Research has been showing that modified corn-starch based thickeners are not ideal for thickened liquids in patients with dysphagia and aspiration. These corn-starch based thickeners are broken down with amylase in the saliva. This causes the thickened liquid to be much thinner as it interacts with saliva. Industry is moving towards Xanthan gum based thickeners.
Additionally, Rheology characteristics of the non-newtonian fluid come into play. The thickened liquid has shear-thinning characteristics as force is placed on them and they are stripped through the mouth and throat. This occurs with xanthan gum thickeners, but to a lesser degree supposedly than cornstarch based thickeners.
Xanthan gum is resistant to the salivary amylase and passes through the upper phase of the digestive tract intact. However, per the article in the link below, Cichero (2013) noted how xanthan gum requires bacteria/microflora of the large intestine to break it down. I only know of two studies on the bioavailability of a liquid thickened with xanthan gum. Sharpe et al (2007) in Dysphagia journal showed good bioavailability, but tested rats and "healthy mature human guts." Hill et al (2010) in second link below showed good bioavailability, but in only a proof of concept/single subject case study of a healthy human.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3660277/
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2846329/
**I wonder about our critically ill dysphagic patients, particularly those with many colon issues (i.e., antibiotics killing off good bacteria, C-Diff, and patients with colonic resections/colostomies).
Can these patients break down the xanthan gum to make the fluid readily bioavailable?
Does the xanthan gum get broken down at all prior to the large intestine?
Thank you Dr Steele for following this.
Below, I linked two of my blogs related to thickeners.
I was discussing further with my chemist father. (Hope more scientists will add.)
Xanthan gum (xanthomonas campestris bacteria) is a complex non-starch polysaccharide with long Tri-saccharide side chains. (Usually grown on glucose as the substrate).
Versus guar gum, which has short side branches and is not a trisaccharide. Is guar gum better as a thickening agent?
Xanthan gum binds to water efficiently and can aide in passing stools, but some people react with bloating. But maybe it binds too efficiently??
Xanthan gum is also sometimes derived from corn, wheat, dairy or soy. Potential allergens? Residual wheat gluten? A strain of xanthomonas bacteria was added to whey, as this byproduct of cheese production is readily available. Researchers developed X Campestris that grows on whey/lactose rather than glucose. Again, an allergen? What if we put our patient on a thickened liquid that causes an allergic - would people even realize that it came from the thickener powder?
We need the best thickening agent for liquids for patients with dysphagia. As we are switching more and more from corn-starch to xanthan gum or other products, I feel the speech-language pathologist must stay informed when giving recommendations.
Ideal product:
Salivary enzyme resistant (amylase, lysozyme), but then readily break down in the stomach, allowing the fluid to be immediately bioavailable - Even in the presence of altered stomach pH, as most of our patients are on acid suppression therapy. Of course, the patients want it to be clear, tasteless, and to not leave their mouth feeling dry/sticky. Pre-thickened liquid juice and milk boxes should not have sugar added. The Endocrinologist always notices when a diabetic patient gets put on thick liquids! The thickener should not bind with the watery aspects of saliva, as stimulated saliva flow becomes more watery. Let's not strip out the saliva with the liquid.
June is National Dysphagia Awareness month - let's push this and research this for our patients!
http://www.swallowstudy.com/?p=850
http://www.swallowstudy.com/?p=593
Hi, I don't know this literature, but I think your interrogation is important. Digestive tolerance of thickeners seems to be different along people.
I observed that some healthy subjects experimented digestive disorders from abdominal pain to diarrhea after testing thickened liquids (experimental condition to elaborate a dilution protocole for nurses).
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