I don't recommend taking a break from daily vitamin and mineral supplements. They don't lose their effectiveness, and the body needs the micronutrients they supply daily.
The rationale for taking supplements in the first place is as insurance against nutritional gaps in the diet and as added defense against increasing toxic pressures from the environment. Ideally, your diet should provide most of your nutritional needs, and it can if it is the right diet for you, richly varied, and abundant in fresh vegetables and fruits. However, that is a big "if." Many of the crop varieties grown may not be the most nutritious, and growing methods (including soil management and chemicals) used in their production may deplete nutrients. If you use drugs like alcohol, tobacco, or caffeine, if you are under a great deal of stress, or if you are sick, your need for some micronutrients and protective phytonutrients may be greater than your diet can supply. Because of all these variables, a daily multivitamin and mineral supplement is the best way to ensure that you are getting what you need.
On the flip side, it is also important to remember that vitamins, minerals and other dietary supplements won't make up for an unhealthy, unbalanced diet lacking in fresh fruits and vegetables.
If you're taking herbal supplements on a daily basis, you should be aware that many will lose their effectiveness if you use them all the time or too frequently. Medicinal plants are best viewed as dilute forms of natural drugs, not as foods or dietary supplements. For that reason, you should not take them casually or for no good reason, any more than you would take a pharmaceutical drug casually or for no good reason. When using medicinal herbs, bear in mind that individual responses vary, so it is best to let your experience be your guide and use only remedies and brands that give you consistent and positive results.
The exceptions to the general rule about using medicinal herbs only when needed for a specific purpose are the tonic herbs, or adaptogens, (traditional examples include ginseng and ashwagandha) that may help maintain a normal healing system, and Asian mushrooms that support immune health. Be sure to give any tonic a reasonable trial - take it regularly for at least two months. With some, you'll experience obvious effects - perhaps an increased sense of well-being and more energy. Or you may find that, over time, a tonic improves your response to both physical and emotional stress and decreases your susceptibility to illness.
Andrew Weil, M.D.