Is apple cider vinegar as good for health as it sounds?

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Each morning at breakfast, my partner gives me orange juice that tastes more sour than expected. One day, she explained that she adds apple cider vinegar to improve my health. As a former primary schoolteacher she swears by the stuff. She tells me she kept apple cider vinegar in the staff room so that when children became ill with diarrhoea and vomiting, she could take it immediately to protect her from the illness. I was sceptical about yet another immune-boosting miracle ingredient. Apple cider vinegar is a natural product made of fermented apple juice that has gone sour. Apparently, the...