Question about B6

Does a surplus of Vitamin B6 force your body to produce extra seratonin to get rid of it, or does your body intentionally (so to speak) put the surplus to good use?

I wonder this because I have a policy of not taking any substance that alters your brain chemistry in any unnatural way. That is, if a drug forces your brain to produce serotonin, then I don’t want take it, but if it’s merely providing nutrients that are made use of “voluntarily” (again, so to speak), then I’m fine with taking it.