"There isn't a lot of regulation regarding quality control, safety or efficacy," said Hensrud. "It's somewhat of a buyer beware [situation]."
While some supplements are marketed to work for a variety of ailments, there's no scientific data to back all of the claims.
All women of childbearing age are advised to take folic acid to prevent neural tube defects in their child. However, some studies discredit claims that folic acid and other B vitamins prevent prostate cancer, colon cancer or heart disease.
For some, however, supplements can be beneficial, said Ayoob.
In fact, only 3 to 4 percent of Americans follow all of the dietary guidelines, according to 2009 position paper published by the American Dietetic Association.
"Some things are difficult to get [from food] for some people," said Ayoob.
Among those are vitamin D, which most often is gained through appropriate exposure to sunlight, tuna, salmon or fortified milk. Many Americans are deficient in vitamin D, he said.
Other examples include osteoporosis patients who may need calcium supplements, or smokers who are at higher risk for vitamin C deficiency.
Still, Ayoob said, "You're never going to get from a pill what you get from healthy food."