Who do you think would have more artery clogging in the heart: (A) a group of sedentary, overweight men; or (B) a group of men who are slightly older, much leaner, and have run at least one marathon annually for 25 years?
The sample size isn’t terribly large, and while the study says they couldn’t pinpoint why the plaque was happening. But from numerous people I’ve spoken to, there’s a percentage who run marathons/etc but eat poorly. Those that eat poorly, due so because they are looking to consumer lots of calories, salt, or just “reward” themselves with nutritionally poor food.
What about the water? J. Kenji López-Alt from SeriousEats (and previously Cook’s Illustrated) wrote about performing a test concerning the effects of water on pizza crust. They used multiple bottled waters, with different levels of dissolved solids as well as NYC tap water in the introduction of his new book. His panel of judges weren’t able to detect a significant difference between any of the crusts made with the different waters. At this point, I think it’s safe to say this is a myth or at least a very large degree of self-induced bias.