cause negative effects on your body!!! CHECK THE UPPER LIMITS of vitamins and track your intakes. DO NOT take 5 different multivitamin pills and assume that your body will just be in better shape due to this. Whatever your body does not need, it will get rid of, and in some cases, will end up causing side effects.
l (again I say average since everyone has different things that work and don't work for them). I personally am a big fan of taking a multivitamin a day and taking a Biotin tablet every 3 days in place of the multivitamin. This has helped both my hair and nails grow healthier!