Wait 20 to 30 minutes after eating (especially acidic foods) before brushing your teeth, to allow saliva to neutralize the oral pH and avoid mechanically wearing down the temporarily weakened enamel.

noli's read

The basic physiological explanation is entirely accurate: after a meal, particularly an acidic one, oral pH drops temporarily, which momentarily softens the superficial mineral layer of the teeth. For this reason, waiting 30 minutes is a standard recommendation supported by exploratory in vitro studies, such as that of Wiegand et al. in 2008. However, recent scientific syntheses have nuanced this dogma. Indeed, a meta-analysis by Hong et al. (2020) compiled several in vitro and in situ studies and concluded that delaying brushing after acidic exposure did not provide a statistically significant reduction in wear on human enamel compared to immediate brushing. This research reveals that the benefit of waiting is observed mainly on enamel of bovine origin, often used during laboratory tests, but does not clearly transpose to humans. The analysis instead highlights that the true protective factor lies in the intake of strengthening minerals via toothpaste during brushing. To optimize daily hygiene without stressing over timing, a simple rinse with water or the use of chewing gum after a meal remains an excellent alternative practice to help saliva perform its natural regulatory work.

the sources

No named source held this one up — that absence is part of the verdict.