14792
In a randomized , double - blind study , healthy middle - aged participants received a dark chocolate drink mix standardized to contain 500 mg , 250 mg or 0 mg of polyphenols ( placebo ) in a parallel - groups design .
 Chemical: polyphenols
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: polyphenols