Observational studies in human nutrition are a waste of money: polyphenol content of food and hypertension

http://www.mdpi.com/2072-6643/9/10/1069/htm

Not to mention polyphenol cocktail in cancer:
http://www.mdpi.com/2072-6643/8/9/552/htm
Studies on cancer cell culture are of poor value if one considers the high number of factors which affect the fate of cell culture in vitro.