Calcium ascorbate and immune markers in healthy adults
What it found
In a small trial in healthy adults, a single 500 mg dose of calcium ascorbate changed some vitamin C and immune markers more than the same dose of ascorbic acid.
At 250 mg, the two forms made no difference.
What they found
Studies in people
250 mg dose
At 250 mg, there were no differences between calcium ascorbate and ascorbic acid in plasma or lymphocyte vitamin C, pharmacokinetics, or neutrophil function.
500 mg plasma vitamin C
At 500 mg, calcium ascorbate led to higher DHA in plasma and higher DHA area under the curve compared to ascorbic acid. Ascorbic acid led to higher ASC.
500 mg lymphocyte vitamin C
At 500 mg, calcium ascorbate led to lower ASC and total vitamin C in lymphocytes at 24 and 32 hours compared to ascorbic acid. DHA was lower with calcium ascorbate at 24 hours.
Neutrophil function
At 500 mg, the percentage of neutrophils that had taken in bacteria increased from baseline at 24 hours with calcium ascorbate, but not with ascorbic acid. At 250 mg, no difference was seen between the two forms.
Natural killer cells
In a subset of 33 people from the 500 mg study, natural killer cells increased significantly at 24 hours after calcium ascorbate.
Side effects
No side effects were reported by any participants at any time during the study.
What the authors conclude
“These findings indicate that 500 mg of CA may promote some immune benefits compared to 500 mg of AA ingestion.”
Also in their conclusions
- They conclude that 500 mg of calcium ascorbate may promote some immune benefits compared to 500 mg of ascorbic acid.
- They say that individuals may not need to ingest 1000 mg of vitamin C to observe some benefits on immune markers.
- They recommend further research with an immune challenge, such as intense exercise, to see if the effects are larger.
How it was done
Companies claim some vitamin C forms are better absorbed and retained than plain ascorbic acid. The authors wanted to compare calcium ascorbate with ascorbic acid at lower doses, which have been studied less.
Ninety-three healthy adults took a single 250 mg or 500 mg dose of calcium ascorbate or ascorbic acid, then switched to the other form after a break. Blood was collected over 32 hours to measure vitamin C levels and immune cells.
What it can’t tell you
- The study did not include a true placebo group, so it cannot show what would have happened without any vitamin C.
- The participants were healthy and rested, with no immune challenge, so the results may not apply to people who are sick or under immune stress.
- The study was short, with a single dose, so it cannot show the effects of taking calcium ascorbate over a longer period.
Who paid
- Funding
- Funded by The Bountiful Co. (Ronkonkoma, NY, USA) (from the PubMed record).
- Conflicts
- R.B.K. has conducted grant and contract-funded research on nutritional supplements awarded to the universities with which he has been affiliated, received an honorarium for making scientific presentations, and served as a paid scientific expert. He has no financial conflict of interest with the study sponsor or product evaluated in this study. The remaining coauthors report no financial conflicts of interest.
- Authors work at
- Texas A&M University, USA
The paper
- Title
- Comparative Effectiveness of Ascorbic Acid vs. Calcium Ascorbate Ingestion on Pharmacokinetic Profiles and Immune Biomarkers in Healthy Adults: A Preliminary Study
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Dickerson B, Gonzalez DE, Sowinski R, et al (2024). Comparative Effectiveness of Ascorbic Acid vs. Calcium Ascorbate Ingestion on Pharmacokinetic Profiles and Immune Biomarkers in Healthy Adults: A Preliminary Study. Nutrients. doi:10.3390/nu16193358Free full textPubMed 39408325DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error