Scientists studied how different thickening agents affect swallowing in healthy adults. They had 30 people drink thickened liquids of varying thickness levels while recording videos of their swallowing. The research found that thicker liquids stay higher in the throat and help the voice box close longer, which may make swallowing safer. Interestingly, some thickeners made the liquid more stable and easier to control than others. This information is important for people who have difficulty swallowing and need thickened liquids as part of their treatment.

The Quick Take

  • What they studied: How different thickening products affect the way liquids move through the throat when people swallow, and whether thicker liquids are safer to swallow.
  • Who participated: Thirty healthy adults with no swallowing problems participated in the study. They drank small amounts of thickened liquids at different thickness levels.
  • Key finding: Thicker liquids stayed higher in the throat and caused the voice box to close for longer periods, which suggests they may be safer to swallow. Some thickening products created more stable, controlled liquid movement than others.
  • What it means for you: If you have swallowing difficulties, your doctor may recommend thickened liquids. This research suggests that thicker liquids may offer better protection, and the type of thickener used matters. Talk to your healthcare provider about which thickener might work best for you.

The Research Details

Researchers recruited 30 healthy adults and had them swallow small amounts of liquid (about 2 teaspoons) that was thickened using five different commercial thickening products. Each product was tested at four different thickness levels, ranging from slightly thick to very thick. While the participants swallowed, special X-ray videos (called videofluoroscopic swallowing studies) recorded exactly what happened in their throat. The researchers measured where the liquid went, how long the voice box stayed closed, and how the liquid moved through the throat.

Understanding how different thickeners work is important because people with swallowing problems rely on thickened liquids to stay safe. If we know which thickeners work best and how they affect swallowing, doctors can make better recommendations. This study used healthy adults as a baseline to understand normal swallowing patterns with different thickeners.

This study used objective measurements from X-ray videos rather than just asking people how they felt, which makes the results more reliable. The researchers tested multiple thickening products at multiple thickness levels, providing comprehensive information. However, because the study only included healthy adults without swallowing problems, the results may not directly apply to people with actual swallowing difficulties.

What the Results Show

As liquids got thicker, they stayed higher in the throat. Very thin liquids went down into the lower throat (hypopharynx) quickly, while very thick liquids stayed in the mouth or upper throat areas. This positioning may help prevent liquids from going into the airway. The voice box (larynx) closed for longer periods when people swallowed thicker liquids. At the thinnest level, the voice box closed for a shorter time, but as thickness increased to levels 3 and 4, the closure time increased significantly. This longer closure time may provide better protection of the airway during swallowing. Different thickening products behaved differently even when they had the same thickness level. Gum-based thickeners (like ThickenUp Clear) created more cohesive, stable liquids that moved more predictably through the throat. Starch-based thickeners produced less stable liquids that didn’t hold together as well.

The shape of the liquid bolus (called the bolus aspect ratio) remained relatively consistent across all thickness levels and thickening agents, suggesting that the overall shape of the swallowed liquid doesn’t change much regardless of which thickener is used. This finding indicates that thickness level and thickener type primarily affect how the liquid moves and where it goes, rather than changing its shape.

This research builds on existing knowledge that thicker liquids are generally safer for people with swallowing problems. The new contribution is showing that the specific type of thickener matters—not all thickeners work the same way even when they reach the same thickness level. Previous research suggested this might be true, but this study provides detailed evidence using X-ray imaging.

The study only included healthy adults without swallowing problems, so the results may not apply to people with actual swallowing difficulties. The sample size of 30 people is relatively small. The study used very small amounts of liquid (10 mL or about 2 teaspoons), which may not reflect how people swallow larger amounts. The research was conducted in a laboratory setting with X-ray equipment, which is different from normal eating situations.

The Bottom Line

For people with swallowing difficulties: Work with a speech-language pathologist or doctor to determine the appropriate thickness level for your needs. Consider trying gum-based thickeners (like ThickenUp Clear) if available, as this research suggests they may provide more stable and controlled liquid movement. Start with the thickest consistency recommended by your healthcare provider and adjust based on your comfort and safety. Moderate confidence: These findings come from healthy adults, so individual results may vary.

People with swallowing difficulties (dysphagia) should care about this research, including those recovering from stroke, with neurological conditions, or with other medical conditions affecting swallowing. Healthcare providers who recommend thickened liquids should be aware that thickener type matters. Family members helping care for someone with swallowing problems may find this information useful. Healthy people without swallowing problems don’t need to change their diet based on this research.

If you’re starting thickened liquids, you should notice any safety improvements (like reduced coughing or choking) within the first few swallows. The benefits of using the right thickener and thickness level are immediate, not something that develops over weeks or months.

Want to Apply This Research?

  • If using a nutrition or health tracking app, log the type of thickener used (brand name), thickness level, and any swallowing symptoms (coughing, choking, difficulty) at each meal. Track this daily to identify patterns and share with your healthcare provider.
  • If your app supports meal logging, add a field to record which thickening product you’re using and at what level. Set reminders to use the specific thickener recommended by your doctor, and note any changes in how comfortable swallowing feels with different products.
  • Over 2-4 weeks, track which thickener and thickness level works best for you by monitoring swallowing comfort and safety. Share this data with your healthcare provider at your next appointment to optimize your thickened liquid prescription.

This research describes how thickening products work in healthy adults and should not be used to self-diagnose or self-treat swallowing problems. If you experience difficulty swallowing, coughing while drinking, or choking, consult a healthcare provider immediately. Thickened liquids should only be used under medical supervision and as recommended by a speech-language pathologist or physician. Individual swallowing needs vary, and what works for one person may not work for another. Always follow your healthcare provider’s specific recommendations for liquid thickness and thickening products.