Solubility of betaine
Available products for betaine supplementation to animal feed consist either of anhydrous betaine sources or betaine in hydrochloride form (betaine HCl). Furthermore, anhydrous betaine products can either be of synthetic origin or naturally derived from sugar beets.
Both molecular forms – anhydrous betaine and betaine HCl – are fully soluble in water. The solubility of anhydrous betaine is higher compared to betaine HCl (157g versus 60g in 100mℓ, respectively). Still, as you only need 1,666mℓ water to dissolve 1g of betaine HCl, in practice all supplemented betaine HCl will easily be dissolved in the intestinal digesta after ingestion. The solubility difference is therefore practically irrelevant.
When betaine HCl is dissolved, dissociation will occur. Betaine has a pKa value of approximately 2,33 and thus at physiological pH levels, the molecule
will be present in dissociated form as zwitterion (a molecule that has both a positive and negative charged region).
In vitro research confirmed that betaine molecules appeared under identical form under simulated gastric conditions, independent of the source (anhydrous or HCl). As the same molecular form will enter the small intestine, where betaine can be absorbed by the present transporters, the nutritional value of both betaine sources will be equal.
In a trial with pigs, it was demonstrated that absorption of betaine is very rapid. Within 20 minutes of a single oral supplementation of 3g betaine from either betaine anhydrous or betaine HCl, an increase in betaine in the blood was measured. For both sources of supplemented betaine, a very similar betaine serum profile could be observed, although variability between individual pigs can be high (Figure 1).
Statistical analyses of pharmacokinetic parameters showed no differences between both sources. Consequently, the nutritional value of betaine from betaine HCl can be considered equal to anhydrous betaine (natural or synthetic).
