Making the assumption of course that individuals consume every item they purchase. I can just hear the doctor now, "Sir, we need to point out that tampons should only be used as feminine care products. As a man, you could seriously injure your health using them." "and about that baby formula, it's very high in calories and will contribute to weight gain, you need to stop using it."
The surgeon on Cavuto pointed out exactly the mistakes and wrong conclusions that can be reached because people don’t just purchase items from just themselves...
Years ago, I read a futurist report from a computer company working with data analysis. They gave a case study called "The Pregnant Gay Man" to illustrate that assumptions can be wrong, and suggested that a gay man could buy a lot of stuff about pregnancy from Amazon to throw his sister a baby shower, and the purchases shouldn't end up in his data profile -- but there would be little way for a computer to actually know why he bought that stuff or to screen it out.
Of course, that was years ago, before there actually was a preganant gay man.