Does toothpaste break a fast?

Brush as usual

There's no reason to skip brushing while you fast. Brush twice a day with fluoride toothpaste and spit it out: toothpaste isn't meant to be swallowed, fast or no fast. Your fast is ended by what you eat and drink, not by what passes through your mouth and leaves again.

Brushing can even help. Many people brush after their last meal of the day, and it makes a handy signal that the kitchen is closed and your fast has begun.

Mouthwash, floss and the rest

Product	While fasting
Toothpaste	Fine: spit it out
Mouthwash, with or without alcohol	Fine: rinse and spit, never swallow
Floss, interdental brushes, tongue scrapers	Fine
Sugar-free gum	An occasional piece is fine: see gum
Breath mints	Many contain sugar: choose sugar-free ones, or have a glass of water
Lip balm	Fine

Even the World Health Organization's guideline against sweeteners leaves toothpaste and other personal care products out of its advice ².

MYTH

If you can taste something sweet, your fast is over.

FACT

Taste isn't what ends a fast; calories are, especially from sugar and protein. In a British trial, tasting sucralose and spitting it out didn't change insulin or gut hormones ¹.

Fasting breath, and why brushing helps

Many people notice their breath changes on a fast, especially a longer one. Brushing, cleaning your tongue and drinking water through the day all help, and none of them break your fast. Our answer on bad breath while fasting explains why it happens and what else helps.

If you fast for religious reasons

Religious fasts have their own rules, and views on toothpaste and mouthwash differ between traditions and scholars. Follow the guidance you trust. Our page on Ramadan and intermittent fasting explains how the two compare.

What does break a fast

Anything you eat or drink with calories, especially sugar or protein: juice, milk beyond a splash, protein shakes and snacks of any size. Water, black coffee and plain tea are fine. Our guide to what breaks a fast goes through each one with the research behind it.

Unsure about something else? Ask two questions: does it have calories, and do you swallow it? If the answer to both is yes, keep it for your eating window.

Sources

1. Ford HE, Peters V, Martin NM, et al. Effects of oral ingestion of sucralose on gut hormone response and appetite in healthy normal-weight subjects. Eur J Clin Nutr. 2011;65(4):508-13. doi.org/10.1038/ejcn.2010.291
2. World Health Organization. WHO advises not to use non-sugar sweeteners for weight control in newly released guideline. 15 May 2023. www.who.int/news/item/15-05-2023-who-advises-not-to-use-non-sugar-sweeteners-for-weight-control-in-newly-released-guideline