If you have a well balanced diet there is no need for any supplements unless suffering from deficiency. Moreover no supplements should be taken without advice of a health professional as it can interfere with the medicine you are taking and excess of any nutrient is harmful.
Multivitamin Will help you if indicated. Yes taking Multivitamin for too long can cause side effects. Just Take for 10 days in a month on alternative days. And give gap for 1 month. A to Z Capscule.