By Pat Loeb

PHILADELPHIA (CBS) – A Philadelphia pediatrician is taking on the unregulated vitamin and supplement industry in a new book about alternative medicine.

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Paul Offit doesn’t mind challenging scientifically, suspect medical claims. He’s credited with debunking the theory that vaccines cause autism.

Now the Children’s Hospital Infectious Disease Director is scrutinizing the $68-billion vitamin and dietary supplement market and finds potentially dangerous misconceptions.

“People think that vitamins are safe. They assume that since we clearly do need vitamins, that more is better,” says Offit.

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He says, in fact, numerous studies have shown you can get too much of a good thing, including the much-extolled /anti-oxidants.

“Large quantities of vitamins A, E, beta carotene, selenium, those sorts of things, can increase your risk of cancer, increase your risk of heart disease and shorten your life,” Offit explains.

He details more of what supplements do and don’t do in his book Do You Believe in Magic?: The Sense and Nonsense of Alternative Medicine which is due out Monday.

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Listen to full interview: