how do you know if a food healthy or not

we gust saw on a movie that mcdonald fries can last for a month without getting mildoo.some halthy foods are brocallie,corn,greenbeans,. some unhalthey food are cake,chips,soda,grease,salt,candybars,.did you know if every body ate haelthy the earth would be haelthy but it not good to eat haelthy every day because are body need sodium. by khalil thompson@ ms,vibbert cla$$ room .com<<<<<>>>>>>