Reader Question: Can I have soy sauce before colonoscopy?

“Trying to stick to the colonoscopy prep rules—does anyone know if a little soy sauce is allowed in clear broth? Since it’s very dark, I’m not sure if it’s OK or not.”

A: This is an excellent question because the rules around “clear liquids” can get confusing.

The concern is mainly about dark or red liquids, such as grape juice, cola, or tomato-based products, that can stain the lining of the colon or make it harder for the doctor to see clearly.

Soy sauce itself is not a clear liquid. It’s dark-colored and opaque, so if you drink it straight, it wouldn’t meet the “clear liquid” standard your doctor expects during colonoscopy prep.

However, a small amount of soy sauce added to broth as flavouring is usually okay as long as the broth remains transparent. For example, a light splash in chicken or vegetable broth for flavor is fine. If you add so much soy sauce that you can no longer see through the broth, it is no longer safe for consumption.

In conclusion, do not drink soy sauce alone; a dash in clear broth to improve taste is generally acceptable. Just don’t overdo it so the broth stays light and see-through.

Source:

Glen Garry Gastroenterology https://glengarrygastroenterology.com.au/wp-content/uploads/2023/05/Oliver-Duncan-Bowel-prep-instructions-AM-1.pdf