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Type of information:
experimental study
Adequacy of study:
supporting study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Information well reported in the study but repoted results of low interest

Data source

Reference Type:
On phosphates and phosphoric acid as dietary factors in the calcium balance of man.
Malm O J
Bibliographic source:
Scand J Clin Lab Invest 5 75-84.
Report date:

Materials and methods

Study type:
biological effect monitoring
Endpoint addressed:
repeated dose toxicity: oral
Principles of method if other than guideline:
The experiments to be presented ate the following.
1. Brief ingestion (one week) of 2.37 g orthophosphoric acid daily (750 g P) in four adult men (28, 29, 32 and 43 years of age)
2. Protracted ingestion (four weeks) of 3.16 g of orthophosphoric acid (1000 mg P) daily in two adult men (40 and 43 years of age).
3.Protracted ingestion (eight weeks) of 0.8 g of orthophosphoric acid (250 mg P) daily in four adult men (20, 28, 46 and 56 years of age)
4. Protracted ingestion (twelve weeks) of a neutral (Na -K) phosphate rnixture (600 mg P) daily in two adult rnen (20 and 43 years of age).
All these experiments were carried out in experimental persons who had been observed with regard to their calcium balance for months and years prior to the experiments with addition of phosphoric acid and phosphate. The experiments were carried out under the most careful control of the dietary intake.
In addition, the effect of a very high meat diet (lean beef ) was also studied in four other adult men who were members of the technical staff (27, 28, 38 and 43 years of age) The daily food intalre was measured roughly, and the variations were somewhat larger than in the phosphorus experiments.
It was calculated that the intake of protein was approximately 70-100 g daily during the control period. The protein intake was raised to 210-230 g daily during the seven days of experirnent. The calculated increase in the acidity of the diet was approximately 1200-1400 ml N/10 acid daily.
GLP compliance:

Test material

Constituent 1
Chemical structure
Reference substance name:
Orthophosphoric acid
EC Number:
EC Name:
Orthophosphoric acid
Cas Number:
Molecular formula:
phosphoric acid
Details on test material:
Described in the study report as orthophosphoric acid (84%)

Results and discussion

No ill effects have been observed during the experiment. The proacted ingestion of the highest dose of phosphoric acid (3.16 g) was felt as a strain.
For the 2.37g dose of phosphoric acid given daily for one week to four men: Phosphoric acid is excreted in the urine with the aid of some reduction of the pH, an increase in the titrable acidity and a slight increase in preformed urinari ammonia. No significant changes in the CO2 combining capacity of the plasma, indicating metabolic acidosis, were found, nor were significant variations observed in the urinary excretion of potassium and total fixed bases.
For the 3.16g dose phosphoric acid given daily for four weeks to 2 men: Phosphoric acid reduce the urinary calcium slightly in the one, somewhat more markedly in the other case. The calcium balance remained unchanged by phosphoric acid administration in both cases.
For the 0.8g dose phosphoric acid given daily for eight week to 4 men: No effect on the calcium balances.

Applicant's summary and conclusion

An increase of P-content of the diet by adding phosphoric acid was followed by a reduction of urinary calcium at all doses and for all persons. The higher the dose is the higher the decrease is. Nevertheless the effects of the 0.8g H3PO4 dose were really moderated.
No ill effects have been observed during the experiment. The proacted ingestion of the highest dose of phosphoric acid (3.16 g) was felt as a strain.