Carrageenan: The effect of molecular weight and polymer type on its uptake, excretion and degradation in animals

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A variety of τ-, κ- and λ-carrageenans was given to guinea-pigs, monkeys and rats, either in the drinking-water, by gavage or in the diet. Faecal and liver samples were examined qualitatively by gel electrophoresis, to determine any changes in the apparent molecular weight of carrageenans after administration. Quantitative measurements of carrageenans were carried out on samples of liver and urine. That there was little or no absorption of carrageenans of high molecular weight was evidenced by the absence of carrageenan from the livers of guinea-pigs or rats or from the urine of guinea-pigs or monkeys. By contrast, substantial amounts of carrageenan were found in the livers of guinea-pigs and rats given low-molecular-weight carrageenans (M n ⩽ 40,000). Intermediate amounts of carrageenan were found in livers of animals given carrageenans ranging in M n between 40,000 and 150,000. Urinary excretion of carrageenan was limited to low-molecular-weight material (M n ⩽ 20.000). Qualitative and quantitative evidence indicated that there was an upper limit to the size of carrageenan molecules absorbed, but estimates of this upper limit ranged from 10,000 to 85.000 depending upon the analytical approach. Absorption of carrageenan from the drinking-water may differ qualitatively from absorption from the diet. Analysis of faecal samples by gel electrophoresis showed that degradation of high-molecular-weight carrageenan had occurred, either in the gut or in the faeces.