Each year, Americans spend billions of dollars on multivitamins. Vitamin buyers tend to make five or six vitamin shopping trips each year. They are a loyal bunch because many people think supplements are the key to good health. But "GMA's" medical correspondent, Dr. David Katz, said that they should only be insurance, not replacements for a healthy diet.
"It's not a substitute for getting you vitamins from fruits and vegetables, but everyone should take them as more of an insurance policy," said Katz, director of the Yale Prevention Research Center. "Realistically, people don't always eat healthily enough to get all the vitamins they need."
Katz said that people should take vitamins tailored to their needs. Women should take vitamins formulated for women and everyone should make sure that they take vitamins are easily absorbed into the body.
"Absorption is the key to a good multivitamin, so it's important to get a pill that dissolves well," he said.
In addition to vitamins, Katz said that people like should take fatty acids like fish oil or for vegetarians, flaxseed oil. Women should take calcium, he said.
However, sometimes, too much of a vitamin may be harmful. Dr. Daniel Hyman, a general internist with Cooper University Hospital in Camden said "overloading on iron can cause liver problems and in males it can cause testicular problems."
Vitamin A can also be toxic in large amounts. Only double the government's current daily value of supplemental vitamin A in the form of retinol can increase the risk of birth defects and liver damage. Large doses of vitamin C can cause gastrointestinal upset, diarrhea and other side effects. Since much of the food we eat is fortified, it is easy to overload on a particular vitamin or mineral if you're also taking daily multivitamins and other supplements.
Often times, vitamins have little or no effect. A study conducted by the U.S. Preventive Services Task Force found that for a healthy adult who regularly eats fruits and vegetables, taking a daily multivitamin or other supplements will not make much of a difference. The body typically excretes excess vitamins -- especially multivitamins, which are particularly susceptible to being flushed because they aren't attached to food.