The Nutrition Source
1. Eat a healthy diet. A multivitamin provides some insurance against deficiencies but is far less important for health than the healthy food patterns described on this website. Choose a diet rich in fruits, vegetables, whole grains, nuts and healthy oils, and low in red meat and unhealthy fats—let the Healthy Eating Pyramid be your guide.
2. Choose a daily multivitamin. A daily multivitamin is an inexpensive nutrition insurance policy. Try to take one every day.
3. Think about D. In addition to its bone health benefits, there’s growing evidence that getting some extra vitamin D can help lower the risk of colon and breast cancer. Aim for getting 1,000 to 2,000 IU of vitamin D per day—this likely will require an extra vitamin D pill, in addition to your multivitamin. For more information, see the vitamin D section of The Nutrition Source.
4. Say no to “megas.” In general, avoid mega-dose vitamins and mega-fortified foods. Higher doses of vitamin E may help to prevent heart disease, but in general, the amount in a standard multivitamin is enough to have health benefits. A standard multivitamin also has a day's worth of folic acid, so you should avoid foods that have high amounts of folic acid added to them. Vitamin D is an exception, as many people need more than the RDA.
5. Avoid “super” supplements. Don’t be swayed by the wild health claims of the many health supplements advertised on TV and the Internet. If they sound too good to true, you can be sure they are. Save your money for healthy food and a good vacation.
Nutrition Insurance Policy: Learn why a multivitamin-multimineral supplement can fill in micronutrient gaps in your diet.
Keep the Multi, Skip the Heavily Fortified Foods: Why you should keep taking a daily
multivitamin but skip foods that are heavily fortified with folic acid.
Antioxidants: Beyond the Hype: What's the buzz around antioxidants—and what's the evidence?
Supplement Studies: Sorting Out the Confusion: How to make sense of the media hype around supplements.
Source : Harvard School of Public Health