Calcium citrate and other calcium sources: short-term blood calcium effects
What it found
In ten older women, a single 500 mg dose of calcium citrate raised blood calcium over 6 hours.
The size of the rise depended on whether it was taken alone, with a meal, in fortified juice or as a dairy meal.
What they found
Studies in people
Blood calcium rise
Ionised and total calcium in the blood rose significantly from the starting level over 6 hours after all four calcium sources.
Fortified juice
Using calcium citrate taken while fasting as the comparison, the rises in ionised and total calcium were similar after fortified juice.
Citrate with a meal
The rises in ionised and total calcium were delayed after calcium citrate taken with a meal.
Dairy product meal
The rises in ionised and total calcium were smaller after a dairy product meal.
Phosphate changes
Blood phosphate and the calcium-phosphate product rose from the starting level after calcium citrate with a meal and after a dairy product meal. They fell after calcium citrate taken while fasting and after fortified juice.
Compared with 1000 mg
The rises in blood calcium seen here were only slightly different from those seen after 1000 mg of calcium in an earlier study.
What the authors conclude
“These data indicate that different sources of Ca have different acute effects on serum Ca and support recommendations that dietary Ca might be safer than supplements.”
Also in their conclusions
- They say these data indicate that different sources of calcium have different acute effects on serum calcium.
- They say the findings support recommendations that dietary calcium might be safer than supplements.
- They say whether these differences contribute to differences in cardiovascular risk requires further study.
How it was done
Calcium supplements, but not calcium from food, have been linked to higher cardiovascular risk. The authors wanted to see if different calcium sources have different short-term effects on blood calcium.
Ten women with a mean age of 69 years took part in a randomised cross-over trial. Each received a single 500 mg dose of calcium as citrate, citrate with a meal, fortified juice or a dairy product meal, with at least 6 days between each. Blood was sampled before and 1, 2, 4 and 6 hours after each dose.
What it can’t tell you
- We summarised it from the abstract only.
- This was a small trial of ten women, so the results may not apply to other people.
- It only measured blood calcium and phosphate over 6 hours, so it cannot show whether these short-term changes affect heart health over time.
Who paid
- Authors work at
- University of Auckland, New Zealand
The paper
- Title
- Acute effects of calcium citrate with or without a meal, calcium-fortified juice and a dairy product meal on serum calcium and phosphate: a randomised cross-over trial
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Abstract only
- Cite
- Bristow SM, Gamble GD, Stewart A, Kalluru R, Horne AM, Reid IR (2015). Acute effects of calcium citrate with or without a meal, calcium-fortified juice and a dairy product meal on serum calcium and phosphate: a randomised cross-over trial. The British journal of nutrition. doi:10.1017/S000711451500080XPubMed 25851635DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error