X-Message-Number: 10037
Date: Sat, 11 Jul 1998 09:02:11 -0700 (PDT)
From: Doug Skrecky <>
Subject: metabolism of sugar alcohols

Quote from (Regulatory Toxicology and Pharmacology 24: S198-S205 1996):

  "Erythritol is a tetritol, i.e. a 1,2,3,4-butanetetrol. As such,
erythritol ranks in the homologous series of the monosaccharide sugar
alcohols between the only existing triitol (glycerol) and the four
stereoisomeric pentitols (xylitol, ribitol, and d- or l-arabitol). Among
the three stereoisomeric tetritols, erythritol (syn.: meso-erythritol) is
the one which is optically inactive (the other two being d- and
  Glycerol has a small molecular volume; it is therefore readily, and thus
completely, absorbed from the intestinal tract. The pentitols, on the other
hand, have a larger molecular volume; their uptake by passive diffusion -
through hydrophilic "pores" of the cell membranes (transcellular pathway)
and/or through the "tight" junctions between the intestinal epithelial
cells - proceeds therefore at a much lower rate and thus is incomplete. For
erythritol, which has a molecular volume between that of glycerol and the
pentitols, an intermediate diffusion rate is to be expected. Experiments of
others, which were published after completion of this study, indicate
indeed that about 65-90% of an ingested U-14C-erythritol dose is absorbed
by rats.
  The absorbed portion of monosaccharide sugar alcohols is metabolized
rather quickly (glycerol, ribitol, xylitol, sorbitol), slowly (l-arabitol),
or not to any relevant extent (erythritol, d-arabitol, mannitol). Because
of their hydrophilicity and chemical inertness, absorbed yet not
metabolized sugar alcohols are readily excreted with the urine in unchanged
form. The unabsorbed fraction of sugar alcohols is fermented in the large
intestine by the gut microflora to short-chain fatty acids which are
absorbed almost completely and are metabolized in the body by ordinary
metabolic pathways."

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