The science is legit here. They're teaching us this in med school.
The reason that everyone reacts to drugs differently is precisely because of these Cytochrome P450 enzymes. Drug companies will abandon a drug that interacts with certain Cyt.P450s because there is a huge variation in how people will respond to them. Some will overdose on just a very small quantity and others will require monstrous doses to have any effect. The more active your particular enzyme, the larger the dose of the drug you're going to need. The less active, naturally, the smaller the dose. Listen to your body; it will tell you what's going on.
I'll take help wherever I can ge it.