Thickening agents are often used in the treatment of dysphagia to improve bolus control and prevent swallow aspiration. They bind with water to increase bolus viscosity, slowing the entrance of thickened fluids into the pharynx, which may reduce the risk of aspiration(1)
Commercially produced starch- and gum-based thickening agents have an important role in clinical practice. Gum-based thickeners represent a newer generation of thickening agents and are increasingly popular amongst healthcare professionals (HCPs) due to their clarity, stability, and resistance to amylase.
However, there are certain clinical contraindications for gum-based thickeners, supported by clinical research. Additionally, there is a percentage of patients who will benefit from and/or prefer starch-based thickeners. Finally, it’s important to give patients autonomy when it comes to choosing their thickening agent.
This article is written from a dietitian’s perspective and has been sponsored by AYMES International. It aims to encourage HCPs to think about their own clinical practice when working with patients who use commercially produced thickening agents for dysphagia.
|Viscosity||High viscosity across a range of temperatures||High viscosity across a range of temperatures|
|Stability||May continue to thicken over time||Stable viscosity over time|
|Consistency||Susceptible to amylase digestion||Amylase-resistant|
Thickening agents are often used in the treatment of dysphagia to improve bolus control and prevent swallow aspiration. They bind with water to increase bolus viscosity, slowing the entrance of thickened fluids into the pharynx, which may reduce the risk of aspiration(2)
It’s important to recognise that gum-based thickeners are widely used in clinical practice and are tolerated by the majority of patients. However, there may be some clinical contraindications in a minority of patients. This article focuses on evidence relating to xanthan gum as it is one of the main ingredients in most gum-based thickeners.
Animal studies have found that large doses of xanthan gum can induce soft stools with increased frequency (3, 4). However, findings from animal studies cannot be applied directly to humans. Additionally, these studies used extremely high doses of xanthan gum, which humans are unlikely to consume from an oral diet alone.
One small human trial found that moderate doses of xanthan gum (15g/day) caused similar digestive symptoms in humans over 10 days in 18 healthy men (5). The researchers concluded that xanthan gum has a “highly efficient laxative effect” as it significantly increased stool output, frequency of defecation, and flatulence, whilst having variable effects on gut transit time. The same study found that healthy volunteers were asymptomatic if they consumed less than 15g of xanthan gum per day, suggesting that at small doses, xanthan gum is unlikely to cause adverse effects.
The European Food Safety Authority (EFSA) re-evaluated the safety of xanthan gum as a food additive in 2017. They found that repeated oral intake of up to 214 mg/kg of body weight per day (approximately 12.8g xanthan gum per day for a 60kg individual) for 10 days was well tolerated amongst most adults. Whilst some individuals experienced ‘undesirable abdominal discomfort’, this was not considered to be an adverse effect. The EFSA concluded that there are no safety concerns for the use of xanthan gum as a food additive at concentrations reported by the food industry (6).
The table below provides an estimation of how much thickening agent a patient would consume at different IDDSI levels. It is not possible to accurately estimate how much xanthan gum a patient would consume from the thickening agent as manufacturers do not provide this information. However, it’s likely that patients on higher IDDSI levels could be consuming more than the amounts of xanthan gum used in the trials above. Given its laxative effects at high doses, this could be problematic for patients with loose stools due to a pre-existing condition such as irritable bowel syndrome (which affects around 10-20% of the general population (7) or lactose intolerance.
Table 1: Amount of thickening agent consumed in 2 litres of fluids at different IDDSI levels*
|Level 1||Level 2||Level 3||Level 4|
|Number of scoops added (scoop size:1.2g)||1||2||4||6|
|Amount of thickening agent consumed in 2 litres of fluid||12g||24g||48g||72g|
*Calculated using a market-leading gum-based thickening agent (Resource ThickenUp Clear)
The dosage of xanthan gum should also be carefully considered in those taking medications and supplements which are known to have a laxative effect. These may include (but are not limited to magnesium (8), laxatives, metformin (9), certain antibiotics (10), chemotherapy drugs (11), cholesterol-lowering agents (12), and specific thyroid hormones (13). If there are contraindications for using xanthan gum, a starch-based thickener may be more appropriate.
NICE Clinical Guideline CG32 (Nutrition Support for Adults) states that: “People with dysphagia should have a drug review to ascertain if the current drug formulation, route and timing of administration remains appropriate and is without contraindications for the feeding regimen or swallowing process” (14).
The Francis Report highlighted the importance of giving people food and fluid in a form they can safely consume, and of delivering care based on the needs and choices of patients (16). It forms part of NICE Clinical Guideline CG32 (14).
Anecdotal reports from HCPs suggest that some patients, particularly those with a learning disability, prefer starch-based thickeners in the long-term. Additionally, patients who are used to taking traditional starch-based thickeners may find it difficult to cope with switching to newer gum-based products after long-term usage. It all comes back to patient choice –- giving patients autonomy and empowering them to make their own decisions (where appropriate) about their choice of thickening agent.
In conclusion, both gum-based and starch-based thickeners have important roles in clinical practice. Whilst gum-based thickeners are becoming increasingly popular amongst HCPs and patients, there may be some clinical contraindications in a minority of patients. Research suggests that xanthan gum may have a laxative effect when consumed in large amounts (>15g/day), which could be problematic in patients with pre-existing digestive conditions or those who take certain medications or supplements.
It is important for speech and language therapists and dietitians to work together as part of a wider multi-disciplinary team to establish which type of thickener would be most appropriate for the patient. Regularly reviewing patients is important to monitor for any adverse effects relating to their thickening agent. In some instances, switching to a starch-based thickener may be most appropriate. Finally, this article has reiterated the importance of giving patients autonomy when it comes to choosing a thickening agent that meets their individual requirements.
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