While a healthy diet should provide an adequate source of vitamins, supplementing with a multivitamin acts as a "nutrition insurance policy" to ensure the body receives all the nutrients it needs, explains The Nutrition Source. Taking a daily multivitamin can help protect against certain types of cancers and other chronic diseases.
Many Americans do not get enough essential nutrients such as calcium, potassium, vitamin D, and vitamin B12 in their diets, and a multivitamin supplement can help ensure adequate intake of these nutrients, according to WebMD. Thus, taking a multivitamin supplement can protect against chronic conditions that can develop from vitamin deficiencies. In addition, a daily multivitamin is safer than mixing several individual supplements, which may lead to exceeding the recommended upper limit for a particular nutrient.
Most multivitamins contain folic acid, which helps prevent neural tube defects in neonates in women who take it before becoming pregnant, notes The Nutrition Source. Folic acid may also reduce a person's risk for colon cancer, heart disease and breast cancer. In addition, the Vitamin D in a multivitamin also helps decrease colon cancer risk. Among postmenopausal women, taking a daily multivitamin is associated with increased bone density and reduced fractures, according to WebMD.