for some people they are, and it is generally believed that a multi-vitamin may be a ‘back-up’ against deficiencies even though this is debatable.
I recommend that people get a check-up where blood levels determine whether there are deficiencies, and then take supplements according to directions. I am particularly adamant about this when people take prescription drugs as some can interfere with absorption.
Only if there is a specific deficiency which it has been determined by a blood test and a treatment has been recommended by a physician. People tend to spend big $$ in over the counter vitamins and supplements without even knowing if they really need them. Most of the recommended vitamin requirements we can get them by simply eating a balanced diet. Each person is different and unless they have a medical condition which depletes them form a specific vitamin(s), they really don’t need any extra supplementation. Also, with so many brands and types of vitamins out there, it’s almost impossible to figure out which ones are the best and most efficient.
In general I have no concerns with multivitamin-mineral supplements that provide no more than 100% of any nutrient. Most important, in my opinion, is generally consuming a sensible diet that follows the guidelines of the ADA’s Food Guide Pyramid.
As suggested, the “need” for supplements is a topic of frequent debate. If you’re going to take any supplement I agree with Karin that a blood test and a discussion with your physician concerning the need for supplements is an important step.