CALCIUM ASCORBATE
Explanation
Ascorbic acid and potassium and sodium ascorbate were evaluated
for acceptable daily intake by the Joint FAO/WHO Expert Committee on
Food Additives in 1974 (see Annex, Ref. 32). A Toxicological monograph
was issued in 1974 (see Annex, Ref. 33).
Since the previous evaluation, additional data have become
available and are summarized and discussed in the following monograph.
The previously published monograph has been expanded and is reproduced
in its entirety below.
BIOLOGICAL DATA
BIOCHEMICAL ASPECTS
Ascorbic acid is readily absorbed and metabolized. However, after
oral administration of large quantities only small amounts are
excreted in the urine, while there is a steady rise in the level of
ascorbic acid in the plasma. If the oral ingestion is continued for a
sufficient period, the plasma concentration rises to a maximum, after
which a rapid urinary excretion of a large part of the ingested
ascorbic acid occurs (Abt & Farmer, 1938).
Using 14C-labelled ascorbic acid, it was found that in the rat
after intraperitoneal injection of 1.5-5.9 mg approximately 19 to 29%
was converted to CO2 and only 0.4% was excreted as oxalate within 24
hours (Curtin & King, 1955).
A pharmacokinetic study of the oral administration of ascorbic
acid to male volunteers indicated the half life of ascorbic acid was
inversely related to the administered dose and total turnover of
ascorbate. Under steady state conditions, approached the half life 10
days at a total turnover of 70 mg/day (Kalluer et al., 1979).
In a study involving three patients, the biological half life of
ascorbate in man averaged 16 days; the body pool averaged 20 mg/kg bw
and the turnover rate was about 1 mg/kg/day (Hellman & Burns, 1958).
Metabolism of ascorbate to CO2 does not occur to any great
extent in the human (Baker et al., 1962).
In the 10 days following an i.v. dose of 1-14C-L-ascorbate to
human subjects, 42% of the label was found in the urine, 1% in faeces
and none in expired CO2. Oxalate was the major urinary metabolite,
followed by ascorbate itself and then diketo-L-gulonic acid.
A study carried out in a male volunteer administered
4-3H-L-ascorbate showed that the label did not enter the body water
pool but was excreted as ascorbate and other metabolites (Tolbert et
al., 1967).
TOXICOLOGICAL STUDIES
Special studies mutagenicity
Neither ascorbic acid or calcium ascorbate were mutagenic to
Salmonella typhimurium strains TA-98, TA-100, 1535, 1537 or 1538 or
to Saccharoymyces cervisiae strain D4 when tested in plate or
suspension assay systems with or without metabolic activation (Litton
Bionetics, 1975 & 1976).
Special studies on teratogenicity
Groups of 20 to 23 pregnant female CD-1 strain albino mice were
given doses of 5.2-520 mg/kg of ascorbic acid by oral intubation for
10 consecutive days starting on day 6 of pregnancy. Compared to
concurrent controls, there were no adverse effects reported on
maternal or foetal survival nor were there any increases in soft
tissue or skeletal malformations as a result of treatment.
Groups of 20 to 22 pregnant Wistar derived female rats were
administered, by gavage, doses of 5.5-555 mg/kg of ascorbic acid daily
from days 6 through 15 of gestation, compared to sham treated
controls. No treatment related effects were observed with respect to
maternal or foetal survival or soft tissue or skeletal malformations,
although the incidence of incomplete closure of the skull was the
greatest in the high dose foetuses (Food & Drug Research Laboratories,
1974).
Acute toxicity
LD50 Reference
Animal Route (mg/kg bw)
Mouse Oral 5 000 Demole, 1934
i.v. 1 000
Rat Oral 5 000 Demole, 1934
i.v. 1 000
Guinea-pig Oral 5 000 Demole, 1934
i.v. 500
Short-term studies
Mouse
Mice given ascorbic acid orally, subcutaneously and intravenously
in daily doses of 500-1000 mg/kg bw for seven days, showed no
difference in appetite, weight gain and general behaviour from
controls receiving the same amount of the biologically inactive
galacturonic acid. Histological examination of various organs showed
no definite changes (Demole, 1934).
Rat
Groups of six rats were given ascorbate added to the diet at 0,
1, 5 or 10%. There was a dose related effect on weight gain. Two of
six rats in the high dose group died, laxation also occurred at this
level (De Albequerque & Henriques, 1970).
Guinea-pig
Guinea-pigs given ascorbic acid orally, subcutaneously and
intravenously in daily doses of 400-2500 mg/kg bw for six days, showed
no difference in appetite, weight gain and general behaviour from
controls receiving the same amounts of the biologically inactive
galacturonic acid. Histological examination of various organs showed
no definite changes (Demole, 1934).
Long-term studies
Rat
Four groups of 26 male and 26 female rats were given in their
diet for two years daily doses of 0, 1000, 1500 or 2000 mg/kg bw of
L-ascorbic acid. Haematological examinations, urine analysis, blood
enzyme activity, liver and renal function tests yielded results within
the normal range of values observed in the control group.
No macro- or micropathologically detectable toxic organic lesions
were observed which could be attributed to the daily ingestion of
large doses of L-ascorbic acid. Age-dependent degenerative processes
in organs, increasing predisposition of aging animals to intercurrent
diseases and the appearance of spontaneous tumours occurred at the
same rates in control animals as in those treated (Surber & Cerioli,
1971).
OBSERVATIONS IN MAN
One woman and three men were each given 1000 mg of ascorbic acid
a day for three months. The ascorbic acid levels in the serum and in
the white blood cells and the urinary excretion of this acid did not
show any progressive changes. Further, no harmful effects were
observed in these four subjects during the three months (Lowry et al.,
1952).
After a daily dose of 5 mg/kg for three days a significant
increase in urinary volume was observed in 30 children, 10 active
rheumatic, 10 convalescent rheumatic patients and 10 controls (Abbasy,
1937). This diuretic effect was confirmed in another study on nine
patients with heart failure, given 300 mg of ascorbic acid daily
(Evans, 1938).
Doses up to 6000 mg of ascorbic acid were given to 29 infants, 93
children of preschool and school age, and 20 adults for more than 1400
days. With the higher doses, toxic manifestations were observed in
five adults and four infants. The signs and symptoms in adults were
nausea, vomiting, diarrhoea, flushing of the face, headache, fatigue
and disturbed sleep. The main toxic reactions in the infants were skin
rashes (Widenbauer, 1936).
In order to test the efficacy of ascorbic acid therapy against
the common cold there have been a number of human studies in which
persons were given large daily doses of vitamin C. For example,
Anderson et al. (1972) enrolled 1000 volunteers in a double blind
study in which half the subjects took four tablets containing 250 mg
each of ascorbic acid while the other half took four tablets daily of
a placebo. The study lasted three months. Subjects were instructed to
increase their intake to 16 tablets daily for the first three days of
any illness. A total of 28 subjects dropped out of the study because
of suspected side effects, 15 had been taking the vitamin and 13
placebo. Specific complaints such as nausea, cramps, skin rash, etc.
were approximately evenly divided between individuals ingesting
ascorbate and placebo. Of the 818 persons who remained on the study
for three months, 12% of these taking ascorbic and 11% of the placebo
users reported unusual symptoms.
A group of 311 subjects who took part in a double blind study
were divided into four groups and received from 0 to 6 g daily of
ascorbic acid in a series of divided doses. An additional 6 g (or
placebo) were taken daily for five days if the subject was suffering
from a cold. The study was continued for nine months. No side effects
were noted in the placebo or ascorbate group. The report stated that
no ascorbic acid "toxicity" was found in the following laboratory
tests: albumin, globulin, alkaline phosphatase, total bilirubin,
calcium, cholesterol, glucose, lactic acid, LDH, BUN, uric acid and
alanine amino transferase (Lewis et al., 1975).
A study carried out in school-age children utilized 44 pairs of
identical twins. One member of each pair received, depending on body
weight, 500, 750 or 1000 mg of vitamin C daily while the other member
of the pair received a placebo. The study lasted five months. No
significant effects of treatment were noted with respect to blood
pressure, height, weight, tonsil or cervical node size, white or
red cell count, liver function tests, uric acid, cholesterol,
electrolytes, total protein, albumin and tests of mental alertness and
cognitive processing (Miller et al., 1977).
There are conflicting data in the literature regarding the
question of destruction of vitamin B12 in food by large amounts of
ascorbate (Newmark et al., 1976; Herbert & Jacob, 1974). However, one
brief report indicated that vitamin B12 deficiency may occur in 2 or
3% of adults who ingested 500 mg or more of ascorbate daily (Hines,
1975).
Daily administration of ascorbic acid for three to five days to
14 adult volunteers was reported to increase the lytic sensitivity of
the subjects' erythrocytes to hydrogen peroxide (Mengel & Green,
1976).
Five male patients were dosed daily with 200 mg of ascorbic acid
for 15 days then with 2 g for an additional 15 days. Biochemical
studies performed on leucocytes obtained from the subjects indicated
stimulation of hexose monophosphate shunt activity in resting
leucocytes, and significant impairment of bacterial killing by
leucocytes. The effects were reversible (Shilotri & Seetharam, 1977).
Long-term ingestion of very large doses of ascorbate may lead to
a state of dependency upon these larger doses in guinea-pigs and man
(Rhead & Schrauzer, 1971; Sorensen et al., 1974). The subject has
recently been reviewed (SCOGS, 1979).
Self-administration of ascorbate for a cold was reported to
interfere with warfarin therapy in a female patient (Rosenthal, 1971).
It was reported that a healthy young male receiving 4 g daily of
ascorbate as a supplement excreted up to 622 mg daily of oxalate as
compared to a value of 58 mg prior to supplementation. The usual
increase in oxalate output following supplementation with 4 g
ascorbate was reported to be 12 mg (Briggs, 1973).
Comments
Animal studies reveal that ascorbic acid is not toxic after
single or repeated administrations of relatively large doses.
Oxalate is the major urinary metabolite of ascorbic acid.
However, it is unlikely that the use of the Ca salt will increase the
risk of crystalluria and the formation of calcium oxalate stones,
since the intake of calcium from this source would be minor compared
to the total diet intake of calcium.
Some studies in man indicate that ascorbic acid has a diuretic
effect at 5 mg/kg bw in the children and adults and glycosuria was
observed with doses of 30-100 mg/kg. However, these effects were not
noted in other large-scale double blind studies. Daily doses, of the
order of 100 mg/kg or more, have been taken over periods of time for a
therapeutic effect. In general no adverse effects were noted in these
studies. The recommended dietary allowance ranges from 30-75 mg with a
minimum of 5-10 mg per day. It is estimated that the daily intake of
ascorbic acid is between 30-100 mg from natural sources.
The Committee considered that the evaluation of ascorbic acid and
its salts had relevance only with respect to the food-additive use of
these substances, and their use as a vitamin C supplement in the
usually accepted levels of intake for nutritional purposes. Since
oxalate is a major metabolite of ascorbate, the use of the calcium
salt in large amounts might increase the risk of crystalluria and the
formation of calcium oxalate stones. However, the Committee concluded
that in regard to food-additive and nutritional use, the intake of
calcium from ascorbate would represent only a small fraction of the
total dietary intake of calcium. Therefore it was not envisaged that
the use of calcium ascorbate required any special restriction. The
Committee concluded that the ADI for ascorbic acid and its potassium
and sodium salts should be changed from 0-15 mg/kg bw to "not
specified" and that the calcium salt should be included in this
acceptance.
EVALUATION
ADI not specified.*
* The statement "ADI not specified" means that, on the basis of the
available data (toxicological, biochemical, and other), the total
daily intake of the substance, arising from its use or uses at
the levels necessary to achieve the desired effect and from its
acceptable background in food, does not, in the opinion of the
Committee, represent a hazard to health. For this reason, and for
the reasons stated in individual evaluations, the establishment
of an acceptable daily intake (ADI) in mg/kg bw is not deemed
necessary.
REFERENCES
Abbasy, M. A. (1937) The diuretic action of Vitamin C, Biochem. J.,
31, 339-342
Abt, A. F. & Farmer, C. J. (1938) Vitamin C pharmacology and
therapeutics, J. Amer. Med. Ass., 111, 1555-1565
Anderson, T. W., Reid, D. B. & Beaton, G. H. (1972) Vitamin C and the
common cold: a double-blind study, Canadian Medical Assoc. J.,
107, 503-508
Baker, E. M. et al. (1962) Tracer studies of vitamin C utilization in
men: Metabolism of D-glucolronolactone-6-C14, D-glucuronic-6-
C14, and L-ascorbic-1-C14 acid, Proc. Soc. Exp. Med. Biol.,
109, 737-741
Briggs, M. H., Garcia-Webb, P. & Davies, F. (1973) Urinary oxalate and
vitamin C supplements, Lancet, 2, 201
Curtin, C. O. H. & King, C. G. (1955) The metabolism of ascorbic
acid-1-C14 and oxalic acid-C14 in the rat, J. Biol. Chem.,
216, 539-548
Demole, V. (1934) CVII. On the physiological action of ascorbic acid
and some related compounds, Biochem. J., 28, 770-773
De Albuquerque, A. & Henriques, M. A. (1970) Toxicity of ascorbic
acid, Rev. Port. Farm., 20, 41-46
Evans, W. (1938) Vitamin C in heart failure, Lancet, I, 308-309
Food and Drug Research Laboratories, Inc. (1974) Unpublished report.
Teratologic evaluation of FDA 71-65 (ascorbic acid) in mice and
rats. Final report submitted by the U.S. Food and Drug
Administration.
Hellman, L. & Burns, J. J. (1958) Metabolism of L-ascorbic acid-1-C14
in man, J. Biol. Chem., 230, 923-930
Herbert, V. & Jacob, E. (1974) Destruction of vitamin B 12 by ascorbic
acid, J.A.M.A., 230, 241-242
Hines, J. D. (1975) Letter: Ascorbic acid and vitamin B 12 deficiency,
J.A.M.A., 234, 24
Kallner, A., Hartmann, D. & Horbug, D. (1979) Steady-state turnover
and body pool of ascorbic acid in man, Amer. J. Clin. Nut.,
32, 530-539
Lewis, T. L. et al. (1975) A controlled clinical trial of ascorbic
acid for the common cold, Ann. N.Y. Acad. Sci., 258, 505-512
Litton Bionetics, Inc. (1976) Mutagenic evaluation of calcium
ascorbate. Final report submitted by the U.S. Food and Drug
Administration
Litton Bionetics, Inc. (1975) Mutagenic evaluation of ascorbic acid.
Final report submitted by the U.S. Food and Drug Administration
Lowry, O. H., Bessey, O. A. & Burch, H. B. (1952) Effects of prolonged
high dosage with ascorbic acid, Proc. Soc. Exp. Biol., 80,
361-362
Mengel, C. E. & Greene, H. L., jr (1976) Letter: Ascorbic acid effects
on erythrocytes, Ann. Int. Med., 84, 490
Miller, J. Z. et al. (1977) Therapeutic effect of vitamin C. A co-twin
control study, J.A.M.A., 237, 248-251
Newmark, H. L. et al. (1976) Stability of vitamin B 12 in the presence
of ascorbic acid, Amer. J. Clin. Nutr., 29, 645-649
Rhead, W. J. & Schrauzer, G. N. C. (1971) Risks of long-term ascorbic
acid overdosage, Nutr. Rev., 29, 262-263
Rosenthal, G. (1971) Interaction of ascorbic acid and warfarin,
J.A.M.A., 215, 1671
SCOGS (1979) Evaluation of the health aspects of ascorbic acid, sodium
ascorbate, calcium ascorbate, erythorbic acid, sodium
erythorbate, and ascobyl palmilate as food ingestients SCOGS-59).
Report prepared for U.S. Bureau of Foods, Food & Drug
Administration. Contract No. FDA 223-75-2004
Sorensen, D. I., Devine, M. M. & Rivers, J. M. (1974) Catabolism and
tissue levels of ascorbic acid following long-term massive doses
in the guinea pig, J. Nutr., 104, 1041-1048
Surber, W. & Cerioli, A. (1971) A two-year toxicity study with
L-ascorbic acid on the rats. Unpublished report of the Battelle
Laboratories submitted by Hoffman-La Roche AG
Tolbert, B. M. et al. (1967) Metabolism of L-ascorbic-4-3H acid in
man, Amer. J. Clin. Nutr., 20, 250-252
Widenbauer, F. (1936) Toxic secondary effects of ascorbic acid-C
hypervitaminosis, Klin Worchschr., 15, 1158
See Also:
Toxicological Abbreviations
CALCIUM ASCORBATE (JECFA Evaluation)