it's not a placebo because it's not a drug. It's a mega-multi-vitamin. It certainly does the trick.
Uh, as far as I understand you can talk about a placebo effect even if you're not talking about drugs. So, say that I had depression and heard that eating lots of pizza would help me feel better, so I ate lots of pizza and convinced myself it was working and started to feel happier. That wouldn't be a drug, but it would be a placebo effect. Right?