Taking a daily multivitamin may not be worth it in the long run - if your diet covers all the recommended daily nutritional bases. (This requires a diverse mix of fruit and veggies, lean meats, legumes, and whole grains, so if you're a picky eater, a vegetarian, or have a food allergy, you may need a daily pill.)
Don't bother with extra supplements, such as calcium, vitamin C, or vitamin D, unless your doctor recommends them for a specific reason. And you can ditch the vitamin-infused waters and beverages: They're usually high in calories and chemicals, and can do more harm than good.
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