Today, new studies are proving one of them right.
"Some of the best-known brands in America have arsenic in their apple juice," Oz said on his show.
Besser, ABC's chief health and medical editor, challenged Oz and his research on Good Morning America. Their exchange was heated and highly publicized.
"This is fear mongering," Besser charged. "It reminds me of yelling 'fire' in a movie theatre. I'm very annoyed about this."
New evidence appears to be backing Oz: Consumer Reports tested apple and grape juice, including some of America's favorite brands. The results show, out of 88 samples, that 10 percent had total arsenic levels greater than the federal standard for drinking water.
Besser blames the FDA for backpedaling on its original statements that made him so adamant that juice was safe.
"They said there was an industry standard," Besser said. "Turns out, there is not. They said the type of arsenic in apple juice was the safe kind. Turns out that it's not. And to reassure the public, they public the results online so we all can look at it."
Besser said eight results that were very high were withheld from that result.
The FDA released a statement on the Consumer Reports testing that read: "A small percentage of samples contain elevated levels of arsenic. In response, the FDA has expanded our surveillance activities and is collecting additional data."
Consumer Reports also found 25 percent of the juices it tested had lead levels higher than the FDA standard for bottled water. The Juice Products Association says "Juice is not water. To compare the trade levels of arsenic or lead in juice to the regulatory guidelines for drinking water is not appropriate."
Consumer advocates hopes this controversy leads to better guidelines.
"We need to be paying better attention to the results of that process, which his hopefully setting a limit and telling manufacturers of juice to look for these levels and don't exceed the number," said Patty Lovera, the associate director of Food & Water Watch.
In the meantime, Besser's advice to parents is to limit the amount of juice a child drinks anyway, as juice is linked to obesity. Babies under six months old should never drink juice, and no child should drink juice from a bottle.