Calcium magnesium oxide

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Study period:

no data available

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Well-documented publication which is considered as supplementary data on the bioavailability of calcium from milk and various commercially available Ca supplements and on the effects of Ca on the utilization of other essential elements. Under physiological conditions, the hydroxyl-ions released from lime following oral adminstration have been neutralised in the GI tract and are therefore not relevant for consideration of toxicokinetics. Therefore for assessment of the metabolic fate of the systemically relevant species of lime following administration via the oral route, the calcium ion Ca2+ is the chemical species of interest. In the current study, calcium was administered in the form of various calcium salts (carbonate, lactate, hydrogenorthophsphate). None of these counter-ions is considered toxicologically relevant: Carbonate is released as CO2 following reaction with gastric juice, lactate is an integral element of mammalian energy metabolism, and phosphate is omnipresent in the body, being part of energy metabolsim or a component of DNA. The objective of the study was the evaluation of any effects of calcium, including its retention and fate in the human body. In view of the the limited relevance of the anionic counter-ions discussed here, calcium released both from lime and calcium carbonate, lactate, or hydrogenorthophsphate, can be considered as structurally equivalent (analogue), and the results of the study can be used by read-across.

Data source

Reference

Reference Type:

publication

Title:

Mineral utilization by rats fed various commercially available calcium supplements or milk

Author:

Greger, J.L.; et al.

Year:

1986

Bibliographic source:

J. Nutr. 117, 717-724

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The bioavailability of calcium from milk and various commercially available Ca supplements and the effects of Ca on the utilization of other essential elements was investigated in two experimental series.

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Calcium carbonate

EC Number:

207-439-9

EC Name:

Calcium carbonate

Cas Number:

471-34-1

Molecular formula:

CH2O3.Ca

IUPAC Name:

calcium carbonate

Constituent 2

Reference substance name:

Calcium lactate

EC Number:

227-266-2

EC Name:

Calcium lactate

Cas Number:

5743-48-6

IUPAC Name:

calcium bis(2-hydroxypropanoate)

Constituent 3

Reference substance name:

Calcium hydrogenorthophosphate

EC Number:

231-826-1

EC Name:

Calcium hydrogenorthophosphate

Cas Number:

7757-93-9

IUPAC Name:

calcium hydrogenorthophosphate

Details on test material:

- Name of test material (as cited in study report): Calcium carbonate
- Name of test material (as cited in study report): Calcium lactate
- Name of test material (as cited in study report): Calcium phosphate dibasic
- Name of test material (as cited in study report): vegetarian amino acid chelated calcium
No further details are given.

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Sprague-Dawley, Indianapolis, IN
- Age at study initiation: weanling rats
- Housing: Rats were housed individually in stainless steel, wire-bottom cages
- Diet: ad libitum
- Water: ad libitum; deionised water

No further details are given.

Administration / exposure

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

DIET PREPARATION
- Nine commercially available calcium supplements and non-fat dry milk were incorporated into diets fed to rats in two studies:
- In study 1, rats were fed diets that contained 1) non-fat dry milk (diet 1MILK), 2) calcium phosphate dibasic (diet 1P), 3) oyster shell calcium (diet 10S), 4) calcium carbonate (diet 1C), 5) calcium lactate (diet 1L), or 6) vegetarian amino acid chelated calcium (diet 1Ch). The non-fat dry milk diet provided 6.45 mg Ca/g diet. The other diets in study 1 were formulated to contain similar levels of calcium.
- In study 2, rats were fed diets that contained 1) non-fat dry milk (diet 2MILK), 2) calcium phosphate dibasic (diet 2P), 3) dolomite (diet 2D), 4) oyster shell calcium with magnesium (diet 2OSMg), 5) chelated calcium and magnesium from yeast (diet 2ChMg), and 6) calcium carbonate with supplemental iron and vitamins (diet 2CFe). All diets were formulated to contain ≈ 5.0 mg Ca/g diet (the level recommended in AIN-76 diet).
- The diets in both studies were formulated to provide 18% protein from either NFDM or casein. In study 1 NFDM provided all the protein in diet 1MILK.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Mineral supplements and diet samples were analysed for calcium, magnesium, iron, zinc and copper by atomic absorption spectroscopy and for phos
phorus content by a colorimetrie procedure.

Duration of treatment / exposure:

- study 1: 20 days
- study 1: 27 days

Frequency of treatment:

continuously

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
5.09-7.29 mg Ca/g (study 1)
Basis:
other: analysed conc. in diets

Doses / concentrations 2

Remarks:

Doses / Concentrations:
1.7-4.4% Calcium supplements, except in diet milk 1 (Study 1)
Basis:
nominal in diet

Doses / concentrations 3

Remarks:

Doses / Concentrations:
5.08-5.68 mg Ca/g (study 2)
Basis:
other: analysed conc. in diets

Doses / concentrations 4

Remarks:

Doses / Concentrations:
1.7-2.6% Calcium supplements, except in diet milk 2 (Study 2)
Basis:
nominal in diet

No. of animals per sex per dose:

36 rats each

Control animals:

not specified

Details on study design:

no data

Positive control:

No positive control substance was tested.

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: Rats were weighed twice a week.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): yes,
- Food consumption was recorded daily

FOOD EFFICIENCY: No data

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: No data

CLINICAL CHEMISTRY: No data

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: No data

OTHER:
- Faecal samples were collected on days 14-18 in study 1 and on days 19-22 in study 2. They were cleaned of foreign adhering matter, dried to a constant weight and ground to a fine powder.
- Mineral supplements, diets, tissue and faecal samples were analyzed fo Ca, Mg, Fe, Zn and Cu by atomic absorption spectroscopy.
- Phosphorous contents was determined by a colorimetric procedure.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes; Rats were anesthetised and killed by exsanguination after being fasted overnight. Kidneys, livers, tibias and ulnas were excised, cleaned of adhering matter and frozen in acidwashed plastic containers.

HISTOPATHOLOGY: No data

Other examinations:

no data

Statistics:

The effects of dietary treatments were evaluated by analysis of variance.Tests for least significant differences were used to differentiate among means for variables that had been significantly affected by the treatments.

Results and discussion

Results of examinations

Clinical signs:

not specified

Mortality:

not specified

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

not specified

Haematological findings:

not specified

Clinical biochemistry findings:

not specified

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

not specified

Histopathological findings: neoplastic:

not specified

Details on results:

BODY WEIGHT, WEIGHT GAIN AND FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
- In study 1, rats fed diet 1MILK had diarrhoea and tended to eat and weigh less than rats fed the other diets that did not contain lactose.
- The differences were significant between rats fed diet 1MILK and diets 1CCh or 1CC for weight and food intake and between rats fed diets 1MILK and 1OS for weight.
- There were no significant differences in food intakes or body weights of rats in study 2.

GROSS PATHOLOGY
- Rats fed the calcium phosphate dibasic had enlarged kidneys with >20-fold increases in Ca levels.

OTHER FINDINGS
- The non-fat dry milk and the other calcium supplements were the sole sources of calcium in nutritionally adequate diets.
- Rats fed the calcium phosphate dibasic tended to have more Mg, P and Zn in their kidneys than other rats.
- Rats fed the three Mg-fortified supplements had lower apparent absorption of Ca and Fe and less accumulation of Ca in bone than rats fed milk.
- There were few differences in the utilization of Ca by rats fed milk or supplement containing only calcium lactate, chelated calcium, oyster shells and calcium carbonate, but Mg retention in bone was greater among rats fed milk.
- Results on zinc levels suggest that in these studies apparent absorption of zinc and the tibia Zn levels were monitoring different aspects of zinc utilization and retention.
- Generally, effects of the dietary treatments on iron metabolism were more consistent than the effects on zinc metabolism.
- Most of the effects appear to be related to the levels of Fe and Mg in the diets, not to differences in the forms of Ca fed.
- The different dietary treatments had little effect on the copper metabolism of rats.

Effect levels

Dose descriptor:

NOAEL

Basis for effect level:

other: Study design not suitable for identification of NOAEL.

Remarks on result:

not determinable

Remarks:

no NOAEL identified

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The study is not appropriate for derivation of a NOAEL.