There answer is not necessarily a simple *Yes* or *No*.

Way too little of a vitamin is a terrible thing, and way too much can be just as bad, although you must reach rather high levels to contract vitamin intoxication. A *what's the harm* attitude towards multivitamins is arguably defensible, as you're not running a risk of vitamin intoxication from following the recommended dosage. It rather boils down to whether or not you're willing to spend the money, and go through the daily routine, and it's not at all obvious that you should need to.

Vitamin supplements are all about avoiding a vitamin deficiency. There really is no added benefit to getting *more* vitamins once you're at sufficient levels. The trick is that it's not that easy to keep track of whether or not you are. The rule cannot be generalized into saying "Healthy adults don't need vitamin supplements, because in order to be healthy, you must not have a vitamin deficiency." You're not likely to catch scurvy unless you're doing something terribly wrong, that's not what this is all about. There can be more subtle effects of small vitamin deficiencies. Vitamins can help you fend off other diseases, for instance:
> Vitamin D from a multivitamin or single supplement can lower the risk of colon and possibly many other cancers. <sup>[* harvard.edu](http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/vitamins/)</sup>

The process of self-diagnosis should not simply be "Do I suffer from scurvy? No; ergo I'm getting all the vitamin C I need." Rather, you should be asking my self "Am I avoiding colon cancer as best I can?" That question is trickier to answer.

**No**, you do not need vitamin supplements if you get sufficient levels of vitamins anyway. There is **no** added benefit to getting *more* than enough vitamins. But I can't generalize that into "eating a healthy and balanced diet", as per your question. First of all, that phrase probably entails different specific details depending on the individual. But more importantly, I'd like to stress that it's not all about your diet. The richest source of vitamin D, for instance, is exposure to the sun.

> If you live north of the line connecting San Francisco to Philadelphia and Athens to Beijing, odds are that you don't get enough vitamin D. The same holds true if you don't get outside for at least a 15-minute daily walk in the sun. African-Americans and others with dark skin, as well as older individuals, tend to have much lower levels of vitamin D, as do people who are overweight or obese. <sup>[* harvard.edu](http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/vitamin-d/index.html)</sup>

It is worth looking into whether or not you belong to any of the risk groups, to assess whether or not you would be in need of supplements, or - perhaps preferrably - a change of habits. For a healthy adult to take *multi-vitamins* sounds to me like hedging your bets, but a pill a day won't get you intoxicated either.