Guinness had that daft reputation for a long time, that it was "full of iron". My gran had a heart attack in her mid nineties, we visited her in hospital as kids, she was in bed drinking Guinness to "build her stength back up"
File it along with "spinach is full of iron" that stemmed from some scientist misplacing a decimal point, so for decades people thought spinach had ten times as much iron as it actually does. We'd never have had Popeye only for that mistake