ALGINIC ACID AND ITS AMMONIUM, CALCIUM, POTASSIUM AND SODIUM SALTS First draft prepared by Dr G.J.A. Speijers and Mrs M.E. van Apeldoorn National Institute of Public Health and Environmental Protection Laboratory for Toxicology Bilthoven, The Netherlands 1. EXPLANATION These substances were evaluated at the seventh and seventeenth meetings of the Committee (Annex 1, references 7 and 32). At the seventeenth meeting, an ADI of 0-50 mg/kg bw was established. Since these evaluations, additional data have become available and were reviewed by the Committee at its present meeting. Alginate solutions of different viscosities are used as texture modifiers in a wide variety of food and industrial applications. 2. BIOLOGICAL DATA 2.1 Biochemical aspects 2.1.1 Absorption, distribution and excretion 14C-Labelled alginates were fed as 10% of the diet to 10-week-old rats that had been starved for 24 h; and the subsequent metabolism over a 17 h period was measured. Eighty-five to ninety-one % of the radioactivity was recovered in the faeces. Recoveries of administered 14C in urine (0.11-0.16%), respiratory CO2 (0.21-0.42%), and plasma (0.002-0.007%), show that alginate absorption under these conditions of feeding is extremely small (Humphreys & Triffitt, 1968). From the clinical experiments reported it appears that alginic acid does not bind sodium in man to any great extent (Feldman et al., 1952; Gill & Duncan, 1952). The absorption of orally administered riboflavin-5'-phosphate by healthy male subjects was increased significantly when the vitamin was administered in 50 ml of 2% alginate solution rather than water alone (Levy & Rao, 1972). 2.2 Toxicological studies 2.2.1 Acute toxicity Table 1. Acute toxicity of alginic acid and its salts Compound Animal Route LD50 References (mg/kg bw) Alginic acid rat i.p. 1600 Thienes et al., 1957 Sodium mouse i.v. less than 200 Solandt, 1941 alginate Sodium mouse i.p. LDLO 500 Arora et al., alginate 1968 Sodium rat oral >5000 Woodward alginate Research Corp. 1972 Sodium rat i.v. 1000 Sokov, 1970 alginate Sodium rabbit i.v. approx. 100 Solandt, 1941 alginate Sodium cat i.p. approx. 250 Chenoweth, 1948 alginate Calcium rat i.v. 64 Sokov, 1970 alginate Calcium rat i.p. 1407 Sokov, 1970 alginate Subcutaneous and intramuscular injections of 0.1 ml of a 1% dispersion of alginic acid were not followed by any injurious reactions in mice or rats (Chenoweth, 1948). 2.2.2 Short-term studies 2.2.2.1 Rats Potassium alginate at a level of 5% in the feed acted as a laxative; calcium alginate 5% was without this effect (Thienes et al., 1957). Groups of 4 male and 4 female Charles river CD rats were fed a control diet or a diet with 10% sodium alginate at the expense of starch for 12 days. Faecal lipids were increased 5 times in the alginate group. Total blood cholesterol was decreased but not significantly. Total faecal sterols were somewhat increased (Mokady, 1973). When male Sprague-Dawley rats (5-7/group) received for 2 or 4 weeks a non-fibre diet in which 5% sucrose was substituted by 5% sodium alginate, pancreatic-bile secretion was elevated. When alginic acid or calcium alginate was fed, no effect on pancreatic and biliary secretion was observed (Ikegami et al., 1989). Groups of ten 21-day old male Wistar rats received a diet with 10% casein or 10% soybean proteins with 0, 0.5, 1, 2 or 3% sodium alginate for 4 weeks. Sodium alginate had no effect on the protein efficiency ratio (Mouecoucou et al., 1990). Groups of 5 rats were fed 5%, 10% or 20% of alginic acid in the diet for two months. Rats on the 20% diet showed a decreased food consumption and weight gain. Those on lower levels were unaffected (Thienes et al., 1957). Groups of 6 rats were fed sodium alginate for 10 weeks at levels of 5%, 10%, 20% and 30% in the diet. The mortality rate was high in the 20% and 30% groups during the first two weeks, apparently due to inanition. Ten per cent or 5% in the diet had no effect on longevity. The weight gain of the 10% group was slightly decreased. Five per cent had no effect on weight gain (Nilson & Wagner, 1951). Groups of 10 male and 10 female Wistar rats (bw 46.0-47.3 g) received for 4 or 13 weeks 0, 0, 5, 15 or 45% low viscosity sodium alginate in their diet. Body weights were recorded weekly. Food consumption was determined at weeks 1-4 and weeks 12-13. During the first week faeces were collected. Appearance of faeces was judged at intervals during 90 days. After 4 weeks one control group and the 5 and 45% groups were discarded. At week 13 haematology (Hb, Ht, Er, Leu, Diff) in all rats was carried out. In week 14 all rats were killed, relative organ weights were determined, macroscopy and microscopy (approximately 25 tissues) in all rats were carried out. In the first weeks rats on 45% sodium alginate showed abnormal hair loss resulting in practically complete baldness. Heavy diarrhoea was seen in the 45% group in the initial phase of the study. In the 15% group only slightly abnormal faeces were produced during the first weeks. In the 45% group considerable growth retardation was observed. At the 15% level growth was normal. In the final 2 weeks of the study the batch of sodium alginate had to be replaced by another sample. The feeding of the new material caused a sharp drop in body weight followed by a recovery which had not yet been completed at the end of week 12. Low food intake in the 15% group in the final week of the study is ascribed to the change of the test batch. The amount of faeces produced per 100 g of food consumed was considerably increased in rats fed sodium alginate. Haematology did not show abormalities. A significantly increased weight of the caecum, both filled and empty, was seen in the 15% sodium alginate group. Macroscopy showed enlarged, distended, heavy caeca. Histopathology revealed thickened urothelium with papillomatous appearance in the urinary bladder of 6/10 male and 3/10 female rats on 15% sodium alginate. Small calcium deposits under the sometimes thickened urothelium of the renal pelvis and/or under the surface of the renal papilla were seen in 6/10 male and 2/10 female rats on 15% sodium alginate. These changes were not seen in the control group (Feron et al., 1967). 2.2.2.2 Guinea-pigs Two groups of five adult male albino guinea-pigs were given 1% sodium alginate in their drinking water for 10 weeks. A further four groups of six animals were used for a seven-month study. No ill effects were observed and no colon ulceration occurred (Watt & Marcus, 1972). 2.2.2.3 Dogs Groups of each six beagle dogs (equally divided by sex), were maintained on diets containing 0, 5 or 15% sodium alginate for one year. Weight gain, behaviour, appearance, periodic blood values, terminal urinalysis, blood urea nitrogen, blood glucose and serum alkaline phosphatase were within normal limits. Gross autopsy and histopathologic examination of tissues revealed no compound-related effects (Woodard Research Corp., 1959). 2.2.3 Long-term/carcinogenicity studies 2.2.3.1 Mice Groups of 75 male and 75 female Swiss mice (age 6 weeks) received for 89 weeks a control diet or a diet containing sodium alginate at a dose level gradually increasing to 25% (week 39). Sodium alginate was incorporated into the control diet at the expense of equal amounts of the precooked control starch. The mice were observed daily for condition, behaviour and the appearance of faeces. Body weights were recorded at weeks 1, 2 and 4 and once every 4 weeks thereafter. Water intake was measured in at least 5 animals/sex/group in week 87. Haematology was performed in 10 animals/sex/group in weeks 40 and 78. Blood glucose and urea-nitrogen levels were determined in 10 animals/sex/group in weeks 78 and 86 after overnight fasting. Urinalysis was conducted in at least 5 males/group and 8 females/group in weeks 82 and 86, respectively. In week 87 half of the surviving male and female animals in the treated group were placed on control diet and 2-5 weeks later urinalysis was performed in 6-8 males. The pH of faeces was measured in 4-5 males/group in weeks 82 and 85. In week 80, 10 animals/sex/group and in weeks 89-92, all surviving animals were killed, organ weights were determined and macroscopy and microscopy were carried out. In the male control group between weeks 39 and 65, and in the male alginate group during the last six months, high mortality occurred due to haemorrhagic myocarditis. This phenomenon is not uncommon in this strain of mouse. Mean body weights in the alginate group were decreased from week 8 onwards in males and from week 20 onwards in females. Alginate was nephrotoxic to mice as shown by extremely high water consumption (5-10 times control value), high urine production, urinary incontinence (8 males and 2 females), high pH and low specific gravity of the urine, increased level of blood urea nitrogen, increased kidney weights, distension of renal calyx and a high incidence of dilated distal tubules. Furthermore caecal and colonic enlargement and urinary changes were seen, but these changes appeared to be reversible and had completely or largely disappeared within 2-5 weeks after cessation of treatment in week 87. The incidence of intratubular calcinosis or of concretions in the pelvic space was not reduced during the recovery period. In mice no renal pelvic calcification accompanied by hyperplasia of the papillary and pelvic epithelium, as seen in rats fed 15% sodium alginate in their diet, was observed. Probably the high water consumption together with the high production of urine with a low specific gravity prevented formation and deposition of calcareous concretions in the pelvic space of the kidneys of the mice on 25% sodium alginate. Furthermore, in mice no hyperplasia of the epithelium of the urinary bladder, as was seen in rats on 15% sodium alginate, was observed. No indication for a carcinogenic activity of sodium alginate in mice was seen (Til et al., 1986). Infant albino mice (ICR/HA strain) were injected subcutaneously in the nape of the neck with suspensions of alginic acid (10 and 100 mg/ml) or solvent alone in volumes of 0.1, 0.1, 0.2, and 0.2 ml on days 1, 7, 14, and 21 respectively after birth (so total dose in the two test groups was 6 and 60 mg alginic acid, respectively), and maintained on normal diets for 49 to 53 weeks. The initial number of mice was 170, 20 and 79, respectively, in the solvent control group, the 6 mg group and the 60 mg group. Tumour frequency fell within control ranges. At 21 days 16 out of 20 mice in the 6 mg group and 16 out of 79 mice in the 60 mg group were alive, whereas in the solvent control group 147 out of 170 animals were alive. At week 49, 10 out of 20 mice in the 6 mg group and only 11 out of 79 mice in the 60 mg group were alive, whereas in the solvent control group 118 out of 170 animals were alive. Due to the limited number of animals in the lowest dosage group, the low number of survivors in the highest dosage group and the short duration of the experiment, the study is considered to be inappropriate for evaluation of a possible carcinogenic effect of alginic acid (Epstein et al., 1970). 2.2.3.2 Rats Two groups of 10 male albino rats were fed two different commercial preparations of sodium alginate at the 5% level over their lifespan (maximum 128 weeks). Data on longevity, maximum weight and food and water consumption indicate no adverse effect. Gross necropsy studies revealed no abnormalities. Histopathological examination was not carried out (Nilson & Wagner, 1951). 2.2.4 Reproduction studies 2.2.4.1 Rats Groups of 40 rats (equally divided by sex) were maintained on diets containing 0 or 5% sodium alginate for a period of two years. During this period approximately half the rats were bred once to produce an F1-generation, which was subsequently bred to produce an F2-generation. There were no significant differences in growth rate of test groups and controls, for either the parent group over the two-year period or the progeny (F1 and F2). Reproductive performance was normal. Haematological values of the parent group, as well as those of the F2 offspring, were normal. Gross and microscopic study of various tissues and organs of the parent groups at two years, and of the F1 and F2 groups at the conclusion of the rapid growth period, were normal (Morgan et al., undated). 2.2.5 Special studies on genotoxicity Table 2. Results of genotoxicity assays on sodium alginate Test system Test object Dose-levels Results References used Ames test Salmonella up to 10 negative1 Isidate et typhimurium mg/plate al., 1984 Chromosomal Chinese hamster up to 10 negative2 Isidate et aberrations lung cells mg/ml al., 1984 (CHL cells) Chromosomal Chinese hamster 1, 50, 100 negative2 Larripa et aberrations ovary cells µg/per ml al., 1987 Dominant ICr/Ha Swiss i.p. 82, negative3 Epstein et lethal assay mice 200, 1000 al., 1972 mg/kg bw 1 Assay with metabolic activation. 2 Assay without metabolic activation. 3 Test compound alginic acid. 2.2.6 Special studies on immunotoxicity 2.2.6.1 Mice Four mice received an injection with 100 µg of sodium alginate (derived from Mycrocystis pyriforma) 4 days before and at the day of inoculation with sheep red blood cells. Mice were bled 7 days after inoculation and serum was assayed for antibodies against sheep red blood cells by haemagglutination. Sodium alginate caused a significant increase in haemagglutination titer. However when the test was repeated the result was negative (Mayer et al., 1987). 2.2.7 Special studies on tumour inhibition 2.2.7.1 Rats Two groups of 10 male Spague-Dawley rats (age 5 weeks) received weekly for 12 weeks a s.c. injection with a solution of dimethylhydrazine (DMH) (dose 20 mg DMH/kg bw adjusted to pH 7 with sodium bicarbonate). One group received a basal diet while the second group received 1.5% sodium alginate (crude) in their diet during the 12 weeks of DMH treatment. The experiment was terminated 8 weeks after the treatment period. Sodium alginate appeared to exert an inhibitory effect on the development of intestinal tumours resulting from DMH (Yamamoto & Maruyama, 1985). 2.2.8 Special investigations on the interference of alginate with minerals Two groups of 12 male weanling Sprague-Dawley rats received a control diet or a diet with 10% Na-alginate, at the expense of corn starch, for 8 days. A marked increase in faecal dry matter was seen in the alginate group. Ca and Zn absorption were not affected by alginate. Absorption of Fe, Cr, and Co were significantly reduced in the alginate group (Harmut-Hoene & Schelenz, 1980). 2.2.8.1 Interference with Cd and Pb In vitro Equilibrium dialysis experiments were carried out in solutions containing varying concentrations of either Cd (as Cd(OH)2) in saline or Pb (as lead acetate) in water with or without the addition of 1 g alginic acid/100 ml. Equilibration lasted for a minimum of 24 h at room temperature. The extent of the binding by alginate increased as metal concentration increased. At concentrations of 10 and 50 µg Pb/L, 0.7 and 5 mg Pb, respectively, was bound per g alginic acid. At concentrations of 0.01, 0.1, 5 and 10 µg Cd/L 0.09, 0.4, 2.1 and 7.5 mg Cd, respectively, were bound to 1 g alginic acid (Rose & Quarterman, 1987). Rats A group of 6 male rats received for 4 weeks a diet supplemented with 200 mg Pb/kg (as lead acetate) together with 5 mg Cd/kg (as cadmium hydroxide). Furthermore, 40 g alginic acid/kg of diet was added. A control group of 10 male rats received the Pb/Cd supplemented diet without the addition of alginic acid. Deposition of Pb and Cd in liver, kidneys and femur was measured. A reduction of growth was seen in the alginic acid group. Alginic acid had no effect upon Cd deposition, but Pb content in femur and kidneys was doubled. Five groups of 6 male rats received 0, 1, 5, 10 or 40 g alginic acid in their diet for 4 days. On the third day all rats received by stomach tube 0.2 ml saline containing 2 µg radioactive Pb. On day 4 the rats were killed and radioactivity in blood, duodenal mucosa, liver, kidney and gut-free carcass was measured. Pb retention was already increased at 1 g alginic acid/kg of diet (Rose & Quarterman, 1987). Humans In a limited trial with 3 human volunteers, the absorption of 203Pb was unchanged by alginate supplement (Harrison et al., 1969). 2.2.8.2 Interference with radium Mice Male mice (C57 Black, age 3 months) given a single i.p. injection with 226RaCl2 and fed from day 3 thereafter with bread containing 10% sodium alginate (intake Na-alginate was 13 g/kg bw) showed a reduction of the 226Ra content in the femur without decalcification. The amount of 226Ra decorporated was independent of the dose of 226Ra injected i.p. 226Ra content of blood was doubled and 226Ra content of faeces showed a 60% increase. Urinary level of 226Ra was not changed significantly (Kestens et al., 1980). Mice (BALB/c, age 3 months), given bread with 6% sodium alginate 2 h before oral administration (by gavage) of 226RaCl2, revealed a more than 100 times reduction of Ra uptake (measured in whole body). In the same experiment 47Ca uptake was only 1.2 times less than in controls (Vanderborght et al., 1971). 2.2.8.3 Interference with strontium Humans and animals Several experiments in humans and animals which demonstrated a reduction of Sr uptake when Sr isotopes were administered very early before or together with alginate, in the majority of the cases via the oral route. In animals reductions of Sr intake of 1.2 to 10-fold were measured. The radioactive Sr isotopes were determined in carcass, skeleton, femur or whole body. In humans reductions in Sr uptake of 1.6 to 24--fold were reported. Radioactive Sr isotopes were measured in whole body or plasma (Vanderborght et al. 1971). Mice Male C57 Black mice (which had been contaminated with 85Sr 3 weeks previously) were fed a dough containing 5% sodium alginate showed an increased 85Sr content of the blood (Vanderborght et al., 1971). It was hypothesized that the increased 85Sr content in blood was due to a shift in Sr-equilibria between intestinal lumen, blood and the skeleton (Van Barneveld et al., 1977). Simultaneous i.p. and oral (via a diet with starch containing dough) treatment of male Black mice with sodium alginate which had been contaminated with 85Sr 9 weeks previously, resulted in a 5-fold increase of the blood content of 85Sr. 85Sr content of liver, kidney and spleen is increased 4-6 times by this combined treatment. Urinary and faecal excretion of 85Sr were increased 1.2 and 1.8 times, respectively. Treatment with dietary alginate only caused a 2.5-fold rise in blood 85Sr content, 1.5-2 times increases of 85Sr contents in liver, spleen and kidney, a 2.1 times rise in faecal excretion of 85Sr and urinary excretion was somewhat lowered. I.p. treatment with alginate only resulted in a 2.3-fold increase in blood 85Sr content, 2.3-3.6-fold increases of 85Sr contents of liver, spleen and kidney and a 1.7-fold increase in urinary 85Sr excretion, while faecal excretion was not changed. The biological half-life of Sr is about halved by the treatment with alginate via the diet together with i.p. alginate injection. Treatment with alginate via the diet only will speed decorporation of Sr from skeleton by about 40% (Vanderborght et al., 1978). 2.2.8.4 Interference with calcium Rats Rats received diets supplemented with calcium and phosphate with and without 10% sodium alginate. No effect on the absorption and skeletal retention of calcium was observed (Slat et al., 1971). Humans Calcium balance experiments on six healthy adults taking 8 g of sodium alginate daily for seven days failed to show any interference with the absorption of calcium from a normal mixed diet (Millis & Reed, 1947). In 14 out of 15 men receiving 1.5 g sodium alginate the gastrointestinal content of strontium was reduced by a factor of two while calcium absorption was hardly affected (Harrison et al., 1966). The absorption and retention of 47Ca and 85Sr was compared for four human volunteers on a normal diet with and without sodium alginate supplement. Fifteen to twenty grams alginate/day was given for seven days. Alginate decreased the retention of 85Sr and 47Ca by about 70 and 7%, respectively. No changes in excretion pattern of Na, K, Mg or P were observed (Carr et al., 1968). 2.2.8.5 Interference with barium Rats Rats were fed diets with 10% alginate (3 different types). At day 3 or 4 on diet the animals received an oral, i.p. or s.c. dose of 133Ba. The retention of barium in the carcass after oral administration was reduced 4 to 8 times with the different types of alginate. Four days after parenteral administration of radiolabelled barium, the barium content of the carcass was 5-12% lower than in controls accompanied by a small increase in faecal excretion of the marker (Sutton et al., 1972). 2.2.9 Observations in humans Six healthy adults were given 8 g of sodium alginate daily for seven days without untoward effects (Millis & Reed, 1947). Three patients whose clinical condition warranted sodium restriction were given oral doses of 15 g of alginic acid three times daily for seven days. A slightly increased faecal sodium and potassium excretion was noted, but no changes in plasma electrolyte concentration (Feldman et al., 1952). Six patients with essential hypertension were given daily doses of 45 g of alginic acid containing 10% of potassium alginate for five to nine weeks and three patients in an oedematous state were given the same dosage for about a week. It was well tolerated and produced no gastrointestinal disturbance (Gill & Duncan, 1952). Five healthy male volunteers received 175 mg sodium alginate/kg bw/day for 7 days, followed by 200 mg/kg bw for a further 16 days. The daily doses were consumed in three measured portions at intervals each day. The portions were prepared by adding the weighed aliquots of sodium alginate by rapid stirring to 220 ml cold distilled water. The hydrocolloid was then allowed to hydrate for 24 h to a thick, but fluid gel to which each volunteer added a predetermined amount of orange juice prior to consumption. The treatment period was preceded by a 7 day initial control period during which a daily amount of orange juice, equal to that to be taken later, was consumed. During the treatment period enquiries were made with respect to apparent allergic responses. At day 3 of the initial control period, on the last day of the 23 day treatment period and on the last day of the 7 day recovery period the following parameters were examined; fasting blood glucose, plasma insulin, breath hydrogen concentrations, haematological parameters (Hb, Ht, MCV, MCH, MCHC, Er, Leu, Diff, platelets) and biochemical parameters (Na, Cl, K, CO2, urea, LDH, AST, bilirubin, alk. phosphatase, phosphate, Ca, protein, albumin, creatinine, urate, lipids, cholesterol, HDL cholesterol and triglycerides). Routine urinalysis was carried out during the initial control week and during the third week of treatment. Five day faecal collections were made during days 2-6 of the initial control period and during days 16-20 of the treatment period. Faecal transit time, wet weight, dry weight, water content, pH, occult blood, neutral sterols, fat, volatile fatty acids and bile acids in faeces were determined. No allergic reactions were reported nor observed. Sodium alginate acted as a bulking agent of moderate efficiency as indicated by a significant increase in faecal dry and wet weight and an increase in water content of faeces without a significant change in transit time. Faecal pH remained normal. Total faecal volatile acids increased in four volunteers but decreased in one. No changes in faecal total and individual neutral sterols or in total and individual bile acids were seen. Haematological, biochemical and urinalysis parameters did not show significant changes with the exception of some parameters of one volunteer who suffered from influenza (Anderson et al., 1991). Two-hundred-and-eight workers who are exposed to dust from dried milled seaweed and pure alginate compounds in an alginate factory were examined for pulmonary hypersensitivity. Fifteen out of these 208 workers showed symptoms definitely related to dust exposure at work. Serological tests showed that 8 of the 15 workers with definite symptoms and one worker without definite symptoms had precipitating antibodies to prepared extracts in their serum. Chest X-rays of these 16 workers were normal. Twelve workers with either evidence of work related respiratory symptoms or precipitating antibodies in their serum or both (3 out of 12) were exposed to an atmosphere artificially contaminated with raw seaweed dust for a maximum of one hour. Measurements of pulmonary function were made before, immediately after, and 1, 3, 5 and 24 h after exposure. A significant reversible deterioration in pulmonary function was seen as shown by an acute and sometimes severe airway obstruction, followed by a delayed loss of lung volume with reduction in transfer factor (Henderson et al., 1984). 3. COMMENTS Three limited long-term dietary studies, one in mice and two in rats, provided no indication of a carcinogenic effect of alginates. Neiher an in vitro nor an in vivo genotoxicity study showed any genotoxic activity. No effects on the reproduction of rats were observed, but the experimental design of the study was limited. A long-term study in mice using only a single dose level of 25% sodium alginate in the diet showed a clear effect (soft stool, distended caecum, decreased growth and deposition of calcium in the pelvis of the kidney). In a 90-day study in rats, 15% sodium alginate in the diet resulted in an enlarged, distended, heavy caecum, a papillomatous appearance in the urinary bladder and calcium deposits in the renal pelvis and/or renal papilla. A slight decrease in growth was seen in only one short-term experiment with rats at the 10% level, but the effects were not specific and were also seen with other poorly absorbed compounds. Recent studies have shown slight interference with the absorption of a number of minerals. 4. 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See Also: Toxicological Abbreviations Alginic acid and its ammonium, calcium, potassium and sodium salts (WHO Food Additives Series 5)