Sentence:  In man the normal level of <WSD>iodine</WSD> in the diet and the level necessary to prevent development of goitre is about 100 | mg per day . 
Meaning of the word marked with <WSD> tags:  a nonmetallic element belonging to the halogens; used especially in medicine and photography and in dyes; occurs naturally only in combination in small quantities (as in sea water or rocks)