/dl with carbonate.
Parathyroid hormone
Blood parathyroid hormone dropped more with calcium citrate. The lowest level was 24 pg/ml with citrate versus 30 pg/ml with carbonate.
Urinary calcium
Urine calcium rose significantly after calcium citrate but stayed unchanged after calcium carbonate. The difference between the two supplements was statistically significant.
Time to peak
Calcium citrate took longer to reach peak blood levels, about 3.6 hours versus 2.1 hours for calcium carbonate.
What the authors conclude
“Calcium citrate has superior bioavailability than calcium carbonate in RYGB patients.”
Also in their conclusions
- They conclude that calcium citrate has superior bioavailability than calcium carbonate in RYGB patients.
- They suggest that calcium citrate may prove to be superior in the reversal of secondary hyperparathyroidism, a condition which may accompany RYGB procedures.
- They call for long-term longitudinal studies to confirm the superiority of calcium citrate supplementation in patients following RYGB.
How it was done
After gastric bypass, food no longer passes through the duodenum, the main site of calcium absorption, so calcium absorption is significantly impaired. The authors wanted to compare two common calcium supplements in these patients.
Eighteen healthy volunteers who had Roux-en-Y gastric bypass about 1 year earlier took a single 500 mg dose of calcium citrate and, in a separate phase, a single 500 mg dose of calcium carbonate. Blood and urine were collected for 6 hours after each dose to measure calcium and parathyroid hormone levels.
What it can’t tell you
- This was a single-dose study over 6 hours. It cannot show the effects of taking these supplements for weeks, months or years.
- The study did not measure actual bone loss or kidney stones, only blood and urine markers.
- The results apply to people who have had Roux-en-Y gastric bypass, not to the general population.
Who paid
- Funding
- Funded by NCRR NIH HHS (from the PubMed record).
- Authors work at
- Charles and Jane Pak Center for Mineral Metabolism, USA
The paper
- Title
- Comparison of the absorption of calcium carbonate and calcium citrate after Roux-en-Y gastric bypass
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Tondapu P, Provost D, Adams-Huet B, Sims T, Chang C, Sakhaee K (2009). Comparison of the absorption of calcium carbonate and calcium citrate after Roux-en-Y gastric bypass. Obesity surgery. doi:10.1007/s11695-009-9850-6Free full textPubMed 19437082DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error