Do Multivitamins Do More Harm Than Good?

MIAMI (CBSMiami) -- Many people use vitamins to make up for shortcomings in their diets but taking big doses could actually do more harm than good.

Dr. Olveen Carrasquillo, the Chief of General Internal Medicine at the University Of Miami School Of Medicine, told CBS4's Rhiannon Ally, "Leading a healthy lifestyle is difficult."

While taking a multivitamin may help, a new book, "Do you Believe in Magic?" warns that taking supplements in super high doses may be dangerous.

"There are 20 studies that show too much vitamins can actually shorten your life," said author Dr. Paul Offit.

Mega-doses of certain vitamins may increase the risk for heart disease and cancer, according to Dr. Offit. Specifically, doses that are 5, 10, sometimes 20 times greater than the recommended daily allowance for these nutrients.

"By challenging mother nature in taking these vitamins and concentrating them to these exceptionally large quantities that you would never normally eat, you've got to be careful," said Dr. Offit.

Dr. Carrasquillo believes there are certain high doses you need to avoid more than others.

"In general as doctors, we advise the fat soluble vitamins: A,D,E,K, but the evidence is best for limiting vitamin E."

But, he also said moderation is key when taking any vitamin. Unless you are under a doctor's advice to take a higher dose due to a vitamin deficiency.

"A lot of people have vitamin D deficiencies, even places  with a lot of sun and sometimes we'll place people on high doses of vitamin D to replace it, but that's short term, medical monitoring," said Dr. Carrasquillo.

Dr. Carrasquillo and Dr. Offit both say there is no magic pill, but for most people, taking a regular multivitamin is fine, but there is no substitute for eating plenty of fruits and vegetables.