Calcium citrate, potassium citrate and bone markers in young women
What it found
Potassium citrate lowered a marker of bone breakdown and helped the body hold onto calcium in 12 young women over 24 hours.
Both calcium supplements were absorbed well and lowered a bone-related hormone.
What they found
Studies in people
Bone breakdown marker
Potassium citrate lowered a urine marker that shows bone is breaking down. Calcium carbonate also lowered this marker compared to taking nothing. Calcium citrate did not clearly change it.
Calcium kept in body
Women lost less calcium in their urine after taking potassium citrate compared to the control day. Both calcium supplements led to more calcium leaving in the urine than the control day.
Parathyroid hormone levels
Both calcium supplements lowered parathyroid hormone in the blood, a signal linked to bone loss. Potassium citrate did not change this hormone level.
Bone building marker
None of the three supplements changed a blood marker that tracks new bone being built over the 24-hour period.
Absorption of calcium forms
Blood tests showed both calcium citrate and calcium carbonate were taken up by the body equally well when eaten with a meal. They worked just as well at lowering the bone-related hormone.
What the authors conclude
- They say potassium citrate may reduce bone breakdown and help the body keep calcium even when dietary calcium is low and the diet is not highly acidic.
- They conclude that calcium citrate and calcium carbonate are absorbed equally well and work just as effectively in healthy young women when taken with food.
- The authors note these short-term results need to be confirmed in longer studies.
How it was done
Western diets often lack enough calcium and potassium while providing too much protein, which can create acid in the body and harm bones. The authors wanted to see how different mineral supplements affect short-term bone and calcium markers.
Twelve healthy women aged 20 to 30 years each completed four separate 24-hour sessions spaced a week apart. In each session they took one supplement with breakfast: either 1000 mg of calcium from calcium carbonate, 1000 mg of calcium from calcium citrate, 2250 mg of potassium from potassium citrate, or a dummy pill. Everyone ate the same meals during every session, and researchers measured blood and urine throughout the day.
What it can’t tell you
- This trial lasted only 24 hours per session, so it cannot show what happens to bones over months or years.
- Only 12 young women took part, so the results might not apply to men, older adults or people with health conditions.
Who paid
- Authors work at
- University of Helsinki, Finland
The paper
- Title
- Acute effects of calcium carbonate, calcium citrate and potassium citrate on markers of calcium and bone metabolism in young women
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Karp HJ, Ketola ME, Lamberg-Allardt CJ (2009). Acute effects of calcium carbonate, calcium citrate and potassium citrate on markers of calcium and bone metabolism in young women. The British journal of nutrition. doi:10.1017/S0007114509990195Free full textPubMed 19538811DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error