Randomised controlled trialindependent cross-checkabstract checked★ key study I-SOD-124 in-depth review

Phosphoric acid in cola did not increase calcium loss

Carbonated beverages and urinary calcium excretion.

Overview

Heaney RP, Rafferty K. Am J Clin Nutr 2001 · PMID 11522558 · DOI 10.1093/ajcn/74.3.343

In a controlled test, cola-type acid did not increase calcium in the urine; only caffeine did, and only slightly.

Does the study support the specific claim? No · Methodological quality: moderate

Study explained simply

What did the researchers want to find out?: Test whether soft-drink ingredients make the body lose calcium.
How was the study done?: Randomised crossover test of different drinks.
How many people, animals or samples were studied?: Young women who drink soft drinks daily.
What was actually found?: Phosphoric acid had no effect; caffeine a small one.
How large was the observed effect?: About 0.25 mmol extra calcium with caffeine.
What do the results mean in everyday life?: Cola acid does not 'drain' calcium; drinking cola instead of milk may matter more.
What are the study's limitations?: Short-term test.
What does it say about Elawady's specific claim?: Contradicts the mechanism of the claim.
Do the results apply to Germany and Europe?: Applicable.
What can explicitly not be concluded from this study?: Cannot exclude long-term effects.

Do constituents of carbonated beverages (phosphoric vs citric acid, caffeine) increase urinary calcium?

Study design: Randomised controlled trial – Randomised incomplete-block crossover trial of acute beverage effects
Population: Women aged 20-40 who habitually drank >=680 mL carbonated beverages daily
Country: USA
Period: 2001
Sample size: Not stated in abstract
Inclusion and exclusion criteria: Habitual carbonated beverage consumers

Exposure / intervention: Four carbonated beverages (with/without caffeine; phosphoric or citric acid), 567 mL
Comparator: Water (neutral); milk (positive control)
Endpoints: Urinary calcium, pH, acidity, sodium, creatinine over 5 h
Statistical methods: Comparisons with water

Results: Relative to water, urinary calcium rose significantly only with the milks and the two caffeine-containing beverages; excess calciuria about 0.25 mmol, similar to caffeine alone. Phosphoric acid without caffeine produced no excess calciuria and did not augment the caffeine effect.
Absolute risks: not applicable
Authors' conclusion: Net effect of carbonated beverage constituents on calcium economy is negligible; skeletal effects are likely due to milk displacement.

0.25 mmol (about 10 mg) calcium excess is small (stats/C-SOD-08_bone.py).

Directly contradicts the mechanism in C-SOD-08: phosphoric acid did not increase calcium loss.

Long-term studies of phosphoric acid and bone are lacking.

Applicable.

Best direct test of the phosphoric-acid hypothesis; negative.

Multidimensional assessment
Multidimensional assessment
Authenticity of the source	verified
Methodological quality	moderate
Risk of bias	some concerns
Precision of results	low
Directness	direct
Reproducibility	partly replicated
Consistency with the overall evidence	consistent
Regional transferability	high
Adequacy of the interpretation (by the archive)	not applicable

Chronic exposure.