The first gulps of water I have after a long run are delicious. They’re refreshing and life-giving, yes, but the water also tastes good. It actually tastes sweet, to be more precise.
Which, when I stopped to think about it mid-gulp one day, I found odd. Isn’t water a famously, um, neutral flavor? And why does it taste different after one of my long runs?
I’m not imagining things: A systematic review of literature on the connection between taste and exercise found that sweet taste intensity and sensitivity increases after acute exercise. However, Jason Machowsky, an exercise physiologist and registered dietitian at the Hospital for Special Surgery in New York City, says why that’s actually happening is not so clear.
“There doesn’t seem to be any well-researched reasons for it,” Machowsky says. “There are, however, a lot of theories.”
The first hypothesis has to do with the idea of “heightened sensitivity.” Machowsky explains that there are minerals in water that do taste sweet to some people, and so after a strenuous workout, those minerals might taste even more noticeably sweeter.
In a related (but semi-gross) explanation, your post-workout water could be dredging up old food particles or residue in your mouth that you’re re-tasting in a more dramatic way, thanks to that sensitivity.
Or something else could be going on entirely. You may have heard of “ketosis,” the metabolic state in which the body burns fat instead of carbohydrates (achieving ketosis is the aim of the keto diet). This state occurs when glycogen stores (which come from carbohydrates) are depleted, so the body turns to fat for energy. What, besides the keto diet, can cause someone to run through their glycogen stores and use fat instead? Intense, prolonged exercise.
Being in ketosis can have some physical manifestations, including—wait for it—sweet breath.
“A ‘sweet’ flavor or aroma to [the] breath is a byproduct of the breakdown of ketones for energy,” says Machowsky. So drinking water and noticing a sweet flavor could come from the interaction of water and…