I'm not sure that science can, strictly speaking, tell us what constitutes "harm".
There are certainly senses of the word that are subjective (harms to integrity, or the soul, or whatever). I think in general "harm" is not a word that strictly speaking has an objective meaning, even though admittedly there are senses on which there is so much intersubjective consensus that it might seem that way.
I don't really agree that there are cases where science tells us "this will harm you", and we cannot help but respond in the subjective frame. Science can tell me that (say) drinking a glass of wine with dinner every night might slightly lessen my life expectancy, and someone might describe that as "harm"; but that does not force any moral response from me, nor does it mean that "science tells us we shouldn't drink alcohol".
